android/launcher2/Workspace.java

/*
 * Copyright (C) 2008 The Android Open Source Project
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package com.android.launcher2;

import android.content.Context;
import android.content.Intent;
import android.content.ComponentName;
import android.content.res.TypedArray;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.RectF;
import android.graphics.Rect;
import android.graphics.Region;
import android.graphics.drawable.Drawable;
import android.util.AttributeSet;
import android.util.Log;
import android.view.MotionEvent;
import android.view.VelocityTracker;
import android.view.View;
import android.view.ViewConfiguration;
import android.view.ViewGroup;
import android.view.ViewParent;
import android.widget.Scroller;
import android.widget.TextView;
import android.os.Parcelable;
import android.os.Parcel;

import java.util.ArrayList;

/**
 * The workspace is a wide area with a wallpaper and a finite number of screens. Each
 * screen contains a number of icons, folders or widgets the user can interact with.
 * A workspace is meant to be used with a fixed width only.
 */
public class Workspace extends ViewGroup implements DropTarget, DragSource, DragScroller {
    private static final int INVALID_SCREEN = -1;

    /**
     * The velocity at which a fling gesture will cause us to snap to the next screen
     */
    private static final int SNAP_VELOCITY = 1000;

    private int mDefaultScreen;
    private View mWallpaper;

    private boolean mFirstLayout = true;

    private int mCurrentScreen;
    private int mNextScreen = INVALID_SCREEN;
    private Scroller mScroller;
    private VelocityTracker mVelocityTracker;

    /**
     * CellInfo for the cell that is currently being dragged
     */
    private CellLayout.CellInfo mDragInfo;

    /**
     * Target drop area calculated during last acceptDrop call.
     */
    private int[] mTargetCell = null;

    private float mLastMotionX;
    private float mLastMotionY;

    private final static int TOUCH_STATE_REST = 0;
    private final static int TOUCH_STATE_SCROLLING = 1;

    private int mTouchState = TOUCH_STATE_REST;

    private OnLongClickListener mLongClickListener;

    private Launcher mLauncher;
    private DragController mDragger;

    /**
     * Cache of vacant cells, used during drag events and invalidated as needed.
     */
    private CellLayout.CellInfo mVacantCache = null;

    private int[] mTempCell = new int[2];
    private int[] mTempEstimate = new int[2];

    private boolean mAllowLongPress;
    private boolean mLocked;

    private int mTouchSlop;
    private int mMaximumVelocity;

    final Rect mDrawerBounds = new Rect();
    final Rect mClipBounds = new Rect();
    int mDrawerContentHeight;
    int mDrawerContentWidth;

    /**
     * Used to inflate the Workspace from XML.
     *
     * @param context The application's context.
     * @param attrs The attribtues set containing the Workspace's customization values.
     */
    public Workspace(Context context, AttributeSet attrs) {
        this(context, attrs, 0);
    }

    /**
     * Used to inflate the Workspace from XML.
     *
     * @param context The application's context.
     * @param attrs The attribtues set containing the Workspace's customization values.
     * @param defStyle Unused.
     */
    public Workspace(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);

        TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.Workspace, defStyle, 0);
        mDefaultScreen = a.getInt(R.styleable.Workspace_defaultScreen, 1);
        a.recycle();

        initWorkspace();
    }

    /**
     * Initializes various states for this workspace.
     */
    private void initWorkspace() {
        mScroller = new Scroller(getContext());
        mCurrentScreen = mDefaultScreen;
        Launcher.setScreen(mCurrentScreen);

        final ViewConfiguration configuration = ViewConfiguration.get(getContext());
        mTouchSlop = configuration.getScaledTouchSlop();
        mMaximumVelocity = configuration.getScaledMaximumFlingVelocity();
    }

    void setWallpaper(View wallpaper) {
        mWallpaper = wallpaper;
    }

    @Override
    public void addView(View child, int index, LayoutParams params) {
        if (!(child instanceof CellLayout)) {
            throw new IllegalArgumentException("A Workspace can only have CellLayout children.");
        }
        super.addView(child, index, params);
    }

    @Override
    public void addView(View child) {
        if (!(child instanceof CellLayout)) {
            throw new IllegalArgumentException("A Workspace can only have CellLayout children.");
        }
        super.addView(child);
    }

    @Override
    public void addView(View child, int index) {
        if (!(child instanceof CellLayout)) {
            throw new IllegalArgumentException("A Workspace can only have CellLayout children.");
        }
        super.addView(child, index);
    }

    @Override
    public void addView(View child, int width, int height) {
        if (!(child instanceof CellLayout)) {
            throw new IllegalArgumentException("A Workspace can only have CellLayout children.");
        }
        super.addView(child, width, height);
    }

    @Override
    public void addView(View child, LayoutParams params) {
        if (!(child instanceof CellLayout)) {
            throw new IllegalArgumentException("A Workspace can only have CellLayout children.");
        }
        super.addView(child, params);
    }

    /**
     * @return The open folder on the current screen, or null if there is none
     */
    Folder getOpenFolder() {
        CellLayout currentScreen = (CellLayout) getChildAt(mCurrentScreen);
        int count = currentScreen.getChildCount();
        for (int i = 0; i < count; i++) {
            View child = currentScreen.getChildAt(i);
            CellLayout.LayoutParams lp = (CellLayout.LayoutParams) child.getLayoutParams();
            if (lp.cellHSpan == 4 && lp.cellVSpan == 4 && child instanceof Folder) {
                return (Folder) child;
            }
        }
        return null;
    }

    ArrayList<Folder> getOpenFolders() {
        final int screens = getChildCount();
        ArrayList<Folder> folders = new ArrayList<Folder>(screens);

        for (int screen = 0; screen < screens; screen++) {
            CellLayout currentScreen = (CellLayout) getChildAt(screen);
            int count = currentScreen.getChildCount();
            for (int i = 0; i < count; i++) {
                View child = currentScreen.getChildAt(i);
                CellLayout.LayoutParams lp = (CellLayout.LayoutParams) child.getLayoutParams();
                if (lp.cellHSpan == 4 && lp.cellVSpan == 4 && child instanceof Folder) {
                    folders.add((Folder) child);
                    break;
                }
            }
        }

        return folders;
    }

    boolean isDefaultScreenShowing() {
        return mCurrentScreen == mDefaultScreen;
    }

    /**
     * Returns the index of the currently displayed screen.
     *
     * @return The index of the currently displayed screen.
     */
    int getCurrentScreen() {
        return mCurrentScreen;
    }

    /**
     * Returns how many screens there are.
     */
    int getScreenCount() {
        return getChildCount();
    }

    /**
     * Computes a bounding rectangle for a range of cells
     *
     * @param cellX X coordinate of upper left corner expressed as a cell position
     * @param cellY Y coordinate of upper left corner expressed as a cell position
     * @param cellHSpan Width in cells
     * @param cellVSpan Height in cells
     * @param rect Rectnagle into which to put the results
     */
    public void cellToRect(int cellX, int cellY, int cellHSpan, int cellVSpan, RectF rect) {
        ((CellLayout)getChildAt(mCurrentScreen)).cellToRect(cellX, cellY,
                cellHSpan, cellVSpan, rect);
    }

    /**
     * Sets the current screen.
     *
     * @param currentScreen
     */
    void setCurrentScreen(int currentScreen) {
        clearVacantCache();
        mCurrentScreen = Math.max(0, Math.min(currentScreen, getChildCount() - 1));
        scrollTo(mCurrentScreen * getWidth(), 0);
        invalidate();
    }

    /**
     * Shows the default screen (defined by the firstScreen attribute in XML.)
     */
    void showDefaultScreen() {
        setCurrentScreen(mDefaultScreen);
    }

    /**
     * Adds the specified child in the current screen. The position and dimension of
     * the child are defined by x, y, spanX and spanY.
     *
     * @param child The child to add in one of the workspace's screens.
     * @param x The X position of the child in the screen's grid.
     * @param y The Y position of the child in the screen's grid.
     * @param spanX The number of cells spanned horizontally by the child.
     * @param spanY The number of cells spanned vertically by the child.
     */
    void addInCurrentScreen(View child, int x, int y, int spanX, int spanY) {
        addInScreen(child, mCurrentScreen, x, y, spanX, spanY, false);
    }

    /**
     * Adds the specified child in the current screen. The position and dimension of
     * the child are defined by x, y, spanX and spanY.
     *
     * @param child The child to add in one of the workspace's screens.
     * @param x The X position of the child in the screen's grid.
     * @param y The Y position of the child in the screen's grid.
     * @param spanX The number of cells spanned horizontally by the child.
     * @param spanY The number of cells spanned vertically by the child.
     * @param insert When true, the child is inserted at the beginning of the children list.
     */
    void addInCurrentScreen(View child, int x, int y, int spanX, int spanY, boolean insert) {
        addInScreen(child, mCurrentScreen, x, y, spanX, spanY, insert);
    }

    /**
     * Adds the specified child in the specified screen. The position and dimension of
     * the child are defined by x, y, spanX and spanY.
     *
     * @param child The child to add in one of the workspace's screens.
     * @param screen The screen in which to add the child.
     * @param x The X position of the child in the screen's grid.
     * @param y The Y position of the child in the screen's grid.
     * @param spanX The number of cells spanned horizontally by the child.
     * @param spanY The number of cells spanned vertically by the child.
     */
    void addInScreen(View child, int screen, int x, int y, int spanX, int spanY) {
        addInScreen(child, screen, x, y, spanX, spanY, false);
    }

    /**
     * Adds the specified child in the specified screen. The position and dimension of
     * the child are defined by x, y, spanX and spanY.
     *
     * @param child The child to add in one of the workspace's screens.
     * @param screen The screen in which to add the child.
     * @param x The X position of the child in the screen's grid.
     * @param y The Y position of the child in the screen's grid.
     * @param spanX The number of cells spanned horizontally by the child.
     * @param spanY The number of cells spanned vertically by the child.
     * @param insert When true, the child is inserted at the beginning of the children list.
     */
    void addInScreen(View child, int screen, int x, int y, int spanX, int spanY, boolean insert) {
        if (screen < 0 || screen >= getChildCount()) {
            throw new IllegalStateException("The screen must be >= 0 and < " + getChildCount());
        }

        clearVacantCache();

        final CellLayout group = (CellLayout) getChildAt(screen);
        CellLayout.LayoutParams lp = (CellLayout.LayoutParams) child.getLayoutParams();
        if (lp == null) {
            lp = new CellLayout.LayoutParams(x, y, spanX, spanY);
        } else {
            lp.cellX = x;
            lp.cellY = y;
            lp.cellHSpan = spanX;
            lp.cellVSpan = spanY;
        }
        group.addView(child, insert ? 0 : -1, lp);
        if (!(child instanceof Folder)) {
            child.setOnLongClickListener(mLongClickListener);
        }
    }

    void addWidget(View view, Widget widget) {
        addInScreen(view, widget.screen, widget.cellX, widget.cellY, widget.spanX,
                widget.spanY, false);
    }

    void addWidget(View view, Widget widget, boolean insert) {
        addInScreen(view, widget.screen, widget.cellX, widget.cellY, widget.spanX,
                widget.spanY, insert);
    }

    CellLayout.CellInfo findAllVacantCells(boolean[] occupied) {
        CellLayout group = (CellLayout) getChildAt(mCurrentScreen);
        if (group != null) {
            return group.findAllVacantCells(occupied, null);
        }
        return null;
    }

    private void clearVacantCache() {
        if (mVacantCache != null) {
            mVacantCache.clearVacantCells();
            mVacantCache = null;
        }
    }

    /**
     * Returns the coordinate of a vacant cell for the current screen.
     */
    boolean getVacantCell(int[] vacant, int spanX, int spanY) {
        CellLayout group = (CellLayout) getChildAt(mCurrentScreen);
        if (group != null) {
            return group.getVacantCell(vacant, spanX, spanY);
        }
        return false;
    }

    /**
     * Adds the specified child in the current screen. The position and dimension of
     * the child are defined by x, y, spanX and spanY.
     *
     * @param child The child to add in one of the workspace's screens.
     * @param spanX The number of cells spanned horizontally by the child.
     * @param spanY The number of cells spanned vertically by the child.
     */
    void fitInCurrentScreen(View child, int spanX, int spanY) {
        fitInScreen(child, mCurrentScreen, spanX, spanY);
    }

    /**
     * Adds the specified child in the specified screen. The position and dimension of
     * the child are defined by x, y, spanX and spanY.
     *
     * @param child The child to add in one of the workspace's screens.
     * @param screen The screen in which to add the child.
     * @param spanX The number of cells spanned horizontally by the child.
     * @param spanY The number of cells spanned vertically by the child.
     */
    void fitInScreen(View child, int screen, int spanX, int spanY) {
        if (screen < 0 || screen >= getChildCount()) {
            throw new IllegalStateException("The screen must be >= 0 and < " + getChildCount());
        }

        final CellLayout group = (CellLayout) getChildAt(screen);
        boolean vacant = group.getVacantCell(mTempCell, spanX, spanY);
        if (vacant) {
            group.addView(child,
                    new CellLayout.LayoutParams(mTempCell[0], mTempCell[1], spanX, spanY));
            child.setOnLongClickListener(mLongClickListener);
            if (!(child instanceof Folder)) {
                child.setOnLongClickListener(mLongClickListener);
            }
        }
    }

    /**
     * Registers the specified listener on each screen contained in this workspace.
     *
     * @param l The listener used to respond to long clicks.
     */
    @Override
    public void setOnLongClickListener(OnLongClickListener l) {
        mLongClickListener = l;
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).setOnLongClickListener(l);
        }
    }

    @Override
    public void computeScroll() {
        if (mScroller.computeScrollOffset()) {
            mScrollX = mScroller.getCurrX();
            mScrollY = mScroller.getCurrY();
            mWallpaper.scrollTo(mScrollX, mScrollY);
            postInvalidate();
        } else if (mNextScreen != INVALID_SCREEN) {
            mCurrentScreen = Math.max(0, Math.min(mNextScreen, getChildCount() - 1));
            Launcher.setScreen(mCurrentScreen);
            mNextScreen = INVALID_SCREEN;
            clearChildrenCache();
        }
    }

    @Override
    protected void dispatchDraw(Canvas canvas) {
        boolean restore = false;

        // ViewGroup.dispatchDraw() supports many features we don't need:
        // clip to padding, layout animation, animation listener, disappearing
        // children, etc. The following implementation attempts to fast-track
        // the drawing dispatch by drawing only what we know needs to be drawn.

        boolean fastDraw = mTouchState != TOUCH_STATE_SCROLLING && mNextScreen == INVALID_SCREEN;
        // If we are not scrolling or flinging, draw only the current screen
        if (fastDraw) {
            drawChild(canvas, getChildAt(mCurrentScreen), getDrawingTime());
        } else {
            final long drawingTime = getDrawingTime();
            // If we are flinging, draw only the current screen and the target screen
            if (mNextScreen >= 0 && mNextScreen < getChildCount() &&
                    Math.abs(mCurrentScreen - mNextScreen) == 1) {
                drawChild(canvas, getChildAt(mCurrentScreen), drawingTime);
                drawChild(canvas, getChildAt(mNextScreen), drawingTime);
            } else {
                // If we are scrolling, draw all of our children
                final int count = getChildCount();
                for (int i = 0; i < count; i++) {
                    drawChild(canvas, getChildAt(i), drawingTime);
                }
            }
        }

        if (restore) {
            canvas.restore();
        }
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);

        final int width = MeasureSpec.getSize(widthMeasureSpec);
        final int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        if (widthMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("Workspace can only be used in EXACTLY mode.");
        }

        final int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        if (heightMode != MeasureSpec.EXACTLY) {
            throw new IllegalStateException("Workspace can only be used in EXACTLY mode.");
        }

        // The children are given the same width and height as the workspace
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            getChildAt(i).measure(widthMeasureSpec, heightMeasureSpec);
        }

        if (mFirstLayout) {
            scrollTo(mCurrentScreen * width, 0);
            mFirstLayout = false;
        }
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        int childLeft = 0;

        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final View child = getChildAt(i);
            if (child.getVisibility() != View.GONE) {
                final int childWidth = child.getMeasuredWidth();
                child.layout(childLeft, 0, childLeft + childWidth, child.getMeasuredHeight());
                childLeft += childWidth;
            }
        }
    }

    @Override
    public boolean requestChildRectangleOnScreen(View child, Rect rectangle, boolean immediate) {
        int screen = indexOfChild(child);
        if (screen != mCurrentScreen || !mScroller.isFinished()) {
            if (!mLauncher.isWorkspaceLocked()) {
                snapToScreen(screen);
            }
            return true;
        }
        return false;
    }

    @Override
    protected boolean onRequestFocusInDescendants(int direction, Rect previouslyFocusedRect) {
        if (mLauncher.isDrawerDown()) {
            final Folder openFolder = getOpenFolder();
            if (openFolder != null) {
                return openFolder.requestFocus(direction, previouslyFocusedRect);
            } else {
                int focusableScreen;
                if (mNextScreen != INVALID_SCREEN) {
                    focusableScreen = mNextScreen;
                } else {
                    focusableScreen = mCurrentScreen;
                }
                getChildAt(focusableScreen).requestFocus(direction, previouslyFocusedRect);
            }
        }
        return false;
    }

    @Override
    public boolean dispatchUnhandledMove(View focused, int direction) {
        if (direction == View.FOCUS_LEFT) {
            if (getCurrentScreen() > 0) {
                snapToScreen(getCurrentScreen() - 1);
                return true;
            }
        } else if (direction == View.FOCUS_RIGHT) {
            if (getCurrentScreen() < getChildCount() - 1) {
                snapToScreen(getCurrentScreen() + 1);
                return true;
            }
        }
        return super.dispatchUnhandledMove(focused, direction);
    }

    @Override
    public void addFocusables(ArrayList<View> views, int direction, int focusableMode) {
        if (mLauncher.isDrawerDown()) {
            final Folder openFolder = getOpenFolder();
            if (openFolder == null) {
                getChildAt(mCurrentScreen).addFocusables(views, direction);
                if (direction == View.FOCUS_LEFT) {
                    if (mCurrentScreen > 0) {
                        getChildAt(mCurrentScreen - 1).addFocusables(views, direction);
                    }
                } else if (direction == View.FOCUS_RIGHT){
                    if (mCurrentScreen < getChildCount() - 1) {
                        getChildAt(mCurrentScreen + 1).addFocusables(views, direction);
                    }
                }
            } else {
                openFolder.addFocusables(views, direction);
            }
        }
    }

    @Override
    public boolean onInterceptTouchEvent(MotionEvent ev) {
        if (mLocked || !mLauncher.isDrawerDown()) {
            return true;
        }

        /*
         * This method JUST determines whether we want to intercept the motion.
         * If we return true, onTouchEvent will be called and we do the actual
         * scrolling there.
         */

        /*
         * Shortcut the most recurring case: the user is in the dragging
         * state and he is moving his finger.  We want to intercept this
         * motion.
         */
        final int action = ev.getAction();
        if ((action == MotionEvent.ACTION_MOVE) && (mTouchState != TOUCH_STATE_REST)) {
            return true;
        }

        final float x = ev.getX();
        final float y = ev.getY();

        switch (action) {
            case MotionEvent.ACTION_MOVE:
                /*
                 * mIsBeingDragged == false, otherwise the shortcut would have caught it. Check
                 * whether the user has moved far enough from his original down touch.
                 */

                /*
                 * Locally do absolute value. mLastMotionX is set to the y value
                 * of the down event.
                 */
                final int xDiff = (int) Math.abs(x - mLastMotionX);
                final int yDiff = (int) Math.abs(y - mLastMotionY);

                final int touchSlop = mTouchSlop;
                boolean xMoved = xDiff > touchSlop;
                boolean yMoved = yDiff > touchSlop;

                if (xMoved || yMoved) {

                    if (xMoved) {
                        // Scroll if the user moved far enough along the X axis
                        mTouchState = TOUCH_STATE_SCROLLING;
                        enableChildrenCache();
                    }
                    // Either way, cancel any pending longpress
                    if (mAllowLongPress) {
                        mAllowLongPress = false;
                        // Try canceling the long press. It could also have been scheduled
                        // by a distant descendant, so use the mAllowLongPress flag to block
                        // everything
                        final View currentScreen = getChildAt(mCurrentScreen);
                        currentScreen.cancelLongPress();
                    }
                }
                break;

            case MotionEvent.ACTION_DOWN:
                // Remember location of down touch
                mLastMotionX = x;
                mLastMotionY = y;
                mAllowLongPress = true;

                /*
                 * If being flinged and user touches the screen, initiate drag;
                 * otherwise don't.  mScroller.isFinished should be false when
                 * being flinged.
                 */
                mTouchState = mScroller.isFinished() ? TOUCH_STATE_REST : TOUCH_STATE_SCROLLING;
                break;

            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                // Release the drag
                clearChildrenCache();
                mTouchState = TOUCH_STATE_REST;
                mAllowLongPress = false;
                break;
        }

        /*
         * The only time we want to intercept motion events is if we are in the
         * drag mode.
         */
        return mTouchState != TOUCH_STATE_REST;
    }

    void enableChildrenCache() {
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final CellLayout layout = (CellLayout) getChildAt(i);
            layout.setChildrenDrawnWithCacheEnabled(true);
            layout.setChildrenDrawingCacheEnabled(true);
        }
    }

    void clearChildrenCache() {
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final CellLayout layout = (CellLayout) getChildAt(i);
            layout.setChildrenDrawnWithCacheEnabled(false);
        }
    }

    @Override
    public boolean onTouchEvent(MotionEvent ev) {

        if (mLocked || !mLauncher.isDrawerDown()) {
            return true;
        }

        if (mVelocityTracker == null) {
            mVelocityTracker = VelocityTracker.obtain();
        }
        mVelocityTracker.addMovement(ev);

        final int action = ev.getAction();
        final float x = ev.getX();

        switch (action) {
        case MotionEvent.ACTION_DOWN:
            /*
             * If being flinged and user touches, stop the fling. isFinished
             * will be false if being flinged.
             */
            if (!mScroller.isFinished()) {
                mScroller.abortAnimation();
            }

            // Remember where the motion event started
            mLastMotionX = x;
            break;
        case MotionEvent.ACTION_MOVE:
            if (mTouchState == TOUCH_STATE_SCROLLING) {
                // Scroll to follow the motion event
                final int deltaX = (int) (mLastMotionX - x);
                mLastMotionX = x;

                if (deltaX < 0) {
                    if (mScrollX > 0) {
                        scrollBy(Math.max(-mScrollX, deltaX), 0);
                        mWallpaper.scrollTo(mScrollX, mScrollY);
                    }
                } else if (deltaX > 0) {
                    final int availableToScroll = getChildAt(getChildCount() - 1).getRight() -
                            mScrollX - getWidth();
                    if (availableToScroll > 0) {
                        scrollBy(Math.min(availableToScroll, deltaX), 0);
                        mWallpaper.scrollTo(mScrollX, mScrollY);
                    }
                }
            }
            break;
        case MotionEvent.ACTION_UP:
            if (mTouchState == TOUCH_STATE_SCROLLING) {
                final VelocityTracker velocityTracker = mVelocityTracker;
                velocityTracker.computeCurrentVelocity(1000, mMaximumVelocity);
                int velocityX = (int) velocityTracker.getXVelocity();

                if (velocityX > SNAP_VELOCITY && mCurrentScreen > 0) {
                    // Fling hard enough to move left
                    snapToScreen(mCurrentScreen - 1);
                } else if (velocityX < -SNAP_VELOCITY && mCurrentScreen < getChildCount() - 1) {
                    // Fling hard enough to move right
                    snapToScreen(mCurrentScreen + 1);
                } else {
                    snapToDestination();
                }

                if (mVelocityTracker != null) {
                    mVelocityTracker.recycle();
                    mVelocityTracker = null;
                }
            }
            mTouchState = TOUCH_STATE_REST;
            break;
        case MotionEvent.ACTION_CANCEL:
            mTouchState = TOUCH_STATE_REST;
        }

        return true;
    }

    private void snapToDestination() {
        final int screenWidth = getWidth();
        final int whichScreen = (mScrollX + (screenWidth / 2)) / screenWidth;

        snapToScreen(whichScreen);
    }

    void snapToScreen(int whichScreen) {
        if (!mScroller.isFinished()) return;

        clearVacantCache();
        enableChildrenCache();

        whichScreen = Math.max(0, Math.min(whichScreen, getChildCount() - 1));
        boolean changingScreens = whichScreen != mCurrentScreen;

        mNextScreen = whichScreen;

        View focusedChild = getFocusedChild();
        if (focusedChild != null && changingScreens && focusedChild == getChildAt(mCurrentScreen)) {
            focusedChild.clearFocus();
        }

        final int newX = whichScreen * getWidth();
        final int delta = newX - mScrollX;
        mScroller.startScroll(mScrollX, 0, delta, 0, Math.abs(delta) * 2);
        invalidate();
    }

    void startDrag(CellLayout.CellInfo cellInfo) {
        View child = cellInfo.cell;

        // Make sure the drag was started by a long press as opposed to a long click.
        // Note that Search takes focus when clicked rather than entering touch mode
        if (!child.isInTouchMode() && !(child instanceof Search)) {
            return;
        }

        mDragInfo = cellInfo;
        mDragInfo.screen = mCurrentScreen;

        CellLayout current = ((CellLayout) getChildAt(mCurrentScreen));

        current.onDragChild(child);
        mDragger.startDrag(child, this, child.getTag(), DragController.DRAG_ACTION_MOVE);
        invalidate();
    }

    @Override
    protected Parcelable onSaveInstanceState() {
        final SavedState state = new SavedState(super.onSaveInstanceState());
        state.currentScreen = mCurrentScreen;
        return state;
    }

    @Override
    protected void onRestoreInstanceState(Parcelable state) {
        SavedState savedState = (SavedState) state;
        super.onRestoreInstanceState(savedState.getSuperState());
        if (savedState.currentScreen != -1) {
            mCurrentScreen = savedState.currentScreen;
            Launcher.setScreen(mCurrentScreen);
        }
    }

    void addApplicationShortcut(ApplicationInfo info, CellLayout.CellInfo cellInfo) {
        addApplicationShortcut(info, cellInfo, false);
    }

    void addApplicationShortcut(ApplicationInfo info, CellLayout.CellInfo cellInfo,
            boolean insertAtFirst) {
        final CellLayout layout = (CellLayout) getChildAt(cellInfo.screen);
        final int[] result = new int[2];

        layout.cellToPoint(cellInfo.cellX, cellInfo.cellY, result);
        onDropExternal(result[0], result[1], info, layout, insertAtFirst);
    }

    public void onDrop(DragSource source, int x, int y, int xOffset, int yOffset, Object dragInfo) {
        final CellLayout cellLayout = getCurrentDropLayout();
        if (source != this) {
            onDropExternal(x - xOffset, y - yOffset, dragInfo, cellLayout);
        } else {
            // Move internally
            if (mDragInfo != null) {
                final View cell = mDragInfo.cell;
                if (mCurrentScreen != mDragInfo.screen) {
                    final CellLayout originalCellLayout = (CellLayout) getChildAt(mDragInfo.screen);
                    originalCellLayout.removeView(cell);
                    cellLayout.addView(cell);
                }
                mTargetCell = estimateDropCell(x - xOffset, y - yOffset,
                        mDragInfo.spanX, mDragInfo.spanY, cell, cellLayout, mTargetCell);
                cellLayout.onDropChild(cell, mTargetCell);

                final ItemInfo info = (ItemInfo)cell.getTag();
                CellLayout.LayoutParams lp = (CellLayout.LayoutParams) cell.getLayoutParams();
                LauncherModel.moveItemInDatabase(mLauncher, info,
                        LauncherSettings.Favorites.CONTAINER_DESKTOP, mCurrentScreen, lp.cellX, lp.cellY);
            }
        }
    }

    public void onDragEnter(DragSource source, int x, int y, int xOffset, int yOffset,
            Object dragInfo) {
        clearVacantCache();
    }

    public void onDragOver(DragSource source, int x, int y, int xOffset, int yOffset,
            Object dragInfo) {
    }

    public void onDragExit(DragSource source, int x, int y, int xOffset, int yOffset,
            Object dragInfo) {
        clearVacantCache();
    }

    private void onDropExternal(int x, int y, Object dragInfo, CellLayout cellLayout) {
        onDropExternal(x, y, dragInfo, cellLayout, false);
    }

    private void onDropExternal(int x, int y, Object dragInfo, CellLayout cellLayout,
            boolean insertAtFirst) {
        // Drag from somewhere else
        ItemInfo info = (ItemInfo) dragInfo;

        View view;

        switch (info.itemType) {
        case LauncherSettings.Favorites.ITEM_TYPE_APPLICATION:
        case LauncherSettings.Favorites.ITEM_TYPE_SHORTCUT:
            if (info.container == NO_ID) {
                // Came from all apps -- make a copy
                info = new ApplicationInfo((ApplicationInfo) info);
            }
            view = mLauncher.createShortcut(R.layout.application, cellLayout,
                    (ApplicationInfo) info);
            break;
        case LauncherSettings.Favorites.ITEM_TYPE_USER_FOLDER:
            view = FolderIcon.fromXml(R.layout.folder_icon, mLauncher,
                    (ViewGroup) getChildAt(mCurrentScreen), ((UserFolderInfo) info));
            break;
        default:
            throw new IllegalStateException("Unknown item type: " + info.itemType);
        }

        cellLayout.addView(view, insertAtFirst ? 0 : -1);
        view.setOnLongClickListener(mLongClickListener);
        mTargetCell = estimateDropCell(x, y, 1, 1, view, cellLayout, mTargetCell);
        cellLayout.onDropChild(view, mTargetCell);
        CellLayout.LayoutParams lp = (CellLayout.LayoutParams) view.getLayoutParams();

        final LauncherModel model = Launcher.getModel();
        model.addDesktopItem(info);
        LauncherModel.addOrMoveItemInDatabase(mLauncher, info,
                LauncherSettings.Favorites.CONTAINER_DESKTOP, mCurrentScreen, lp.cellX, lp.cellY);
    }

    /**
     * Return the current {@link CellLayout}, correctly picking the destination
     * screen while a scroll is in progress.
     */
    private CellLayout getCurrentDropLayout() {
        int index = mScroller.isFinished() ? mCurrentScreen : mNextScreen;
        return (CellLayout) getChildAt(index);
    }

    /**
     * {@inheritDoc}
     */
    public boolean acceptDrop(DragSource source, int x, int y,
            int xOffset, int yOffset, Object dragInfo) {
        final CellLayout layout = getCurrentDropLayout();
        final CellLayout.CellInfo cellInfo = mDragInfo;
        final int spanX = cellInfo == null ? 1 : cellInfo.spanX;
        final int spanY = cellInfo == null ? 1 : cellInfo.spanY;

        if (mVacantCache == null) {
            final View ignoreView = cellInfo == null ? null : cellInfo.cell;
            mVacantCache = layout.findAllVacantCells(null, ignoreView);
        }

        return mVacantCache.findCellForSpan(mTempEstimate, spanX, spanY, false);
    }

    /**
     * {@inheritDoc}
     */
    public Rect estimateDropLocation(DragSource source, int x, int y,
            int xOffset, int yOffset, Object dragInfo, Rect recycle) {
        final CellLayout layout = getCurrentDropLayout();

        final CellLayout.CellInfo cellInfo = mDragInfo;
        final int spanX = cellInfo == null ? 1 : cellInfo.spanX;
        final int spanY = cellInfo == null ? 1 : cellInfo.spanY;
        final View ignoreView = cellInfo == null ? null : cellInfo.cell;

        final Rect location = recycle != null ? recycle : new Rect();

        // Find drop cell and convert into rectangle
        int[] dropCell = estimateDropCell(x - xOffset, y - yOffset,
                spanX, spanY, ignoreView, layout, mTempCell);

        if (dropCell == null) {
            return null;
        }

        layout.cellToPoint(dropCell[0], dropCell[1], mTempEstimate);
        location.left = mTempEstimate[0];
        location.top = mTempEstimate[1];

        layout.cellToPoint(dropCell[0] + spanX, dropCell[1] + spanY, mTempEstimate);
        location.right = mTempEstimate[0];
        location.bottom = mTempEstimate[1];

        return location;
    }

    /**
     * Calculate the nearest cell where the given object would be dropped.
     */
    private int[] estimateDropCell(int pixelX, int pixelY,
            int spanX, int spanY, View ignoreView, CellLayout layout, int[] recycle) {
        // Create vacant cell cache if none exists
        if (mVacantCache == null) {
            mVacantCache = layout.findAllVacantCells(null, ignoreView);
        }

        // Find the best target drop location
        return layout.findNearestVacantArea(pixelX, pixelY,
                spanX, spanY, mVacantCache, recycle);
    }

    void setLauncher(Launcher launcher) {
        mLauncher = launcher;
    }

    public void setDragger(DragController dragger) {
        mDragger = dragger;
    }

    public void onDropCompleted(View target, boolean success) {
        if (success){
            if (target != this && mDragInfo != null) {
                final CellLayout cellLayout = (CellLayout) getChildAt(mDragInfo.screen);
                cellLayout.removeView(mDragInfo.cell);
                final Object tag = mDragInfo.cell.getTag();
                Launcher.getModel().removeDesktopItem((ItemInfo) tag);
            }
        } else {
            if (mDragInfo != null) {
                final CellLayout cellLayout = (CellLayout) getChildAt(mDragInfo.screen);
                cellLayout.onDropAborted(mDragInfo.cell);
            }
        }

        mDragInfo = null;
    }

    public void scrollLeft() {
        clearVacantCache();
        if (mNextScreen == INVALID_SCREEN && mCurrentScreen > 0 && mScroller.isFinished()) {
            snapToScreen(mCurrentScreen - 1);
        }
    }

    public void scrollRight() {
        clearVacantCache();
        if (mNextScreen == INVALID_SCREEN && mCurrentScreen < getChildCount() -1 &&
                mScroller.isFinished()) {
            snapToScreen(mCurrentScreen + 1);
        }
    }

    public int getScreenForView(View v) {
        int result = -1;
        if (v != null) {
            ViewParent vp = v.getParent();
            int count = getChildCount();
            for (int i = 0; i < count; i++) {
                if (vp == getChildAt(i)) {
                    return i;
                }
            }
        }
        return result;
    }

    /**
     * Find a search widget on the given screen
     */
    private Search findSearchWidget(CellLayout screen) {
        final int count = screen.getChildCount();
        for (int i = 0; i < count; i++) {
            View v = screen.getChildAt(i);
            if (v instanceof Search) {
                return (Search) v;
            }
        }
        return null;
    }

    /**
     * Gets the first search widget on the current screen, if there is one.
     * Returns <code>null</code> otherwise.
     */
    public Search findSearchWidgetOnCurrentScreen() {
        CellLayout currentScreen = (CellLayout)getChildAt(mCurrentScreen);
        return findSearchWidget(currentScreen);
    }

    public Folder getFolderForTag(Object tag) {
        int screenCount = getChildCount();
        for (int screen = 0; screen < screenCount; screen++) {
            CellLayout currentScreen = ((CellLayout) getChildAt(screen));
            int count = currentScreen.getChildCount();
            for (int i = 0; i < count; i++) {
                View child = currentScreen.getChildAt(i);
                CellLayout.LayoutParams lp = (CellLayout.LayoutParams) child.getLayoutParams();
                if (lp.cellHSpan == 4 && lp.cellVSpan == 4 && child instanceof Folder) {
                    Folder f = (Folder) child;
                    if (f.getInfo() == tag) {
                        return f;
                    }
                }
            }
        }
        return null;
    }

    public View getViewForTag(Object tag) {
        int screenCount = getChildCount();
        for (int screen = 0; screen < screenCount; screen++) {
            CellLayout currentScreen = ((CellLayout) getChildAt(screen));
            int count = currentScreen.getChildCount();
            for (int i = 0; i < count; i++) {
                View child = currentScreen.getChildAt(i);
                if (child.getTag() == tag) {
                    return child;
                }
            }
        }
        return null;
    }

    /**
     * Unlocks the SlidingDrawer so that touch events are processed.
     *
     * @see #lock()
     */
    public void unlock() {
        mLocked = false;
    }

    /**
     * Locks the SlidingDrawer so that touch events are ignores.
     *
     * @see #unlock()
     */
    public void lock() {
        mLocked = true;
    }

    /**
     * @return True is long presses are still allowed for the current touch
     */
    public boolean allowLongPress() {
        return mAllowLongPress;
    }

    /**
     * Set true to allow long-press events to be triggered, usually checked by
     * {@link Launcher} to accept or block dpad-initiated long-presses.
     */
    public void setAllowLongPress(boolean allowLongPress) {
        mAllowLongPress = allowLongPress;
    }

    void removeShortcutsForPackage(String packageName) {
        final ArrayList<View> childrenToRemove = new ArrayList<View>();
        final LauncherModel model = Launcher.getModel();
        final int count = getChildCount();

        for (int i = 0; i < count; i++) {
            final CellLayout layout = (CellLayout) getChildAt(i);
            int childCount = layout.getChildCount();

            childrenToRemove.clear();

            for (int j = 0; j < childCount; j++) {
                final View view = layout.getChildAt(j);
                Object tag = view.getTag();

                if (tag instanceof ApplicationInfo) {
                    final ApplicationInfo info = (ApplicationInfo) tag;
                    // We need to check for ACTION_MAIN otherwise getComponent() might
                    // return null for some shortcuts (for instance, for shortcuts to
                    // web pages.)
                    final Intent intent = info.intent;
                    final ComponentName name = intent.getComponent();

                    if (Intent.ACTION_MAIN.equals(intent.getAction()) &&
                            name != null && packageName.equals(name.getPackageName())) {
                        model.removeDesktopItem(info);
                        LauncherModel.deleteItemFromDatabase(mLauncher, info);
                        childrenToRemove.add(view);
                    }
                } else if (tag instanceof UserFolderInfo) {
                    final UserFolderInfo info = (UserFolderInfo) tag;
                    final ArrayList<ApplicationInfo> contents = info.contents;
                    final ArrayList<ApplicationInfo> toRemove = new ArrayList<ApplicationInfo>(1);
                    final int contentsCount = contents.size();
                    boolean removedFromFolder = false;

                    for (int k = 0; k < contentsCount; k++) {
                        final ApplicationInfo appInfo = contents.get(k);
                        final Intent intent = appInfo.intent;
                        final ComponentName name = intent.getComponent();

                        if (Intent.ACTION_MAIN.equals(intent.getAction()) &&
                                name != null && packageName.equals(name.getPackageName())) {
                            toRemove.add(appInfo);
                            LauncherModel.deleteItemFromDatabase(mLauncher, appInfo);
                            removedFromFolder = true;
                        }
                    }

                    contents.removeAll(toRemove);
                    if (removedFromFolder) {
                        final Folder folder = getOpenFolder();
                        if (folder != null) folder.notifyDataSetChanged();
                    }
                }
            }

            childCount = childrenToRemove.size();
            for (int j = 0; j < childCount; j++) {
                layout.removeViewInLayout(childrenToRemove.get(j));
            }

            if (childCount > 0) {
                layout.requestLayout();
                layout.invalidate();
            }
        }
    }

    void updateShortcutsForPackage(String packageName) {
        final int count = getChildCount();
        for (int i = 0; i < count; i++) {
            final CellLayout layout = (CellLayout) getChildAt(i);
            int childCount = layout.getChildCount();
            for (int j = 0; j < childCount; j++) {
                final View view = layout.getChildAt(j);
                Object tag = view.getTag();
                if (tag instanceof ApplicationInfo) {
                    ApplicationInfo info = (ApplicationInfo) tag;
                    // We need to check for ACTION_MAIN otherwise getComponent() might
                    // return null for some shortcuts (for instance, for shortcuts to
                    // web pages.)
                    final Intent intent = info.intent;
                    final ComponentName name = intent.getComponent();
                    if (info.itemType == LauncherSettings.Favorites.ITEM_TYPE_APPLICATION &&
                            Intent.ACTION_MAIN.equals(intent.getAction()) && name != null &&
                            packageName.equals(name.getPackageName())) {

                        final Drawable icon = Launcher.getModel().getApplicationInfoIcon(
                                mLauncher.getPackageManager(), info);
                        if (icon != null && icon != info.icon) {
                            info.icon.setCallback(null);
                            info.icon = Utilities.createIconThumbnail(icon, mContext);
                            info.filtered = true;
                            ((TextView) view).setCompoundDrawablesWithIntrinsicBounds(null,
                                    info.icon, null, null);
                        }
                    }
                }
            }
        }
    }

    void moveToDefaultScreen() {
        snapToScreen(mDefaultScreen);
        getChildAt(mDefaultScreen).requestFocus();
    }

    public static class SavedState extends BaseSavedState {
        int currentScreen = -1;

        SavedState(Parcelable superState) {
            super(superState);
        }

        private SavedState(Parcel in) {
            super(in);
            currentScreen = in.readInt();
        }

        @Override
        public void writeToParcel(Parcel out, int flags) {
            super.writeToParcel(out, flags);
            out.writeInt(currentScreen);
        }

        public static final Parcelable.Creator<SavedState> CREATOR =
                new Parcelable.Creator<SavedState>() {
            public SavedState createFromParcel(Parcel in) {
                return new SavedState(in);
            }

            public SavedState[] newArray(int size) {
                return new SavedState[size];
            }
        };
    }
}