1/*
2 * Copyright (C) 2010 The Android Open Source Project
3 *
4 * Licensed under the Apache License, Version 2.0 (the "License");
5 * you may not use this file except in compliance with the License.
6 * You may obtain a copy of the License at
7 *
8 *      http://www.apache.org/licenses/LICENSE-2.0
9 *
10 * Unless required by applicable law or agreed to in writing, software
11 * distributed under the License is distributed on an "AS IS" BASIS,
12 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
13 * See the License for the specific language governing permissions and
14 * limitations under the License.
15 */
16
17package com.android.launcher3;
18
19import android.content.Context;
20import android.util.AttributeSet;
21import android.view.MotionEvent;
22import android.view.View;
23
24
25/* Class that does most of the work of enabling dragging items out of a PagedView by performing a
26 * vertical drag. Used by both CustomizePagedView and AllAppsPagedView.
27 * Subclasses must do the following:
28 *   * call setDragSlopeThreshold after making an instance of the PagedViewWithDraggableItems
29 *   * call child.setOnLongClickListener(this) and child.setOnTouchListener(this) on all children
30 *       (good place to do it is in syncPageItems)
31 *   * override beginDragging(View) (but be careful to call super.beginDragging(View)
32 *
33 */
34public abstract class PagedViewWithDraggableItems extends PagedView
35    implements View.OnLongClickListener, View.OnTouchListener {
36    private View mLastTouchedItem;
37    private boolean mIsDragging;
38    private boolean mIsDragEnabled;
39    private float mDragSlopeThreshold;
40    private Launcher mLauncher;
41
42    public PagedViewWithDraggableItems(Context context) {
43        this(context, null);
44    }
45
46    public PagedViewWithDraggableItems(Context context, AttributeSet attrs) {
47        this(context, attrs, 0);
48    }
49
50    public PagedViewWithDraggableItems(Context context, AttributeSet attrs, int defStyle) {
51        super(context, attrs, defStyle);
52        mLauncher = (Launcher) context;
53    }
54
55    protected boolean beginDragging(View v) {
56        boolean wasDragging = mIsDragging;
57        mIsDragging = true;
58        return !wasDragging;
59    }
60
61    protected void cancelDragging() {
62        mIsDragging = false;
63        mLastTouchedItem = null;
64        mIsDragEnabled = false;
65    }
66
67    private void handleTouchEvent(MotionEvent ev) {
68        final int action = ev.getAction();
69        switch (action & MotionEvent.ACTION_MASK) {
70            case MotionEvent.ACTION_DOWN:
71                cancelDragging();
72                mIsDragEnabled = true;
73                break;
74            case MotionEvent.ACTION_MOVE:
75                if (mTouchState != TOUCH_STATE_SCROLLING && !mIsDragging && mIsDragEnabled) {
76                    determineDraggingStart(ev);
77                }
78                break;
79        }
80    }
81
82    @Override
83    public boolean onInterceptTouchEvent(MotionEvent ev) {
84        handleTouchEvent(ev);
85        return super.onInterceptTouchEvent(ev);
86    }
87
88    @Override
89    public boolean onTouchEvent(MotionEvent ev) {
90        handleTouchEvent(ev);
91        return super.onTouchEvent(ev);
92    }
93
94    public void trimMemory() {
95        mLastTouchedItem = null;
96    }
97
98    @Override
99    public boolean onTouch(View v, MotionEvent event) {
100        mLastTouchedItem = v;
101        mIsDragEnabled = true;
102        return false;
103    }
104
105    @Override
106    public boolean onLongClick(View v) {
107        // Return early if this is not initiated from a touch
108        if (!v.isInTouchMode()) return false;
109        // Return early if we are still animating the pages
110        if (mNextPage != INVALID_PAGE) return false;
111        // When we have exited all apps or are in transition, disregard long clicks
112        if (!mLauncher.isAllAppsVisible() ||
113                mLauncher.getWorkspace().isSwitchingState()) return false;
114        // Return if global dragging is not enabled
115        if (!mLauncher.isDraggingEnabled()) return false;
116
117        return beginDragging(v);
118    }
119
120    /*
121     * Determines if we should change the touch state to start scrolling after the
122     * user moves their touch point too far.
123     */
124    protected void determineScrollingStart(MotionEvent ev) {
125        if (!mIsDragging) super.determineScrollingStart(ev);
126    }
127
128    /*
129     * Determines if we should change the touch state to start dragging after the
130     * user moves their touch point far enough.
131     */
132    protected void determineDraggingStart(MotionEvent ev) {
133        /*
134         * Locally do absolute value. mLastMotionX is set to the y value
135         * of the down event.
136         */
137        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
138        final float x = ev.getX(pointerIndex);
139        final float y = ev.getY(pointerIndex);
140        final int xDiff = (int) Math.abs(x - mLastMotionX);
141        final int yDiff = (int) Math.abs(y - mLastMotionY);
142
143        final int touchSlop = mTouchSlop;
144        boolean yMoved = yDiff > touchSlop;
145        boolean isUpwardMotion = (yDiff / (float) xDiff) > mDragSlopeThreshold;
146
147        if (isUpwardMotion && yMoved && mLastTouchedItem != null) {
148            // Drag if the user moved far enough along the Y axis
149            beginDragging(mLastTouchedItem);
150
151            // Cancel any pending long press
152            if (mAllowLongPress) {
153                mAllowLongPress = false;
154                // Try canceling the long press. It could also have been scheduled
155                // by a distant descendant, so use the mAllowLongPress flag to block
156                // everything
157                final View currentPage = getPageAt(mCurrentPage);
158                if (currentPage != null) {
159                    currentPage.cancelLongPress();
160                }
161            }
162        }
163    }
164
165    public void setDragSlopeThreshold(float dragSlopeThreshold) {
166        mDragSlopeThreshold = dragSlopeThreshold;
167    }
168
169    @Override
170    protected void onDetachedFromWindow() {
171        cancelDragging();
172        super.onDetachedFromWindow();
173    }
174}
175