PagedViewWithDraggableItems.java revision 72b079e4031f42729056e999c20bf87281798eb9 
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.launcher2;
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 float mDragSlopeThreshold;
39
40    public PagedViewWithDraggableItems(Context context) {
41        super(context, null);
42    }
43
44    public PagedViewWithDraggableItems(Context context, AttributeSet attrs) {
45        super(context, attrs, 0);
46    }
47
48    public PagedViewWithDraggableItems(Context context, AttributeSet attrs, int defStyle) {
49        super(context, attrs, defStyle);
50    }
51
52    protected boolean beginDragging(View v) {
53        mIsDragging = true;
54        return false;
55    }
56
57    @Override
58    public boolean onInterceptTouchEvent(MotionEvent ev) {
59        final int action = ev.getAction();
60        switch (action & MotionEvent.ACTION_MASK) {
61            case MotionEvent.ACTION_DOWN:
62                mIsDragging = false;
63                mLastTouchedItem = null;
64                break;
65            case MotionEvent.ACTION_MOVE:
66                if (mTouchState != TOUCH_STATE_SCROLLING && !mIsDragging) {
67                    determineDraggingStart(ev);
68                }
69                break;
70        }
71        return super.onInterceptTouchEvent(ev);
72    }
73
74    @Override
75    public boolean onTouch(View v, MotionEvent event) {
76        mLastTouchedItem = v;
77        return false;
78    }
79
80    @Override
81    public boolean onTouchEvent(MotionEvent ev) {
82        final int action = ev.getAction();
83        switch (action & MotionEvent.ACTION_MASK) {
84            case MotionEvent.ACTION_DOWN:
85                mIsDragging = false;
86                mLastTouchedItem = null;
87                break;
88            case MotionEvent.ACTION_MOVE:
89                if (mTouchState != TOUCH_STATE_SCROLLING && !mIsDragging) {
90                    determineDraggingStart(ev);
91                }
92                break;
93        }
94        return super.onTouchEvent(ev);
95    }
96
97    @Override
98    public boolean onLongClick(View v) {
99        // Return early if this is not initiated from a touch
100        if (!v.isInTouchMode()) return false;
101        // Return early if we are still animating the pages
102        if (mNextPage != INVALID_PAGE) return false;
103        return beginDragging(v);
104    }
105
106
107    /*
108     * Determines if we should change the touch state to start scrolling after the
109     * user moves their touch point too far.
110     */
111    protected void determineScrollingStart(MotionEvent ev) {
112        if (!mIsDragging) super.determineScrollingStart(ev);
113    }
114
115    /*
116     * Determines if we should change the touch state to start dragging after the
117     * user moves their touch point far enough.
118     */
119    protected void determineDraggingStart(MotionEvent ev) {
120        /*
121         * Locally do absolute value. mLastMotionX is set to the y value
122         * of the down event.
123         */
124        final int pointerIndex = ev.findPointerIndex(mActivePointerId);
125        final float x = ev.getX(pointerIndex);
126        final float y = ev.getY(pointerIndex);
127        final int xDiff = (int) Math.abs(x - mLastMotionX);
128        final int yDiff = (int) Math.abs(y - mLastMotionY);
129
130        final int touchSlop = mTouchSlop;
131        boolean yMoved = yDiff > touchSlop;
132        boolean isUpwardMotion = (yDiff / (float) xDiff) > mDragSlopeThreshold;
133
134        if (isUpwardMotion && yMoved && mLastTouchedItem != null) {
135            // Drag if the user moved far enough along the Y axis
136            beginDragging(mLastTouchedItem);
137
138            // Cancel any pending long press
139            if (mAllowLongPress) {
140                mAllowLongPress = false;
141                // Try canceling the long press. It could also have been scheduled
142                // by a distant descendant, so use the mAllowLongPress flag to block
143                // everything
144                final View currentPage = getPageAt(mCurrentPage);
145                if (currentPage != null) {
146                    currentPage.cancelLongPress();
147                }
148            }
149        }
150    }
151
152    public void setDragSlopeThreshold(float dragSlopeThreshold) {
153        mDragSlopeThreshold = dragSlopeThreshold;
154    }
155}
156