The Android Open Source Project | 9066cfe | 2009-03-03 19:31:44 -0800 | [diff] [blame] | 1 | /* |
| 2 | * Copyright (C) 2008 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 | |
| 17 | package android.view; |
| 18 | |
| 19 | import android.graphics.Rect; |
| 20 | import android.view.MotionEvent; |
| 21 | import android.view.View; |
| 22 | import android.view.ViewConfiguration; |
| 23 | |
| 24 | /** |
| 25 | * Helper class to handle situations where you want a view to have a larger touch area than its |
| 26 | * actual view bounds. The view whose touch area is changed is called the delegate view. This |
| 27 | * class should be used by an ancestor of the delegate. To use a TouchDelegate, first create an |
| 28 | * instance that specifies the bounds that should be mapped to the delegate and the delegate |
| 29 | * view itself. |
| 30 | * <p> |
| 31 | * The ancestor should then forward all of its touch events received in its |
| 32 | * {@link android.view.View#onTouchEvent(MotionEvent)} to {@link #onTouchEvent(MotionEvent)}. |
| 33 | * </p> |
| 34 | */ |
| 35 | public class TouchDelegate { |
| 36 | |
| 37 | /** |
| 38 | * View that should receive forwarded touch events |
| 39 | */ |
| 40 | private View mDelegateView; |
| 41 | |
| 42 | /** |
| 43 | * Bounds in local coordinates of the containing view that should be mapped to the delegate |
| 44 | * view. This rect is used for initial hit testing. |
| 45 | */ |
| 46 | private Rect mBounds; |
| 47 | |
| 48 | /** |
| 49 | * mBounds inflated to include some slop. This rect is to track whether the motion events |
| 50 | * should be considered to be be within the delegate view. |
| 51 | */ |
| 52 | private Rect mSlopBounds; |
| 53 | |
| 54 | /** |
| 55 | * True if the delegate had been targeted on a down event (intersected mBounds). |
| 56 | */ |
| 57 | private boolean mDelegateTargeted; |
| 58 | |
| 59 | /** |
| 60 | * The touchable region of the View extends above its actual extent. |
| 61 | */ |
| 62 | public static final int ABOVE = 1; |
| 63 | |
| 64 | /** |
| 65 | * The touchable region of the View extends below its actual extent. |
| 66 | */ |
| 67 | public static final int BELOW = 2; |
| 68 | |
| 69 | /** |
| 70 | * The touchable region of the View extends to the left of its |
| 71 | * actual extent. |
| 72 | */ |
| 73 | public static final int TO_LEFT = 4; |
| 74 | |
| 75 | /** |
| 76 | * The touchable region of the View extends to the right of its |
| 77 | * actual extent. |
| 78 | */ |
| 79 | public static final int TO_RIGHT = 8; |
| 80 | |
| 81 | private int mSlop; |
| 82 | |
| 83 | /** |
| 84 | * Constructor |
| 85 | * |
| 86 | * @param bounds Bounds in local coordinates of the containing view that should be mapped to |
| 87 | * the delegate view |
| 88 | * @param delegateView The view that should receive motion events |
| 89 | */ |
| 90 | public TouchDelegate(Rect bounds, View delegateView) { |
| 91 | mBounds = bounds; |
| 92 | |
| 93 | mSlop = ViewConfiguration.get(delegateView.getContext()).getScaledTouchSlop(); |
| 94 | mSlopBounds = new Rect(bounds); |
| 95 | mSlopBounds.inset(-mSlop, -mSlop); |
| 96 | mDelegateView = delegateView; |
| 97 | } |
| 98 | |
| 99 | /** |
| 100 | * Will forward touch events to the delegate view if the event is within the bounds |
| 101 | * specified in the constructor. |
| 102 | * |
| 103 | * @param event The touch event to forward |
| 104 | * @return True if the event was forwarded to the delegate, false otherwise. |
| 105 | */ |
| 106 | public boolean onTouchEvent(MotionEvent event) { |
| 107 | int x = (int)event.getX(); |
| 108 | int y = (int)event.getY(); |
| 109 | boolean sendToDelegate = false; |
| 110 | boolean hit = true; |
| 111 | boolean handled = false; |
| 112 | |
| 113 | switch (event.getAction()) { |
| 114 | case MotionEvent.ACTION_DOWN: |
| 115 | Rect bounds = mBounds; |
| 116 | |
| 117 | if (bounds.contains(x, y)) { |
| 118 | mDelegateTargeted = true; |
| 119 | sendToDelegate = true; |
| 120 | } |
| 121 | break; |
| 122 | case MotionEvent.ACTION_UP: |
| 123 | case MotionEvent.ACTION_MOVE: |
| 124 | sendToDelegate = mDelegateTargeted; |
| 125 | if (sendToDelegate) { |
| 126 | Rect slopBounds = mSlopBounds; |
| 127 | if (!slopBounds.contains(x, y)) { |
| 128 | hit = false; |
| 129 | } |
| 130 | } |
| 131 | break; |
| 132 | case MotionEvent.ACTION_CANCEL: |
| 133 | sendToDelegate = mDelegateTargeted; |
| 134 | mDelegateTargeted = false; |
| 135 | break; |
| 136 | } |
| 137 | if (sendToDelegate) { |
| 138 | final View delegateView = mDelegateView; |
| 139 | |
| 140 | if (hit) { |
| 141 | // Offset event coordinates to be inside the target view |
| 142 | event.setLocation(delegateView.getWidth() / 2, delegateView.getHeight() / 2); |
| 143 | } else { |
| 144 | // Offset event coordinates to be outside the target view (in case it does |
| 145 | // something like tracking pressed state) |
| 146 | int slop = mSlop; |
| 147 | event.setLocation(-(slop * 2), -(slop * 2)); |
| 148 | } |
| 149 | handled = delegateView.dispatchTouchEvent(event); |
| 150 | } |
| 151 | return handled; |
| 152 | } |
| 153 | } |