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