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      1 /*
      2  * Copyright (C) 2016 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 package com.android.launcher3.util;
     17 
     18 import android.graphics.Rect;
     19 import android.graphics.RectF;
     20 import android.view.MotionEvent;
     21 import android.view.TouchDelegate;
     22 import android.view.View;
     23 
     24 /**
     25  * This class differs from the framework {@link TouchDelegate} in that it transforms the
     26  * coordinates of the motion event to the provided bounds.
     27  *
     28  * You can also modify the bounds post construction. Since the bounds are available during layout,
     29  * this avoids new object creation during every layout.
     30  */
     31 public class TransformingTouchDelegate extends TouchDelegate {
     32     private static final Rect sTempRect = new Rect();
     33 
     34     private final RectF mBounds;
     35 
     36     private final RectF mTouchCheckBounds;
     37     private float mTouchExtension;
     38     private boolean mWasTouchOutsideBounds;
     39 
     40     private View mDelegateView;
     41     private boolean mDelegateTargeted;
     42 
     43     public TransformingTouchDelegate(View delegateView) {
     44         super(sTempRect, delegateView);
     45 
     46         mDelegateView = delegateView;
     47         mBounds = new RectF();
     48         mTouchCheckBounds = new RectF();
     49     }
     50 
     51     public void setBounds(int left, int top, int right, int bottom) {
     52         mBounds.set(left, top, right, bottom);
     53         updateTouchBounds();
     54     }
     55 
     56     public void extendTouchBounds(float extension) {
     57         mTouchExtension = extension;
     58         updateTouchBounds();
     59     }
     60 
     61     private void updateTouchBounds() {
     62         mTouchCheckBounds.set(mBounds);
     63         mTouchCheckBounds.inset(-mTouchExtension, -mTouchExtension);
     64     }
     65 
     66     public void setDelegateView(View view) {
     67         mDelegateView = view;
     68     }
     69 
     70     /**
     71      * Will forward touch events to the delegate view if the event is within the bounds
     72      * specified in the constructor.
     73      *
     74      * @param event The touch event to forward
     75      * @return True if the event was forwarded to the delegate, false otherwise.
     76      */
     77     public boolean onTouchEvent(MotionEvent event) {
     78         boolean sendToDelegate = false;
     79         switch (event.getAction()) {
     80             case MotionEvent.ACTION_DOWN:
     81                 mDelegateTargeted = mTouchCheckBounds.contains(event.getX(), event.getY());
     82                 if (mDelegateTargeted) {
     83                     mWasTouchOutsideBounds = !mBounds.contains(event.getX(), event.getY());
     84                     sendToDelegate = true;
     85                 }
     86                 break;
     87             case MotionEvent.ACTION_MOVE:
     88                 sendToDelegate = mDelegateTargeted;
     89                 break;
     90             case MotionEvent.ACTION_UP:
     91             case MotionEvent.ACTION_CANCEL:
     92                 sendToDelegate = mDelegateTargeted;
     93                 mDelegateTargeted = false;
     94                 break;
     95         }
     96         boolean handled = false;
     97         if (sendToDelegate) {
     98             float x = event.getX();
     99             float y = event.getY();
    100             if (mWasTouchOutsideBounds) {
    101                 event.setLocation(mBounds.centerX(), mBounds.centerY());
    102             } else {
    103                 event.offsetLocation(-mBounds.left, -mBounds.top);
    104             }
    105             handled = mDelegateView.dispatchTouchEvent(event);
    106             event.setLocation(x, y);
    107         }
    108         return handled;
    109     }
    110 }
    111