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      1 /*
      2  * Copyright (C) 2012 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.gallery3d.util;
     17 
     18 import android.annotation.TargetApi;
     19 import android.graphics.Matrix;
     20 import android.view.MotionEvent;
     21 import android.view.MotionEvent.PointerCoords;
     22 
     23 import com.android.gallery3d.common.ApiHelper;
     24 
     25 public final class MotionEventHelper {
     26     private MotionEventHelper() {}
     27 
     28     public static MotionEvent transformEvent(MotionEvent e, Matrix m) {
     29         // We try to use the new transform method if possible because it uses
     30         // less memory.
     31         if (ApiHelper.HAS_MOTION_EVENT_TRANSFORM) {
     32             return transformEventNew(e, m);
     33         } else {
     34             return transformEventOld(e, m);
     35         }
     36     }
     37 
     38     @TargetApi(ApiHelper.VERSION_CODES.HONEYCOMB)
     39     private static MotionEvent transformEventNew(MotionEvent e, Matrix m) {
     40         MotionEvent newEvent = MotionEvent.obtain(e);
     41         newEvent.transform(m);
     42         return newEvent;
     43     }
     44 
     45     // This is copied from Input.cpp in the android framework.
     46     private static MotionEvent transformEventOld(MotionEvent e, Matrix m) {
     47         long downTime = e.getDownTime();
     48         long eventTime = e.getEventTime();
     49         int action = e.getAction();
     50         int pointerCount = e.getPointerCount();
     51         int[] pointerIds = getPointerIds(e);
     52         PointerCoords[] pointerCoords = getPointerCoords(e);
     53         int metaState = e.getMetaState();
     54         float xPrecision = e.getXPrecision();
     55         float yPrecision = e.getYPrecision();
     56         int deviceId = e.getDeviceId();
     57         int edgeFlags = e.getEdgeFlags();
     58         int source = e.getSource();
     59         int flags = e.getFlags();
     60 
     61         // Copy the x and y coordinates into an array, map them, and copy back.
     62         float[] xy = new float[pointerCoords.length * 2];
     63         for (int i = 0; i < pointerCount;i++) {
     64             xy[2 * i] = pointerCoords[i].x;
     65             xy[2 * i + 1] = pointerCoords[i].y;
     66         }
     67         m.mapPoints(xy);
     68         for (int i = 0; i < pointerCount;i++) {
     69             pointerCoords[i].x = xy[2 * i];
     70             pointerCoords[i].y = xy[2 * i + 1];
     71             pointerCoords[i].orientation = transformAngle(
     72                 m, pointerCoords[i].orientation);
     73         }
     74 
     75         MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
     76                 pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
     77                 yPrecision, deviceId, edgeFlags, source, flags);
     78 
     79         return n;
     80     }
     81 
     82     private static int[] getPointerIds(MotionEvent e) {
     83         int n = e.getPointerCount();
     84         int[] r = new int[n];
     85         for (int i = 0; i < n; i++) {
     86             r[i] = e.getPointerId(i);
     87         }
     88         return r;
     89     }
     90 
     91     private static PointerCoords[] getPointerCoords(MotionEvent e) {
     92         int n = e.getPointerCount();
     93         PointerCoords[] r = new PointerCoords[n];
     94         for (int i = 0; i < n; i++) {
     95             r[i] = new PointerCoords();
     96             e.getPointerCoords(i, r[i]);
     97         }
     98         return r;
     99     }
    100 
    101     private static float transformAngle(Matrix m, float angleRadians) {
    102         // Construct and transform a vector oriented at the specified clockwise
    103         // angle from vertical.  Coordinate system: down is increasing Y, right is
    104         // increasing X.
    105         float[] v = new float[2];
    106         v[0] = (float) Math.sin(angleRadians);
    107         v[1] = (float) -Math.cos(angleRadians);
    108         m.mapVectors(v);
    109 
    110         // Derive the transformed vector's clockwise angle from vertical.
    111         float result = (float) Math.atan2(v[0], -v[1]);
    112         if (result < -Math.PI / 2) {
    113             result += Math.PI;
    114         } else if (result > Math.PI / 2) {
    115             result -= Math.PI;
    116         }
    117         return result;
    118     }
    119 }
    120