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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.util.FloatMath;
     21 import android.view.MotionEvent;
     22 import android.view.MotionEvent.PointerCoords;
     23 
     24 import com.android.gallery3d.common.ApiHelper;
     25 
     26 public final class MotionEventHelper {
     27     private MotionEventHelper() {}
     28 
     29     public static MotionEvent transformEvent(MotionEvent e, Matrix m) {
     30         // We try to use the new transform method if possible because it uses
     31         // less memory.
     32         if (ApiHelper.HAS_MOTION_EVENT_TRANSFORM) {
     33             return transformEventNew(e, m);
     34         } else {
     35             return transformEventOld(e, m);
     36         }
     37     }
     38 
     39     @TargetApi(ApiHelper.VERSION_CODES.HONEYCOMB)
     40     private static MotionEvent transformEventNew(MotionEvent e, Matrix m) {
     41         MotionEvent newEvent = MotionEvent.obtain(e);
     42         newEvent.transform(m);
     43         return newEvent;
     44     }
     45 
     46     // This is copied from Input.cpp in the android framework.
     47     private static MotionEvent transformEventOld(MotionEvent e, Matrix m) {
     48         long downTime = e.getDownTime();
     49         long eventTime = e.getEventTime();
     50         int action = e.getAction();
     51         int pointerCount = e.getPointerCount();
     52         int[] pointerIds = getPointerIds(e);
     53         PointerCoords[] pointerCoords = getPointerCoords(e);
     54         int metaState = e.getMetaState();
     55         float xPrecision = e.getXPrecision();
     56         float yPrecision = e.getYPrecision();
     57         int deviceId = e.getDeviceId();
     58         int edgeFlags = e.getEdgeFlags();
     59         int source = e.getSource();
     60         int flags = e.getFlags();
     61 
     62         // Copy the x and y coordinates into an array, map them, and copy back.
     63         float[] xy = new float[pointerCoords.length * 2];
     64         for (int i = 0; i < pointerCount;i++) {
     65             xy[2 * i] = pointerCoords[i].x;
     66             xy[2 * i + 1] = pointerCoords[i].y;
     67         }
     68         m.mapPoints(xy);
     69         for (int i = 0; i < pointerCount;i++) {
     70             pointerCoords[i].x = xy[2 * i];
     71             pointerCoords[i].y = xy[2 * i + 1];
     72             pointerCoords[i].orientation = transformAngle(
     73                 m, pointerCoords[i].orientation);
     74         }
     75 
     76         MotionEvent n = MotionEvent.obtain(downTime, eventTime, action,
     77                 pointerCount, pointerIds, pointerCoords, metaState, xPrecision,
     78                 yPrecision, deviceId, edgeFlags, source, flags);
     79 
     80         return n;
     81     }
     82 
     83     private static int[] getPointerIds(MotionEvent e) {
     84         int n = e.getPointerCount();
     85         int[] r = new int[n];
     86         for (int i = 0; i < n; i++) {
     87             r[i] = e.getPointerId(i);
     88         }
     89         return r;
     90     }
     91 
     92     private static PointerCoords[] getPointerCoords(MotionEvent e) {
     93         int n = e.getPointerCount();
     94         PointerCoords[] r = new PointerCoords[n];
     95         for (int i = 0; i < n; i++) {
     96             r[i] = new PointerCoords();
     97             e.getPointerCoords(i, r[i]);
     98         }
     99         return r;
    100     }
    101 
    102     private static float transformAngle(Matrix m, float angleRadians) {
    103         // Construct and transform a vector oriented at the specified clockwise
    104         // angle from vertical.  Coordinate system: down is increasing Y, right is
    105         // increasing X.
    106         float[] v = new float[2];
    107         v[0] = FloatMath.sin(angleRadians);
    108         v[1] = -FloatMath.cos(angleRadians);
    109         m.mapVectors(v);
    110 
    111         // Derive the transformed vector's clockwise angle from vertical.
    112         float result = (float) Math.atan2(v[0], -v[1]);
    113         if (result < -Math.PI / 2) {
    114             result += Math.PI;
    115         } else if (result > Math.PI / 2) {
    116             result -= Math.PI;
    117         }
    118         return result;
    119     }
    120 }
    121