ImageView依据手势进行缩放,拖动



package com.example.scale;

import android.content.Context;
import android.graphics.Matrix;
import android.graphics.PointF;
import android.util.AttributeSet;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.widget.ImageView;

/**
 * @author wuxif_000   ImageView依据手势进行缩放,拖动........
 *
 */
public class TouchImageView extends ImageView {
 Matrix matrix = new Matrix();
    Matrix savedMatrix = new Matrix();

    static final int NONE = 0;
    /**
     * 对imageView进行上、下、左、右拖动..........
     */
    static final int DRAG = 1;
    /**
     * 对imageView进行缩放...........
     */
    static final int ZOOM = 2;
    int mode = NONE;

    /**
     * MotionEvent.ACTION_DOWN的坐标
     */
    PointF start = new PointF();
    /**
     * 第一次感觉到两点的时候，获取两点间的中点坐标，以此点进行缩放，假设是多点触控的话........
     */
    PointF mid = new PointF();
    /**
     * 第一次感觉到两点的时候。两点间的距离
     */
    float oldDistance = 1f;
    /**
     * 对图片进行缩放的最大比例
     */
    private  final int  maxScale=5;

 public TouchImageView(Context context, AttributeSet attrs) {
  super(context, attrs);
 }
 @Override
 public boolean onTouchEvent(MotionEvent event) {
  switch (event.getAction() & MotionEvent.ACTION_MASK) {
  case MotionEvent.ACTION_DOWN:
   //第一个手指down的时候
    matrix.set(getImageMatrix());
             savedMatrix.set(matrix);
             start.set(event.getX(), event.getY());
             mode = DRAG;
   break;
  case MotionEvent.ACTION_POINTER_DOWN:
   //第二个手指down时。两点间的距离.......
   oldDistance=spacing(event);
    if (oldDistance > 10f) {
     matrix.set(savedMatrix);
                 //保存两点间的中点........
                 midPoint(mid, event);
                 //对图片进行缩放
                 mode = ZOOM;
         }
   break;
  case MotionEvent.ACTION_MOVE:
   if(mode==DRAG){
     matrix.set(savedMatrix);
    //一个手指进行上、下、左、右拖动...........
    //x,y移动的距离计算...........
     matrix.postTranslate(event.getX() - start.x, event.getY()
                         - start.y);
   }else if(mode==ZOOM){
    //对imageView进行缩放........
    //两点之间的距离
    float newDistance = spacing(event);
    //假设两点间的距离>10就进行缩放..........
    if (newDistance > 10f) {
      matrix.set(savedMatrix);
      //缩放最大为5
                    float f = newDistance / oldDistance;
     float scale = f>maxScale?maxScale:f;
                    //在最初两点间的中点，以该点进行缩放........
                    matrix.postScale(scale, scale, mid.x, mid.y);
            }
   }
   break;
  case MotionEvent.ACTION_UP:
   mode=NONE;
   //点击事件处理，旋转180度............
   if (Math.abs(event.getX()-start.x) < 10 & Math.abs(event.getY()-start.y) < 10) {
    matrix.set(savedMatrix);
    matrix.postRotate(180, getWidth()/2, getHeight()/2);
   }
   break;
  case MotionEvent.ACTION_POINTER_UP:
   mode=NONE;
   break;
  default:
   break;
  }
  setScaleType(ImageView.ScaleType.MATRIX);
  setImageMatrix(matrix);
  //return super.onTouchEvent(event);
  //要设为true,不然setImageMatrix(matrix)不起作用
  //要设为true,不然setImageMatrix(matrix)不起作用
  //要设为true,不然setImageMatrix(matrix)不起作用
  return true;
 }
 /**
  * 两点的距离 Determine the space between the first two fingers
  */
 private float spacing(MotionEvent event) {
  float x = event.getX(0) - event.getX(1);
  float y = event.getY(0) - event.getY(1);
  return FloatMath.sqrt(x * x + y * y);
 }

 /**
  * 两点的中点 Calculate the mid point of the first two fingers
  * */
 private void midPoint(PointF point, MotionEvent event) {
  //1,2的中点是(1+2) /2=1.5
  float x = event.getX(0) + event.getX(1);
  float y = event.getY(0) + event.getY(1);
  point.set(x / 2, y / 2);
 }

}