android 多点触摸实现图片缩放

package com.touch;

import android.graphics.Matrix;

import android.graphics.PointF;

import android.util.FloatMath;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnTouchListener;

import android.widget.ImageView;

public class MulitPointTouchListener implements OnTouchListener {

Matrix matrix = new Matrix();

Matrix savedMatrix = new Matrix();

static final int NONE = 0;

static final int DRAG = 1;

static final int ZOOM = 2;

int mode = NONE;

PointF start = new PointF();

PointF mid = new PointF();

float oldDist = 1f;

@Override

public boolean onTouch(View v, MotionEvent event) {

ImageView view = (ImageView) v;

switch (event.getAction() & MotionEvent.ACTION_MASK) {

case MotionEvent.ACTION_DOWN:

matrix.set(view.getImageMatrix());

savedMatrix.set(matrix);

start.set(event.getX(), event.getY());

mode = DRAG;



break;

case MotionEvent.ACTION_POINTER_DOWN:

oldDist = spacing(event);

if (oldDist > 10f) {

savedMatrix.set(matrix);

midPoint(mid, event);

mode = ZOOM;

}

break;

case MotionEvent.ACTION_UP:

case MotionEvent.ACTION_POINTER_UP:

mode = NONE;

break;

case MotionEvent.ACTION_MOVE:

if (mode == DRAG) {

matrix.set(savedMatrix);

matrix.postTranslate(event.getX() - start.x, event.getY()

- start.y);

} else if (mode == ZOOM) {

float newDist = spacing(event);

if (newDist > 10f) {

matrix.set(savedMatrix);

float scale = newDist / oldDist;

matrix.postScale(scale, scale, mid.x, mid.y);

}

}

break;

}

view.setImageMatrix(matrix);

return true;

}





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);

}



private void midPoint(PointF point, MotionEvent event) {

float x = event.getX(0) + event.getX(1);

float y = event.getY(0) + event.getY(1);

point.set(x / 2, y / 2);

}

}

imageView.setOnTouchListener(new MulitPointTouchListener ());在xml中要将图片的缩放格式改成Matrix