android 图片任意拖拉,android中图片的拖拉和缩放

首先是布局文件，引入图片

activity

package cn.wonders.drag;

import android.support.v7.app.ActionBarActivity;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnTouchListener;

import android.widget.ImageView;

import android.graphics.Matrix;

import android.graphics.PointF;

import android.os.Bundle;

public class MainActivity extends ActionBarActivity {

private ImageView imageView;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

imageView = (ImageView) findViewById(R.id.imageView);

imageView.setOnTouchListener(new TonchListener());

}

private final class TonchListener implements OnTouchListener {

private PointF startPoint = new PointF();

private Matrix matrix = new Matrix();

//照片当前的移动位子

private Matrix currentMatrix = new Matrix();

//模式

private int mode = 0;

//拖拉

private final static int GRAG = 1;

//多点触摸

private final static int ZOOM = 2;

//开始时2根手指的距离

private float startDis;

//中间点

private PointF midPoint;

@Override

public boolean onTouch(View v, MotionEvent event) {

//取后8位

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

case MotionEvent.ACTION_DOWN:

//第一次按下时记录坐标

mode = GRAG;

currentMatrix.set(imageView.getImageMatrix());

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

break;

case MotionEvent.ACTION_MOVE:

if(mode == GRAG) {

float dx = event.getX() - startPoint.x;

float dy = event.getY() - startPoint.y;

//实现位子的移动,在上一次的基础上移动

matrix.set(currentMatrix);

matrix.postTranslate(dx, dy);

}else if (mode == ZOOM) {//缩放

float endDis = distance(event);

//得到缩放倍数

if(endDis > 10f) {

float scale = endDis/startDis;

//参数：x和y轴的放大倍数，以及中心点

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

}

}

break;

case MotionEvent.ACTION_UP:

break;

//在此前已经有手指按下，屏幕上至少有2根手指

case MotionEvent.ACTION_POINTER_DOWN:

mode = ZOOM;

startDis = distance(event);

//距离大于10个像素才处理，防止有手指分叉或有茧；

if(startDis > 10f) {

midPoint = mid(event);

//记录当前的放大倍数

currentMatrix.set(imageView.getImageMatrix());

}

break;

case MotionEvent.ACTION_POINTER_UP:

mode = 0;

break;

default:

break;

}

imageView.setImageMatrix(matrix);

//消费掉事件

return true;

}

}

//返回2个手指间的距离

private static float distance(MotionEvent event) {

float dx = event.getX(1) - event.getX(0);

float dy = event.getY(1) - event.getY(0);

return (float) Math.sqrt(dx*dx+dy*dy);

}

//计算中心点,为2根手指的中心点

private static PointF mid(MotionEvent event) {

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

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

return new PointF(dx/2, dy/2);

}

}