android 自定义ImageView实现图片缩放边界回弹和缩小回弹

<activity
android:name=".MainActivity"
android:label="@string/app_name"
android:theme="@android:style/Theme.Black.NoTitleBar.Fullscreen"  >
<intent-filter>
<action android:name="android.intent.action.MAIN" />

<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>

XML布局文件
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<LinearLayout
android:orientation="vertical"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/ll_viewArea">
</LinearLayout>

</RelativeLayout>

自定义容器
package com.example.ichimatsuou.zoomimage;

import android.app.Activity;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.util.DisplayMetrics;
import android.widget.FrameLayout;

public class ViewArea extends FrameLayout {  //前面说了ViewArea是一个布局， 所以这里当然要继承一个布局了。LinearLayout也可以
private int imgDisplayW;
private int imgDisplayH;
private int imgW;
private int imgH;
private ZoomImageView touchView;
private DisplayMetrics dm;
//resId为图片资源id
public ViewArea(Context context,int resId) { //第二个参数是图片的资源ID，当然也可以用别的方式获取图片
/*        dm = new DisplayMetrics();
((Activity)context).getWindowManager().getDefaultDisplay().getMetrics(dm);
imgDisplayW = dm.widthPixels;
imgDisplayH = dm.heightPixels;*///这种方式获取的屏幕大小和下面的方式结果是一样的，都是480x800（i9000分辨率）
super(context);
imgDisplayW = ((Activity)context).getWindowManager().getDefaultDisplay().getWidth();//这里的宽高要和xml中的LinearLayout大小一致，如果要指定大小。xml中 LinearLayout的宽高一定要用px像素单位，因为这里的宽高是像素，用dp会有误差！
imgDisplayH = ((Activity)context).getWindowManager().getDefaultDisplay().getHeight();

touchView = new ZoomImageView(context,imgDisplayW,imgDisplayH);//这句就是我们的自定义ImageView
touchView.setImageResource(resId);//给我们的自定义imageView设置要显示的图片
Bitmap img = BitmapFactory.decodeResource(context.getResources(), resId);
imgW = img.getWidth();
imgH = img.getHeight();
//图片第一次加载进来，判断图片大小从而确定第一次图片的显示方式。
int layout_w = imgW>imgDisplayW?imgDisplayW:imgW;
int layout_h = imgH>imgDisplayH?imgDisplayH:imgH;

//下面的代码是判断图片初始显示样式的，当然可以根据你的想法随意显示，我这里是将宽大于高的图片按照宽缩小的比例把高压缩，前提必须是宽度超出了屏幕大小，相反，如果高大于宽，我将图片按照高缩小的比例把宽压缩，前提必须是高度超出了屏幕大小
if(imgW>=imgH) {
if(layout_w==imgDisplayW){
layout_h = (int) (imgH*((float)imgDisplayW/imgW));
}
}else {
if(layout_h==imgDisplayH){
layout_w = (int) (imgW*((float)imgDisplayH/imgH));
}
}
//这里需要注意的是，采用FreamLayout或者LinearLayout的好处是，如果压缩后的图片扔有一个边大于屏幕，那么只显示在屏幕内的部分，可以通过移动后看见外部（不会裁剪掉图片），如果采用RelativeLayout布局，图片会始终完整显示在屏幕内部，不会有超出屏幕的现象。如果图片不是完全占满屏幕，那么在屏幕上没有图片的地方拖动，图片也会移动，这样的体验不太好，建议用FreamLayout或者LinearLayout。
touchView.setLayoutParams(new FrameLayout.LayoutParams(layout_w,layout_h));//这是自定义imageView的大小，也就是触摸范围
this.addView(touchView);
}

}

<pre name="code" class="java">/**
* ACTION_DOWN is for the first finger that touches the screen. This starts the gesture. The pointer data for this finger is always at index 0 in the MotionEvent.
* ACTION_POINTER_DOWN is for extra fingers that enter the screen beyond the first. The pointer data for this finger is at the index returned by getActionIndex().
* ACTION_POINTER_UP is sent when a finger leaves the screen but at least one finger is still touching it. The last data sample about the finger that went up is at the index returned by getActionIndex().
* ACTION_UP is sent when the last finger leaves the screen. The last data sample about the finger that went up is at index 0. This ends the gesture.
* ACTION_CANCEL means the entire gesture was aborted for some reason. This ends the gesture.
*/

自定义ImageView
package com.example.ichimatsuou.zoomimage;

import android.content.Context;
import android.util.FloatMath;
import android.view.MotionEvent;
import android.view.animation.TranslateAnimation;
import android.widget.ImageView;

public class ZoomImageView extends ImageView {

static final int NONE = 0;//表示当前没有状态
static final int DRAG = 1;     //表示当前处于移动状态
static final int ZOOM = 2;     //表示当前处于缩放状态
static final int BIGGER = 3;   //表示放大图片
static final int SMALLER = 4;  //表示缩小图片
private int mode = NONE;      //mode用于标示当前处于什么状态

private float beforeLenght;  //第一次触摸两点的距离
private float afterLenght;    //移动后两点的距离
private float scale = 0.04f;  //缩放因子

private int screenW;//下面两句图片的移动范围，及ViewArea的范围，也就是linearLayout的范围，也就是屏幕方位（都是填满父控件属性）
private int screenH;

private int start_x;//开始触摸点
private int start_y;
private int stop_x ;//结束触摸点
private int stop_y ;
private TranslateAnimation trans; //回弹动画

public ZoomImageView(Context context,int w,int h)//这里传进来的w，h就是图片的移动范围
{
super(context);
this.setPadding(0, 0, 0, 0);
screenW = w;
screenH = h;
}
//用来计算2个触摸点的距离
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);
}

@Override
public boolean onTouchEvent(MotionEvent event)
{
switch (event.getAction() & MotionEvent.ACTION_MASK) {//MotionEvent.ACTION_MASK表示多点触控事件
case MotionEvent.ACTION_DOWN:
mode = DRAG;
stop_x = (int) event.getRawX();//表示相对于屏幕左上角为原点的坐标
stop_y = (int) event.getRawY();//同上
start_x = stop_x - this.getLeft();//用(int) event.getX();一样,表示相对于当前点击Widget（控件）左上角的坐标，这里就是相对于自定义imageView左上角的坐标.建议用前者，如果不是全屏拖动，而是指定范围内，一样适用！
start_y = stop_y - this.getTop();////用(int) event.getY();一样,this.getTop()表示其顶部相对于父控件的距离

if(event.getPointerCount()==2)
beforeLenght = spacing(event);
break;
case MotionEvent.ACTION_POINTER_DOWN:
if (spacing(event) > 10f) {
mode = ZOOM;
beforeLenght = spacing(event);
}
break;
case MotionEvent.ACTION_UP:

int disX = 0;
int disY = 0;
if(getHeight()<=
4000
screenH )//
{
if(this.getTop()<0 )
{
disY = getTop();
//layout(left , top, right,bottom)函数表示设置view的位置。
this.layout(this.getLeft(), 0, this.getRight(), 0 + this.getHeight());

}
else if(this.getBottom()>=screenH)
{
disY = getHeight()- screenH+getTop();
this.layout(this.getLeft(), screenH-getHeight(), this.getRight(), screenH);
}
}else{
int Y1 = getTop();
int Y2 = getHeight()- screenH+getTop();
if(Y1>0)
{
disY= Y1;
this.layout(this.getLeft(), 0, this.getRight(), 0 + this.getHeight());
}else if(Y2<0){
disY = Y2;
this.layout(this.getLeft(), screenH-getHeight(), this.getRight(), screenH);
}
}
if(getWidth()<=screenW)
{
if(this.getLeft()<0)
{
disX = getLeft();
this.layout(0, this.getTop(), 0+getWidth(), this.getBottom());
}
else if(this.getRight()>screenW)
{
disX = getWidth()-screenW+getLeft();
this.layout(screenW-getWidth(), this.getTop(), screenW, this.getBottom());
}
}else {
int X1 = getLeft();
int X2 = getWidth()-screenW+getLeft();
if(X1>0) {
disX = X1;
this.layout(0, this.getTop(), 0+getWidth(), this.getBottom());
}else if(X2<0) {
disX = X2;
this.layout(screenW-getWidth(), this.getTop(), screenW, this.getBottom());
}

}
//如果图片缩放到宽小于屏幕的宽，那么自动放大.
while(getWidth()<screenW) {

setScale(scale,BIGGER);
}
//根据disX和disY的偏移量采用移动动画回弹归位，动画时间为500毫秒。
if(disX!=0 || disY!=0)
{
trans = new TranslateAnimation(disX, 0, disY, 0);
trans.setDuration(500);
this.startAnimation(trans);
}
mode = NONE;
break;
case MotionEvent.ACTION_POINTER_UP:
mode = NONE;
break;
case MotionEvent.ACTION_MOVE:

if (mode == DRAG) {
//执行拖动事件的时，不断变换自定义imageView的位置从而达到拖动效果
this.setPosition(stop_x - start_x, stop_y - start_y, stop_x + this.getWidth() - start_x, stop_y - start_y + this.getHeight());
stop_x = (int) event.getRawX();
stop_y = (int) event.getRawY();

} else if (mode == ZOOM) {
if(spacing(event)>10f)
{
afterLenght = spacing(event);
float gapLenght = afterLenght - beforeLenght;
if(gapLenght == 0) {
break;
}
//图片宽度（也就是自定义imageView）必须大于70才可以缩放
else if(Math.abs(gapLenght)>5f&&getWidth()>70)
{
if(gapLenght>0) {
this.setScale(scale,BIGGER);
}else {
this.setScale(scale,SMALLER);
}
beforeLenght = afterLenght; //这句不能少。
}
}
}
break;
}
return true;
}

private void setScale(float temp,int flag) {

if(flag==BIGGER) {
//setFrame(left , top, right,bottom)函数表示改变当前view的框架，也就是大小。
this.setFrame(this.getLeft()-(int)(temp*this.getWidth()),
this.getTop()-(int)(temp*this.getHeight()),
this.getRight()+(int)(temp*this.getWidth()),
this.getBottom()+(int)(temp*this.getHeight()));
}else if(flag==SMALLER){
this.setFrame(this.getLeft()+(int)(temp*this.getWidth()),
this.getTop()+(int)(temp*this.getHeight()),
this.getRight()-(int)(temp*this.getWidth()),
this.getBottom()-(int)(temp*this.getHeight()));
}
}

private void setPosition(int left,int top,int right,int bottom) {
this.layout(left,top,right,bottom);
}
}

package com.example.ichimatsuou.zoomimage;

import android.app.Activity;
import android.os.Bundle;
import android.widget.LinearLayout;

public class MainActivity extends Activity {

private LinearLayout ll_viewArea;
private LinearLayout.LayoutParams parm;
private ViewArea viewArea;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

ll_viewArea = (LinearLayout) findViewById(R.id.ll_viewArea);
parm = new LinearLayout.LayoutParams(LinearLayout.LayoutParams.MATCH_PARENT, LinearLayout.LayoutParams.MATCH_PARENT);
viewArea = new ViewArea(MainActivity.this,R.drawable.thumb1);    //自定义布局控件，用来初始化并存放自定义imageView
ll_viewArea.addView(viewArea,parm);

}
}