前几天做项目用到相机拍照，之后能对图片进行缩放，拖拽，在此我将其单独抽取出来，后面用到时直接拿来用就行了！

效果图：

注：这里不仅能按钮缩放，还能多点触摸缩放和拖拽功能！

1.布局：

android:id="@+id/flayout_img_display"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

android:id="@+id/linearLayout_img_display"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:layout_gravity="center"

android:gravity="center" >

android:id="@+id/img_display"

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:paddingBottom="5.0dip"

android:paddingTop="5.0dip"

android:scaleType="matrix" />

android:id="@+id/relativeLayout1"

android:layout_width="fill_parent"

android:layout_height="wrap_content" >

android:id="@+id/btn_min"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_alignParentLeft="true"

android:enabled="false"

android:text="缩小" />

android:id="@+id/btn_out"

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:layout_alignParentBottom="true"

android:layout_alignParentRight="true"

android:text="放大" />

2.就一个类：

import android.app.Activity;

import android.content.Intent;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.graphics.Matrix;

import android.graphics.PointF;

import android.os.Bundle;

import android.util.FloatMath;

import android.util.Log;

import android.view.MotionEvent;

import android.view.View;

import android.view.View.OnClickListener;

import android.view.View.OnTouchListener;

import android.widget.Button;

import android.widget.FrameLayout;

import android.widget.ImageView;

import android.widget.LinearLayout;

/**

* 缩放图片界面

* @author ZHF

*

*/

public class MainActivity extends Activity {

public static final String TAG = "ImgDisplayActivity";

//控件声明

private Button btnZoomin, btnZoomout;

private ImageView imgDisPlay;

private LinearLayout lLayoutDisplay;

private FrameLayout fLayoutDisplay;

private Bitmap bitmap;

private int imgId = 0;

private double scale_in = 0.8;//缩小比例

private double scale_out = 1.25;//放大比例

private float scaleWidth = 1;

private float scaleHeight = 1;

//模式：0：什么都不干；1：拖拽； 2：缩放

public static final int NONE = 0;

public static final int DRAG = 1;

public static final int ZOOM = 2;

//声明触发的事件模式

private int mode = NONE;

private Matrix matrix; //矩阵

private Matrix currMatrix; //当前矩阵

private PointF starPoint;

private PointF midPoint;

private float startDistance;

@Override

protected void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_main);

//初始化

fLayoutDisplay = (FrameLayout) findViewById(R.id.flayout_img_display);

lLayoutDisplay = (LinearLayout) findViewById(R.id.linearLayout_img_display);

imgDisPlay = (ImageView) findViewById(R.id.img_display);

btnZoomin = (Button) findViewById(R.id.btn_min);

btnZoomout = (Button) findViewById(R.id.btn_out);

matrix = new Matrix(); //保存拖拽变化

currMatrix = new Matrix();// 当前的

starPoint = new PointF();//开始点的位置

btnZoomin.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

zoomIn();

}

});

btnZoomout.setOnClickListener(new OnClickListener() {

@Override

public void onClick(View v) {

zoomOut();//放大

}

});

imgDisPlay.setImageResource(R.drawable.img);

//给图片绑定监听器哦

imgDisPlay.setOnTouchListener(new ImageViewOnTouchListener());

}

/**放大操作**/

private void zoomOut() {

reSizeBmp(scale_out);

btnZoomin.setEnabled(true);

}

/**缩小操作**/

private void zoomIn() {

reSizeBmp(scale_in);

}

/**接收传入的缩放比例实现缩放**/

private void reSizeBmp(double scale) {

//缩放比例

scaleWidth = (float) (scaleWidth * scale);

scaleHeight = (float) (scaleHeight * scale);

Matrix matrix = new Matrix();

matrix.postScale(scaleWidth, scaleHeight); //设计缩放比例

imgDisPlay.setImageMatrix(matrix);

}

/**计算触摸实现缩放**/

final class ImageViewOnTouchListener implements OnTouchListener{

@Override

public boolean onTouch(View v, MotionEvent event) {

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

case MotionEvent.ACTION_DOWN: //一只手指按下

Log.i(TAG,"一只手指按下");

currMatrix.set(matrix);

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

mode = DRAG;

break;

case MotionEvent.ACTION_POINTER_DOWN: //如果有一只手指按下屏幕，后续又有一个手指按下 // 两只手指按下

Log.i(TAG,"又有一只手指按下");

startDistance = distance(event);//记下两点的距离

Log.i(TAG, startDistance+"");

if(startDistance > 5f) { //两个手指之间的最小距离像素大于5，认为是多点触摸

mode = ZOOM;

currMatrix.set(matrix);

midPoint = getMidPoint(event); //记下两个点之间的中心点

}

break;

case MotionEvent.ACTION_MOVE:

if(mode == DRAG) { //拖拽模式

Log.i(TAG,"一只手指在拖拽");

//开始--》结束点的距离

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

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

matrix.set(currMatrix);

matrix.postTranslate(dx, dy);//移动到指定点：矩阵移动比例；eg:缩放有缩放比例

} else if(mode == ZOOM) { //缩放模式

Log.i(TAG,"正在缩放");

float distance = distance(event); //两点之间的距离

if(distance > 5f) {

matrix.set(currMatrix);

float cale = distance / startDistance;

matrix.preScale(cale, cale, midPoint.x, midPoint.y); //进行比例缩放

}

}

break;

case MotionEvent.ACTION_UP: //最后一只手指离开屏幕后触发此事件

case MotionEvent.ACTION_POINTER_UP: //一只手指离开屏幕，但还有一只手指在上面会触此事件

//什么都没做

mode = NONE;

break;

default:

break;

}

imgDisPlay.setImageMatrix(matrix);

//两只手指的缩放

return true;

}

}

/**计算两点之间的距离像素**/

private float distance(MotionEvent e) {

float eX = e.getX(1) - e.getX(0); //后面的点坐标 - 前面点的坐标

float eY = e.getY(1) - e.getY(0);

return FloatMath.sqrt(eX * eX + eY * eY);

}

/**计算两点之间的中心点**/

private PointF getMidPoint(MotionEvent event) {

float x = (event.getX(1) - event.getX(0)) / 2;

float y = (event.getY(1) - event.getY(0)) / 2;

return new PointF(x,y);

}

}

ok！主要的算法就在ImageViewOnTouchListener监听器当中，要考虑那三种情况(缩放、拖拽、什么都不干)，另外需要注意的就是，单个手指和两个以上手指的情况。