android手势缩放imageview,Android 重载ImageView 可以使用手势放大缩小拖动

一 JAVA

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;

// by ikmb@163.com

public class ImageTouchView extends ImageView {

private PointF startPoint = new PointF();

private Matrix matrix = new Matrix();

private Matrix currentMaritx = new Matrix();

private int mode = 0;//用于标记模式

private static final int DRAG = 1;//拖动

private static final int ZOOM = 2;//放大

private float startDis = 0;

private PointF midPoint;//中心点

/**

* 默认构造函数

* @param context

*/

public ImageTouchView(Context context){

super(context);

}

/**

* 该构造方法在静态引入XML文件中是必须的

* @param context

* @param paramAttributeSet

*/

public ImageTouchView(Context context,AttributeSet paramAttributeSet){

super(context,paramAttributeSet);

}

public boolean onTouchEvent(MotionEvent event) {

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

case MotionEvent.ACTION_DOWN:

mode = DRAG;

currentMaritx.set(this.getImageMatrix());//记录ImageView当期的移动位置

startPoint.set(event.getX(),event.getY());//开始点

break;

case MotionEvent.ACTION_MOVE://移动事件

if (mode == DRAG) {//图片拖动事件

float dx = event.getX() - startPoint.x;//x轴移动距离

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

matrix.set(currentMaritx);//在当前的位置基础上移动

matrix.postTranslate(dx, dy);

} else if(mode == ZOOM){//图片放大事件

float endDis = distance(event);//结束距离

if(endDis > 10f){

float scale = endDis / startDis;//放大倍数

//Log.v("scale=", String.valueOf(scale));

matrix.set(currentMaritx);

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

}

}

break;

case MotionEvent.ACTION_UP:

mode = 0;

break;

//有手指离开屏幕，但屏幕还有触点(手指)

case MotionEvent.ACTION_POINTER_UP:

mode = 0;

break;

//当屏幕上已经有触点(手指),再有一个手指压下屏幕

case MotionEvent.ACTION_POINTER_DOWN:

mode = ZOOM;

startDis = distance(event);

if(startDis > 10f){//避免手指上有两个茧

midPoint = mid(event);

currentMaritx.set(this.getImageMatrix());//记录当前的缩放倍数

}

break;

}

this.setImageMatrix(matrix);

return true;

}

/**

* 两点之间的距离

* @param event

* @return

*/

private static float distance(MotionEvent event){

//两根线的距离

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

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

return FloatMath.sqrt(dx*dx + dy*dy);

}

/**

* 计算两点之间中心点的距离

* @param event

* @return

*/

private static PointF mid(MotionEvent event){

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

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

return new PointF(midx/2, midy/2);

}

}

二 xml

xmlns:tools="http://schemas.android.com/tools"

android:layout_width="fill_parent"

android:layout_height="fill_parent"

android:orientation="vertical" >

android:layout_width="fill_parent"

android:layout_height="wrap_content"

android:text="@string/hello_world"

tools:context=".MainActivity" />

android:layout_width="wrap_content"

android:layout_height="wrap_content"

android:src="@drawable/guide_0"

android:scaleType="matrix"

android:id="@+id/img"

/>

By ikmb@163.com