Android学习篇章10-Matrix图片放大缩小

public class MainActivity extends Activity {

ImageView  img1=null;
public static final  int NONE=0;
public static final  int DRAG=1;
public static final  int ZOOM=2;
public int state=NONE;
Matrix  matrix=new Matrix();
Matrix  m=new Matrix();
PointF   startPoint=null;
PointF   startPoint2=null;
float    startDist=0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
img1=(ImageView)findViewById(R.id.img1);
img1.setOnTouchListener(lst);
}

OnTouchListener  lst=new OnTouchListener() {
@Override
public boolean onTouch(View v, MotionEvent event) {
int action=event.getAction();
action=action&0x00ff;
switch(action)
{
//一根手指按下  拖拽
case MotionEvent.ACTION_DOWN:
//保存上一次移动结束后的状态矩阵
m.set(matrix);
startPoint=new PointF(event.getX(), event.getY());
state=DRAG;
break;
//2根手指头
case MotionEvent.ACTION_POINTER_DOWN:
state=ZOOM;
if(event.getPointerCount()==2)
{
//记录2根手指的起始位置
m.set(matrix);
startPoint=new PointF(event.getX(0),event.getY(0));
startPoint2=new PointF(event.getX(1),event.getY(1));
startDist=getDist(startPoint.x, startPoint.y,
startPoint2.x, startPoint2.y);
}
break;
case MotionEvent.ACTION_POINTER_UP:
if(event.getPointerCount()==1)
{
state=DRAG;
}
break;
case MotionEvent.ACTION_MOVE:
if(state==DRAG)
{
//处于拖动状态
float x= event.getX();
float y=event.getY();
float distX=x-startPoint.x;
float distY=y-startPoint.y;
//在每一次移动之前要先恢复原有状态矩阵
matrix.set(m);
matrix.postTranslate(distX, distY);
}else if(state==ZOOM)
{
//双点触摸 实现缩放  和旋转
if(event.getPointerCount()>=2)
{
PointF p1=new PointF(event.getX(0),event.getY(0));
PointF p2=new PointF(event.getX(1),event.getY(1));
float dist=getDist(p1.x, p1.y, p2.x, p2.y);
float scale=dist/startDist;
matrix.set(m);
matrix.postScale(scale,scale,(p1.x+p2.x)/2,(p1.y+p2.y)/2 );
}
}
break;
case MotionEvent.ACTION_UP://最后一根手指抬起
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_OUTSIDE:
state=NONE;
break;
}
img1.setImageMatrix(matrix);
img1.invalidate();
return true;
}
};

public float  getDist(float x1,float y1,float x2,float y2)
{
double value= Math.sqrt((x2-x1)*(x2-x1)+(y2-y1)*(y2-y1));
return (float)value;
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity" >
<ImageView android:id="@+id/img1"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:src="@drawable/s2"
android:scaleType="matrix"
/>
</RelativeLayout>