实现图片的拖拽缩放功能

用的touchListener方法

public class Second extends AppCompatActivity implements View.OnTouchListener{

private ImageView imageView;

private Matrix matrix = new Matrix();
private Matrix savedMatrix = new Matrix();

private static final int NONE = 0;
private static final int DRAG = 1;
private static final int ZOOM = 2;
private int mode = NONE;

// 第一个按下的手指的点
private PointF startPoint = new PointF();
// 两个按下的手指的触摸点的中点
private PointF midPoint = new PointF();
// 初始的两个手指按下的触摸点的距离
private float oriDis = 1f;

@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.second);
DisplayImageOptions options = new DisplayImageOptions.Builder()
.cacheInMemory(true)
.cacheOnDisk(true)
.build();

imageView = (ImageView) findViewById(R.id.tupian);
Intent intent = getIntent();
String url = intent.getStringExtra("url");
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ImageLoader.getInstance().displayImage(url,imageView,options);
imageView.setOnTouchListener(Second.this);
}

@Override
public boolean onTouch(View v, MotionEvent event) {
ImageView view = (ImageView) v;

// 可以处理处理多点触摸
//        http://blog.csdn.net/fobdddf/article/details/19479153 //        http://blog.sina.com.cn/s/blog_60e96a410100mjd2.html //        https://my.oschina.net/qianjia/blog/109282 switch (event.getAction() & MotionEvent.ACTION_MASK) {
case MotionEvent.ACTION_DOWN:
// 第一个手指按下事件
matrix.set(view.getImageMatrix());
savedMatrix.set(matrix);
startPoint.set(event.getX(), event.getY());
//拖动
mode = DRAG;
break;
case MotionEvent.ACTION_POINTER_DOWN:
//            event.getX(012)
// 第二个手指按下事件
oriDis = distance(event);
if (oriDis > 10f) {
savedMatrix.set(matrix);
midPoint = middle(event);
//标记成缩放状态
mode = ZOOM;
}
break;
case MotionEvent.ACTION_UP:
case MotionEvent.ACTION_POINTER_UP:
// 手指放开事件
mode = NONE;
break;
case MotionEvent.ACTION_MOVE:
// 手指滑动事件
if (mode == DRAG) {
// 是一个手指拖动
matrix.set(savedMatrix);
//移动图片
matrix.postTranslate(event.getX() - startPoint.x, event.getY()
- startPoint.y);
} else if (mode == ZOOM) {
// 两个手指滑动
float newDist = distance(event);
if (newDist > 10f) {
matrix.set(savedMatrix);
float scale = newDist / oriDis;
//图片的缩放
matrix.postScale(scale, scale, midPoint.x, midPoint.y);
}
}
break;
}

// 设置ImageView的Matrix
view.setImageMatrix(matrix);

b1d0
return true;
}

// 计算两个触摸点之间的距离
private float distance(MotionEvent event) {
//获取第0跟手指和第一根手指的坐标
float x = event.getX(0) - event.getX(1);
float y = event.getY(0) - event.getY(1);
return (float) Math.sqrt(x * x + y * y);
}

// 计算两个触摸点的中点
private PointF middle(MotionEvent event) {
float x = event.getX(0) + event.getX(1);
float y = event.getY(0) + event.getY(1);
return new PointF(x / 2, y / 2);
}
}