如何实现双指缩放？

XML

<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"
android:paddingBottom="@dimen/activity_vertical_margin"
android:paddingLeft="@dimen/activity_horizontal_margin"
android:paddingRight="@dimen/activity_horizontal_margin"
android:paddingTop="@dimen/activity_vertical_margin"
tools:context=".MainActivity" >

<TextView
    android:id="@+id/pinchTitleText"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@string/pinch_title" />

<ImageView
    android:id="@+id/imageView"
    android:layout_width="300dp"
    android:layout_height="300dp"
    android:layout_below="@+id/pinchTitleText"
    android:scaleType="matrix"
    android:src="@drawable/zoom"
    android:maxHeight="100dp"
    android:maxWidth="50dp" />

</RelativeLayout>

活动

public class PinchZoomActivity extends Activity {
private ImageView imageView;
private ScaleGestureDetector scaleGestureDetector;
private Matrix matrix = new Matrix();

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    imageView = (ImageView)findViewById(R.id.imageView);
    scaleGestureDetector = new ScaleGestureDetector(this,new ScaleListener());
}

@Override
public boolean onTouchEvent(MotionEvent ev) {
    scaleGestureDetector.onTouchEvent(ev);
    return true;
}

private class ScaleListener extends ScaleGestureDetector.
        SimpleOnScaleGestureListener {
    @Override
    public boolean onScale(ScaleGestureDetector detector) {
        float scaleFactor = detector.getScaleFactor();
        scaleFactor = Math.max(0.1f, Math.min(scaleFactor, 5.0f));
        matrix.setScale(scaleFactor, scaleFactor);
        imageView.setImageMatrix(matrix);
        return true;
    }
}
}

要缩放图片，最好在 中显示它WebView，life hack 是旧的，但似乎在工作。缩放应该是默认的。至少，你在这里

https://github.com/chrisbanes/PhotoView https://github.com/ongakuer/PhotoDraweeView

如果通过上传图片Fresko则使用第二个

可能最简单的方法是复制此类扩展ImageView： https ://github.com/MikeOrtiz/TouchImageView/blob/master/src/com/ortiz/touch/TouchImageView.java

在标记文件代码中，xml写入：

<_имя_вашего_пакета_.TouchImageView/>

祝你好运！