How to implement a pinch for scaling?

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> 

Activity

 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; } } } 

For scaling images, it is better to show it in WebView , life hacking is old, but it seems to be working. Zoom must be defaulted. On a pinch here you

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

If you load pictures through Fresko then use the second