Android imageView Zoom-in and Zoom-Out?

This example demonstrates how do I Zoom In and Zoom Out an android ImageView.

Step 1 − Create a new project in Android Studio, go to File ⇒ New Project and fill all required details to create a new project.

Step 2 − Add the following code to res/layout/activity_main.xml.

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout 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:orientation="vertical"
   android:padding="16dp"
   android:gravity="center"
   tools:context=".MainActivity">
   <ImageView
      android:id="@+id/imageView"
      android:layout_width="match_parent"
      android:layout_height="match_parent"
      android:src="@drawable/image" />
</LinearLayout>

Step 3 − Add the following code to src/MainActivity.java

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.ScaleGestureDetector;
import android.widget.ImageView;
public class MainActivity extends AppCompatActivity {
   private ScaleGestureDetector scaleGestureDetector;
   private float mScaleFactor = 1.0f;
   private ImageView imageView;  
   @Override
   protected void onCreate(Bundle savedInstanceState) {
      super.onCreate(savedInstanceState);
      setContentView(R.layout.activity_main);
      imageView=findViewById(R.id.imageView);
      scaleGestureDetector = new ScaleGestureDetector(this, new ScaleListener());
   }
   @Override
   public boolean onTouchEvent(MotionEvent motionEvent) {
      scaleGestureDetector.onTouchEvent(motionEvent);
      return true;
   }
   private class ScaleListener extends ScaleGestureDetector.SimpleOnScaleGestureListener {
      @Override
      public boolean onScale(ScaleGestureDetector scaleGestureDetector) {
         mScaleFactor *= scaleGestureDetector.getScaleFactor();
         mScaleFactor = Math.max(0.1f, Math.min(mScaleFactor, 10.0f));
         imageView.setScaleX(mScaleFactor);
         imageView.setScaleY(mScaleFactor);
         return true;
      }
   }
}

Step 4 − Add the following code to androidManifest.xml

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android" package="app.com.sample">
   <application
      android:allowBackup="true"
      android:icon="@mipmap/ic_launcher"
      android:label="@string/app_name"
      android:roundIcon="@mipmap/ic_launcher_round"
      android:supportsRtl="true"
      android:theme="@style/AppTheme">
      <activity android:name=".MainActivity">
         <intent-filter>
            <action android:name="android.intent.action.MAIN" />
            <category android:name="android.intent.category.LAUNCHER" />
         </intent-filter>
      </activity>
   </application>
</manifest>

Let's try to run your application. I assume you have connected your actual Android Mobile device with your computer. To run the app from android studio, open one of your project's activity files and click Run   icon from the toolbar. Select your mobile device as an option and then check your mobile device which will display your default screen −