how to make torch app in android

activity_main.xml:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout1"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" >

    <Button
        android:id="@+id/buttonFlashlight"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerVertical="true"
        android:layout_centerHorizontal="true"
        android:text="Torch" />

</RelativeLayout>

MainActivity.java:

import android.app.Activity;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.Camera;
import android.hardware.Camera.Parameters;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class FlashLightActivity extends Activity {

 //flag to detect flash is on or off
 private boolean isLighOn = false;

 private Camera camera;

 private Button button;

 @Override
 protected void onStop() {
  super.onStop();

  if (camera != null) {
   camera.release();
  }
 }

 @Override
 public void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  setContentView(R.layout.main);

  button = (Button) findViewById(R.id.buttonFlashlight);

  Context context = this;
  PackageManager pm = context.getPackageManager();

  // if device support camera?
  if (!pm.hasSystemFeature(PackageManager.FEATURE_CAMERA)) {
   Log.e("err", "Device has no camera!");
   return;
  }

  camera = Camera.open();
  final Parameters p = camera.getParameters();

  button.setOnClickListener(new OnClickListener() {

   @Override
   public void onClick(View arg0) {

    if (isLighOn) {

     Log.i("info", "torch is turn off!");

     p.setFlashMode(Parameters.FLASH_MODE_OFF);
     camera.setParameters(p);
     camera.stopPreview();
     isLighOn = false;

    } else {

     Log.i("info", "torch is turn on!");

     p.setFlashMode(Parameters.FLASH_MODE_TORCH);

     camera.setParameters(p);
     camera.startPreview();
     isLighOn = true;

    }

   }
  });

 }
}

Add Permissions to your manifest:

 <uses-permission android:name="android.permission.CAMERA" />
    <uses-feature android:name="android.hardware.camera" />