public class MainActivity extends FragmentActivity {
 
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
 
    if (isFlashSupported()) {
      if (savedInstanceState == null) {
        getSupportFragmentManager().beginTransaction().add(R.id.container, new FlashlightFragment()).commit();
      }
    } else {
      showNoFlashAlert();
    }
  }
 
  private void showNoFlashAlert() {
    new AlertDialog.Builder(this)
        .setMessage(R.string.device_not_support_msg)
        .setIcon(android.R.drawable.ic_dialog_alert).setTitle(R.string.device_not_support_title)
        .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
 
          @Override
          public void onClick(DialogInterface dialog, int which) {
            dialog.dismiss();
            finish();
          }
        }).create().show();
  }
 
  private boolean isFlashSupported() {
    PackageManager pm = getPackageManager();
    return pm.hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
  }
 
  public static class FlashlightFragment extends Fragment implements SurfaceHolder.Callback {
 
    public FlashlightFragment() { }
 
    ImageButton btnSwitch;
    ImageView bg;
    private boolean isLighOn = false;
 
    private Camera camera;
    Camera.Parameters params;
 
    @Override
    public void onStart() {
      super.onStart();
      SurfaceView preview = (SurfaceView) getView().findViewById(R.id.PREVIEW);
      SurfaceHolder mHolder = preview.getHolder();
      mHolder.addCallback(this);
    }
 
    @Override
    public void onPause() {
      super.onPause();
      turnOffFlash();
    }
 
    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
      View view = inflater.inflate(R.layout.fragment_main_activity, container, false);
 
      // flash switch button
      btnSwitch = (ImageButton) view.findViewById(R.id.flashlight_button);
 
      bg = (ImageView) view.findViewById(R.id.flashlight_bg);
 
      // displaying button image
      toggleBgImage();
 
      // Switch button click event to toggle flash on/off
      btnSwitch.setOnClickListener(new View.OnClickListener() {
 
        @Override
        public void onClick(View v) {
          if (isLighOn) {
            turnOffFlash();
          } else {
            turnOnFlash();
          }
        }
      });
 
      return view;
    }
 
    // Turning On flash
    private void turnOnFlash() {
 
      if (!isLighOn) {
        if (camera == null || params == null) {
          return;
        }
        params = camera.getParameters();
        params.setFlashMode(Camera.Parameters.FLASH_MODE_TORCH);
        camera.setParameters(params);
        camera.startPreview();
        isLighOn = true;
 
        toggleBgImage();
      }
 
    }
 
    // Turning Off flash
    private void turnOffFlash() {
 
      if (isLighOn) {
        if (camera == null || params == null) {
          return;
        }
 
        params = camera.getParameters();
        params.setFlashMode(Camera.Parameters.FLASH_MODE_OFF);
        camera.setParameters(params);
        camera.stopPreview();
        isLighOn = false;
 
        toggleBgImage();
      }
    }
 
    private void toggleBgImage() {
      if (isLighOn) {
        bg.setImageResource(R.mipmap.f_on);
      } else {
        bg.setImageResource(R.mipmap.f_off);
      }
    }
 
    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
 
    }
 
    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {
      if (camera != null) {
        camera.stopPreview();
        camera.setPreviewCallback(null);
        camera.release();
        camera = null;
      }
    }
 
    @Override
    public void surfaceCreated(SurfaceHolder holder) {
      if (camera == null) {
        camera = Camera.open();
        params = camera.getParameters();
        try {
          camera.setPreviewDisplay(holder);
        } catch (IOException e) {
          camera.release();
          camera = null;
        }
      }
 
      turnOnFlash();
    }
 
  }
 
 
}

<RelativeLayout
  xmlns:android=\"http://schemas.android.com/apk/res/android\"
  android:layout_width=\"match_parent\"
  android:layout_height=\"match_parent\"
  >
 
  <SurfaceView
    android:id=\"@+id/PREVIEW\"
    android:layout_width=\"1dp\"
    android:layout_height=\"1dp\"/>
 
  <ImageView
    android:id=\"@+id/flashlight_bg\"
    android:layout_width=\"match_parent\"
    android:layout_height=\"match_parent\"
    android:src=\"@mipmap/f_on\"
    android:scaleType=\"centerCrop\"
    />
 
  <ImageButton
    android:id=\"@+id/flashlight_button\"
    android:layout_width=\"100dp\"
    android:layout_height=\"200dp\"
    android:layout_centerInParent=\"true\"
    android:background=\"@android:color/transparent\"
    android:text=\"fuck\"/>
 
</RelativeLayout>

<FrameLayout xmlns:android=\"http://schemas.android.com/apk/res/android\"
       android:id=\"@+id/container\"
       android:layout_width=\"match_parent\"
       android:layout_height=\"match_parent\"
       />

<?xml version=\"1.0\" encoding=\"utf-8\"?>
<manifest xmlns:android=\"http://schemas.android.com/apk/res/android\"
  package=\"com.liujinghuiuncleapp.app.tool.flashlight\" >
 
  <uses-permission android:name=\"android.permission.CAMERA\" />
  <uses-permission android:name=\"android.permission.FLASHLIGHT\" />
 
  <uses-feature android:name=\"android.hardware.camera\" />
  <uses-feature android:name=\"android.hardware.camera.flash\" />
 
  <application
    android:allowBackup=\"true\"
    android:icon=\"@mipmap/ic_launcher\"
    android:theme=\"@style/AppTheme\"
    android:label=\"@string/app_name\" >
    <activity
      android:name=\".MainActivity\"
      android:label=\"@string/app_name\" >
      <intent-filter>
        <action android:name=\"android.intent.action.MAIN\" />
 
        <category android:name=\"android.intent.category.LAUNCHER\" />
      </intent-filter>
    </activity>
  </application>
 
</manifest>