Java Code of the Torch Flashlight App on the SSaurel's Blog

MainActivity.java

package com.ssaurel.mytorch;

import android.Manifest;
import android.content.Context;
import android.content.pm.PackageManager;
import android.hardware.camera2.CameraAccessException;
import android.hardware.camera2.CameraManager;
import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.view.View;
import android.widget.Button;
import android.widget.ImageView;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

  private Button buttonEnable;
  private ImageView imageFlashlight;
  private static final int CAMERA_REQUEST = 50;
  private boolean flashLightStatus = false;

  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    imageFlashlight = (ImageView) findViewById(R.id.imageFlashlight);
    buttonEnable = (Button) findViewById(R.id.buttonEnable);

    final boolean hasCameraFlash = getPackageManager().
            hasSystemFeature(PackageManager.FEATURE_CAMERA_FLASH);
    boolean isEnabled = ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
                        == PackageManager.PERMISSION_GRANTED;

    buttonEnable.setEnabled(!isEnabled);
    imageFlashlight.setEnabled(isEnabled);
    buttonEnable.setOnClickListener(new View.OnClickListener() {
       @Override
       public void onClick(View view) {
          ActivityCompat.requestPermissions(MainActivity.this, new String[] {Manifest.permission.CAMERA}, CAMERA_REQUEST);
       }
    });

    imageFlashlight.setOnClickListener(new View.OnClickListener() {
      @Override
      public void onClick(View view) {
        if (hasCameraFlash) {
          if (flashLightStatus)
            flashLightOff();
          else
            flashLightOn();
        } else {
          Toast.makeText(MainActivity.this, "No flash available on your device", 
            Toast.LENGTH_SHORT).show();
        }
      }
    });
  }

  private void flashLightOn() {
    CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
    
	try {
      String cameraId = cameraManager.getCameraIdList()[0];
      cameraManager.setTorchMode(cameraId, true);
      flashLightStatus = true;
      imageFlashlight.setImageResource(R.drawable.btn_switch_on);
    } catch (CameraAccessException e) {
    }
  }

  private void flashLightOff() {
    CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);

	try {
      String cameraId = cameraManager.getCameraIdList()[0];
      cameraManager.setTorchMode(cameraId, false);
      flashLightStatus = false;
      imageFlashlight.setImageResource(R.drawable.btn_switch_off);
    } catch (CameraAccessException e) {
    }
  }

  @Override
  public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
    switch(requestCode) {
      case CAMERA_REQUEST :
        if (grantResults.length > 0  &&  grantResults[0] == PackageManager.PERMISSION_GRANTED) {
          buttonEnable.setEnabled(false);
          buttonEnable.setText("Camera Enabled");
          imageFlashlight.setEnabled(true);
        } else {
          Toast.makeText(MainActivity.this, "Permission Denied for the Camera", Toast.LENGTH_SHORT).show();
        }
      break;
    }
  }
}