Simple-Camera/app/src/main/java/com/simplemobiletools/camera/MainActivity.java

package com.simplemobiletools.camera;

import android.hardware.Camera;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;

public class MainActivity extends AppCompatActivity {
    private static final String TAG = MainActivity.class.getSimpleName();
    private Camera camera;
    private boolean isOpen;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    @Override
    protected void onResume() {
        super.onResume();
        openCamera();
    }

    @Override
    protected void onPause() {
        super.onPause();
        releaseCamera();
    }

    private void openCamera() {
        isOpen = false;

        try {
            releaseCamera();
            camera = Camera.open();
            isOpen = (camera != null);
        } catch (Exception e) {
            Log.e(TAG, "openCamera exception " + e.getMessage());
        }
    }

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