Android Camera2 Bare Minimum Code Sample

Google has replaced camera API with camera2 API a few years ago. I guess it is a good thing that Google is working hard to improve Android, personally I think camera2 API is just so difficult. Compared to the deprecated camera API, it requires so much more code.

I am trying to understand this new camera2 API, and it is just not easy. I looked at Google's Camera2Basic sample code, it is still daunting for Android beginners like myself. Well, here is my attempt to trim down this fat sample code into the bare minimum so that it is easier to understand the fundamentals of the camera2 API.

All it does is to connect to a camera and display its preview to the screen. No capture, no manual focus, no error checks, etc. I am not happy that even this bare-bone app requires so many lines. Anyways, I will add more functionalities in the upcoming post.

	<?xml version="1.0" encoding="utf-8"?>
	<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
	xmlns:app="http://schemas.android.com/apk/res-auto"
	xmlns:tools="http://schemas.android.com/tools"
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	tools:context="com.unixnme.camera2.MainActivity">
	<TextureView
	android:layout_width="match_parent"
	android:layout_height="match_parent"
	android:id="@+id/preview"/>
	</android.support.constraint.ConstraintLayout>

view raw activity_main.xml hosted with ❤ by GitHub

	<?xml version="1.0" encoding="utf-8"?>
	<manifest xmlns:android="http://schemas.android.com/apk/res/android"
	package="com.unixnme.camera2">
	<uses-permission android:name="android.permission.CAMERA" />
	<uses-feature android:name="android.hardware.camera.level.full" />
	<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>

view raw AndroidManifest.xml hosted with ❤ by GitHub

	package com.unixnme.camera2;
	import android.Manifest;
	import android.content.Context;
	import android.content.pm.PackageManager;
	import android.graphics.SurfaceTexture;
	import android.hardware.camera2.CameraCaptureSession;
	import android.hardware.camera2.CameraCharacteristics;
	import android.hardware.camera2.CameraDevice;
	import android.hardware.camera2.CameraManager;
	import android.hardware.camera2.CaptureRequest;
	import android.hardware.camera2.params.StreamConfigurationMap;
	import android.support.annotation.NonNull;
	import android.support.v4.content.ContextCompat;
	import android.support.v7.app.AppCompatActivity;
	import android.os.Bundle;
	import android.util.Log;
	import android.util.Size;
	import android.view.Surface;
	import android.view.TextureView;
	import java.util.Arrays;
	import java.util.Collections;
	public class MainActivity extends AppCompatActivity {
	private TextureView mTextureView;
	final private static String TAG = MainActivity.class.getSimpleName();
	// preview related ////////////////////////////////////////////////////////////////
	private CaptureRequest.Builder mCaptureRequestbuilder;
	private final TextureView.SurfaceTextureListener mSurfaceTextureListener
	= new TextureView.SurfaceTextureListener() {
	@Override
	public void onSurfaceTextureAvailable(SurfaceTexture texture, int width, int height) {
	openCamera(width, height);
	}
	@Override
	public void onSurfaceTextureSizeChanged(SurfaceTexture texture, int width, int height) {
	}
	@Override
	public boolean onSurfaceTextureDestroyed(SurfaceTexture texture) {
	return true;
	}
	@Override
	public void onSurfaceTextureUpdated(SurfaceTexture texture) {
	}
	};
	final private CameraCaptureSession.StateCallback mCaptureStateCallback = new CameraCaptureSession.StateCallback() {
	@Override
	public void onConfigured(@NonNull CameraCaptureSession cameraCaptureSession) {
	try {
	cameraCaptureSession.setRepeatingRequest(mCaptureRequestbuilder.build(), null, null);
	} catch (Throwable t) {
	handleException(t);
	}
	}
	@Override
	public void onConfigureFailed(@NonNull CameraCaptureSession cameraCaptureSession) {
	}
	};
	private void createCameraPreviewSession() {
	SurfaceTexture texture = mTextureView.getSurfaceTexture();
	texture.setDefaultBufferSize(mSize.getWidth(), mSize.getHeight());
	Surface surface = new Surface(texture);
	try {
	mCaptureRequestbuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
	mCaptureRequestbuilder.addTarget(surface);
	mCameraDevice.createCaptureSession(Collections.singletonList(surface), mCaptureStateCallback, null);
	} catch (Throwable t) {
	handleException(t);
	}
	}
	// camera related /////////////////////////////////////////////////////////////
	private CameraDevice mCameraDevice;
	private Size mSize;
	final private CameraDevice.StateCallback mStateCallback = new CameraDevice.StateCallback() {
	@Override
	public void onOpened(@NonNull CameraDevice cameraDevice) {
	mCameraDevice = cameraDevice;
	createCameraPreviewSession();
	}
	@Override
	public void onDisconnected(@NonNull CameraDevice cameraDevice) {
	mCameraDevice = null;
	}
	@Override
	public void onError(@NonNull CameraDevice cameraDevice, int i) {
	mCameraDevice = null;
	}
	};
	private void openCamera(int width, int height) {
	if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
	!= PackageManager.PERMISSION_GRANTED) {
	requestCameraPermission();
	return;
	}
	CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
	try {
	String cameraId = cameraManager.getCameraIdList()[0];
	CameraCharacteristics characteristics
	= cameraManager.getCameraCharacteristics(cameraId);
	StreamConfigurationMap map = characteristics.get(
	CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
	mSize = map.getOutputSizes(SurfaceTexture.class)[0];
	cameraManager.openCamera(cameraId, mStateCallback, null);
	} catch (Throwable t) {
	handleException(t);
	}
	}
	private void closeCamera() {
	try {
	if (null != mCameraDevice)
	mCameraDevice.close();
	} catch (Throwable t) {
	handleException(t);
	}
	}
	// activity lifecycle related /////////////////////////////////////////////////
	@Override
	protected void onCreate(Bundle savedInstanceState) {
	super.onCreate(savedInstanceState);
	setContentView(R.layout.activity_main);
	mTextureView = findViewById(R.id.preview);
	}
	@Override
	protected void onResume() {
	super.onResume();
	// we open up camera after the textureview is available
	// either way, we will call openCamera
	if (mTextureView.isAvailable()) {
	// call now
	int width = mTextureView.getWidth();
	int height = mTextureView.getHeight();
	openCamera(width, height);
	} else {
	// call from the listener callback
	mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
	}
	}
	@Override
	public void onPause() {
	super.onPause();
	closeCamera();
	}
	// request related ///////////////////////////////////////////////////////////////
	private static final int REQUEST_CAMERA_PERMISSION = 1;
	private void requestCameraPermission() {
	requestPermissions(new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION);
	}
	@Override
	public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions,
	@NonNull int[] grantResults) {
	if (requestCode == REQUEST_CAMERA_PERMISSION) {
	if (grantResults.length != 1 || grantResults[0] != PackageManager.PERMISSION_GRANTED) {
	// permissio not granted; quit the app
	this.finish();
	}
	} else {
	super.onRequestPermissionsResult(requestCode, permissions, grantResults);
	}
	}
	// Exceptions ////////////////////////////////////////////////////////////////////////
	private void handleException(Throwable t) {
	Log.d(TAG, t.getMessage());
	t.printStackTrace();
	}
	}

view raw MainActivity.java hosted with ❤ by GitHub