使用Camera2 API开发一个相机Demo
Camera2介绍
从Android 5.0开始，Google引入了一套全新的相机框架Camera2，并且废弃了旧的相机框架Camera1。Camera2的出现给相机应用程序带来了巨大的变革，它给相机应用层提供了更多的相机控制权限。国内的众多手机厂商系统相机应用里形式多样的快拍、连拍、自动构图、延时摄影、自动构图等功能，本质上都是通过对Camera2 和HAL3对深入挖掘后构建出的高度复杂的应用程序。
Android设备和Camera器件是通过pipeline的概念将两者串联的，pipeline即一整套Camera处理流程，可以抽象成一个CaptureRequestSession过程，在这个过程中由Android系统发送CaptureRequest，Camera返回元数据MetaData来进行交互，预览和拍照等数据的传递时通过Surface进行。
以Activity生命周期的顺序作为切入点，使用Camera2开发一款相机Demo：
1、onCreate
在onCreate()时，主要做自定义相机工具类CameraUtils的初始化，相机初始化、视图初始化的工作；
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
// 通过CameraUtils的初始化方法，给CameraUtils拿到CameraManager对象
CameraUtils.init(this);
// 初始化相机，获取CameraManager和CameraID、画面尺寸
initCamera();
// 初始化界面视图
initViews();
}
1.1、相机工具类的初始化
自定义相机工具类CameraUtils的初始化主要是为了创建一个CameraManager对象mCameraManager；
public static void init(Context context){
if(appContext == null){
// 由于该方法是静态的，将上下文生命周期与应用程序绑定，防止内存泄露
appContext = context.getApplicationContext();
mCameraManager = (CameraManager) appContext.getSystemService(Context.CAMERA_SERVICE);
}
}
1.2、相机初始化
相机初始化的目的主要是为了获取CameraId，以及根据CameraID，得到对应相机支持的所有画幅的尺寸outputSizes
private void initCamera(){
// 拿到CameraManager对象mCameraManager
mCameraManager = CameraUtils.getInstance().getCameraManager();
// 获取后置镜头ID
cameraId = CameraUtils.getInstance().getBackCameraId();
// 根据后置镜头ID，获取支持的所有输出尺寸
outputSizes = CameraUtils.getInstance().getCameraOutputSizes(cameraId, SurfaceTexture.class);
// 获取第一个尺寸
photoSize = outputSizes.get(0);
}
1.2.1、获取CameraId
拿到后置摄像头的CameraID；
LENS_FACING_FRONT，指的是前置摄像头，CameraID一般为1；
LENS_FACING_BACK，指的是后置摄像头，CameraID一般为0；
public String getCameraId(boolean useFront){
try {
for (String cameraId: mCameraManager.getCameraIdList()) {
CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(cameraId);
//获取当前CameraId对应相机的朝向
int cameraFacing = characteristics.get(CameraCharacteristics.LENS_FACING);
if(useFront){
if(cameraFacing == CameraCharacteristics.LENS_FACING_FRONT){
Log.d(TAG, "前置：getCameraId: "+cameraId+",cameraFacing:"+cameraFacing);
return cameraId;
}
}else {
if(cameraFacing == CameraCharacteristics.LENS_FACING_BACK){
Log.d(TAG, "后置：getCameraId: "+cameraId+",cameraFacing:"+cameraFacing);
return cameraId;
}
}
}
} catch (CameraAccessException e) {
Log.e(TAG, "getCameraId: 获取相机信息异常",e);
}
return null;
}
以笔者手上的一台Xiaomi 12 Pro为例，调用Camera2 APImCameraManager.getCameraIdList()返回的结果是[0,1],表示后摄和前摄的id；后摄characteristics.get(CameraCharacteristics.LENS_FACING)返回的结果是1，前摄返回的结果是0；
1.2.2、拿到对应Camera所支持的所有的outputSizes
首先通过CameraManager对象调用getCameraCharacteristics()方法，拿到对应CameraID的characteristics信息，然后使用characteristics调用get方法传入SCALER_STREAM_CONFIGURATION_MAP常量，拿到config信息；再通过config对象调用getOutputSizes(clz)方法得到该相机所支持的所有的画幅尺寸列表。
public List<Size> getCameraOutputSizes(String cameraId, Class clz){
try {
CameraCharacteristics characteristics = mCameraManager.getCameraCharacteristics(cameraId);
StreamConfigurationMap configs = characteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
List<Size> sizes = Arrays.asList(configs.getOutputSizes(clz));
Collections.sort(sizes, new Comparator<Size>() {
@Override
public int compare(Size o1, Size o2) {
return o2.getWidth() * o2.getHeight() - o1.getWidth() * o1.getHeight();
}
});
return sizes;
} catch (CameraAccessException e) {
Log.e(TAG, "getCameraOutputSizes: 获取相机信息异常", e);
}
return null;
}
1.3、Activity视图初始化
加载Activity的布局文件，再对快门按键添加监听器，实现快门功能；
private void initViews() {
// 设置页面布局
setContentView(R.layout.activity_main);
btnPhoto = findViewById(R.id.btn_photo);
// 快门按钮设置监听
btnPhoto.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// 设置点击时间回调，触发拍照
takePhoto();
}
});
previewView = findViewById(R.id.preview_view);
}
1.4 拍照takePhoto
cameraDevice.createCaptureRequest()传入一个拍照的标志位即可返回一个CaptureRequest.Builder对象；cameraDevice.TEMPLATE_STILL_CAPTURE表示构建的请求为拍照。
| 参数 | 功能 |
|---|---|
| TEMPLATE_PREVIEW | 用于配置预览的模板 |
| TEMPLATE_RECORD | 用于视频录制的模板 |
| TEMPLATE_STILL_CAPTURE | 用于拍照的模板 |
| TEMPLATE_VIDEO_SNAPSHOT | 用于在录制视频过程中支持拍照的模板 |
| TEMPLATE_MANUAL | 用于自己手动配置大部分参数的模板 |
private void takePhoto() {
try {
photoRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_STILL_CAPTURE);
cameraOrientation = PHOTO_ORI.get(displayRotation);
photoRequestBuilder.set(CaptureRequest.JPEG_ORIENTATION,cameraOrientation);
photoRequestBuilder.addTarget(photoSurface);
photoRequest = photoRequestBuilder.build();
captureSession.stopRepeating();
captureSession.capture(photoRequest,sessionCaptureCallback,null);
// 启动一个新线程来播放声音
new Thread(this::shutterSound).start();
} catch (CameraAccessException e) {
Log.e(TAG, "takePhoto: 相机访问异常",e);
}
}
2、onResume
在onResume中，首先检查是否授予了相机权限，如果没有权限则走申请权限的步骤；如果有权限，则判断预览视图是否可用，如果可用则打开相机，如果不可用，添加预览视图监听器；传入预览视图监听器对象。
@Override
protected void onResume() {
super.onResume();
if(checkPermission()){
if(previewView.isAvailable()){
openCamera();
}else {
previewView.setSurfaceTextureListener(surfaceTextureListener);
}
}else {
requestPermission();
}
}
2.1、权限管理
2.1.1、检查权限
private boolean checkPermission(){
return ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED;
}
2.1.2、申请权限
private void requestPermission(){
ActivityCompat.requestPermissions(this,new String[]{Manifest.permission.CAMERA},PERMISSION_REQUEST_CODE);
}
申请权限要定义权限申请结果回调方法：
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode) {
case PERMISSION_REQUEST_CODE:
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED) {
Toast.makeText(getApplicationContext(), "相机权限已授权", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(getApplicationContext(), "已拒绝相机权限", Toast.LENGTH_SHORT).show();
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
!= PackageManager.PERMISSION_GRANTED) {
showMessageOkCancel("你应该授权相机权限，否则无法使用相机",
new DialogInterface.OnClickListener() {
@Override
public void onClick(DialogInterface dialog, int which) {
requestPermission();
}
});
}
}
}
}
如果用户没有及时授权，需要弹出对话框提示用户授权：
private void showMessageOkCancel(String message, DialogInterface.OnClickListener okListener){
new AlertDialog.Builder(Camera.this)
.setMessage(message)
.setPositiveButton("ok",okListener)
.setNegativeButton("Cancel",null)
.create()
.show();
}
2.2、检查预览是否可用
如果可用：
2.2.1、打开相机
@SuppressLint("MissingPermission")
private void openCamera(){
try {
displayOrientation = this.getWindowManager().getDefaultDisplay().getOrientation();
if(displayOrientation == Surface.ROTATION_0 || displayOrientation == Surface.ROTATION_180){
previewView.setAspectRation(photoSize.getHeight(),photoSize.getWidth());
}else {
previewView.setAspectRation(photoSize.getWidth(),photoSize.getHeight());
}
configureTransform(previewView.getWidth(),previewView.getHeight());
mCmameraManager.openCamera(cameraId,cameraStateCallback,null);
} catch (CameraAccessException e) {
Log.e(TAG, "openCamera: 相机访问异常",e);
}
}
配置预览尺寸：
private void configureTransform(int viewWidth,int viewHeight){
if(null == previewView || null == photoSize){
return;
}
int rotation = this.getWindowManager().getDefaultDisplay().getRotation();
Matrix matrix = new Matrix();
RectF viewRect = new RectF(0, 0, viewWidth, viewHeight);
RectF bufferRect = new RectF(0, 0, photoSize.getHeight(), photoSize.getWidth());
float centerX = viewRect.centerX();
float centerY = viewRect.centerY();
if(Surface.ROTATION_90 == rotation || Surface.ROTATION_270 == rotation){
bufferRect.offset(centerX - bufferRect.centerX(), centerY - bufferRect.centerY());
matrix.setRectToRect(viewRect, bufferRect, Matrix.ScaleToFit.FILL);
float scale = Math.max(
(float) viewHeight / photoSize.getHeight(),
(float) viewWidth / photoSize.getWidth());
matrix.postScale(scale, scale, centerX, centerY);
matrix.postRotate(90 * (rotation - 2), centerX, centerY);
} else if (Surface.ROTATION_180 == rotation) {
matrix.postRotate(180,centerX,centerY);
}
previewView.setTag(matrix);
}
定义相机回调：
CameraDevice.StateCallback cameraStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(@NonNull CameraDevice camera) {
Log.d(TAG, "onOpened: 相机已经启动");
// 初始化ImageReader和Surface
initReaderAndSurface();
cameraDevice = camera;
try {
SurfaceTexture surfaceTexture = previewView.getSurfaceTexture();
if(surfaceTexture == null){
return;
}
surfaceTexture.setDefaultBufferSize(photoSize.getWidth(),photoSize.getHeight());
previewSurface = new Surface(surfaceTexture);
previewRequestBuilder = cameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
previewRequestBuilder.addTarget(previewSurface);
previewRequest = previewRequestBuilder.build();
cameraDevice.createCaptureSession(Arrays.asList(previewSurface,photoSurface),sessionsStateCallback,null);
} catch (CameraAccessException e) {
Log.e(TAG, "onOpened: 相机访问异常",e);
}
}
@Override
public void onDisconnected(@NonNull CameraDevice camera) {
Log.d(TAG, "onDisconnected: 相机已断开连接");
}
@Override
public void onError(@NonNull CameraDevice camera, int error) {
Log.d(TAG, "onError: 相机打开出错");
}
};
创建捕获请求时，需要定义会话状态回调：
CameraCaptureSession.StateCallback sessionsStateCallback = new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession session) {
if(null == cameraDevice){
return;
}
captureSession = session;
try {
captureSession.setRepeatingRequest(previewRequest,null,null);
} catch (CameraAccessException e) {
Log.e(TAG, "onConfigured: 相机访问异常",e);
}
}
@Override
public void onConfigureFailed(@NonNull CameraCaptureSession session) {
}
};
如果不可用：
2.2.2、设置预览监听器
定义预览监听回调
``` java TextureView.SurfaceTextureListener surfaceTextureListener = new TextureView.SurfaceTextureListener() { @Override public void onSurfaceTextureAvailable(@NonNull SurfaceTexture surface, int width, int height) { openCamera(); }
@Override
public void onSurfaceTextureSizeChanged(@NonNull SurfaceTexture surface, int width, int height) {
configureTransform(width,height);
}
@Override
public boolean onSurfaceTextureDestroyed(@NonNull SurfaceTexture surface) {
return false;
}
@Override
public void onSurfaceTextureUpdated(@NonNull SurfaceTexture surface) {
}
}; ```