本文已獲得作者授權，本文作者：cain_huang
原文連結：https://www.jianshu.com/p/9e0f3fc5a3b4
Android使用 Camera API + SurfaceView 方式進行預覽拍照。
SurfaceView 的創建以及回調創建一個SurfaceView，並實現SurfaceHolder的回調。
由於Camera在SurfaceView中是通過SurfaceHolder 使得Surfaceview能夠預覽Camera返回的數據，因此我們需要實現SurfaceHolder 的回調，實現代碼如下：
public class CameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback {
private static final String TAG = CameraSurfaceView.class.getSimpleName();
private SurfaceHolder mSurfaceHolder;
public CameraSurfaceView(Context context) {
super(context);
init();
}
public CameraSurfaceView(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public CameraSurfaceView(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init();
}
private void init() {
mSurfaceHolder = getHolder();
mSurfaceHolder.addCallback(this);
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
CameraUtils.openFrontalCamera(CameraUtils.DESIRED_PREVIEW_FPS);
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
CameraUtils.startPreviewDisplay(holder);
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
CameraUtils.releaseCamera();
}
}
CameraUtils 輔助類主要是Camera API 的一些操作，比如打開相機、開始預覽、停止預覽、切換相機、設置預覽參數等操作，具體實現如下：
public class CameraUtils {
public static final int DEFAULT_WIDTH = 1280;
public static final int DEFAULT_HEIGHT = 720;
public static final int DESIRED_PREVIEW_FPS = 30;
private static int mCameraID = Camera.CameraInfo.CAMERA_FACING_FRONT;
private static Camera mCamera;
private static int mCameraPreviewFps;
private static int mOrientation = 0;
public static void openFrontalCamera(int expectFps) {
if (mCamera != null) {
throw new RuntimeException("camera already initialized!");
}
Camera.CameraInfo info = new Camera.CameraInfo();
int numCameras = Camera.getNumberOfCameras();
for (int i = 0; i < numCameras; i++) {
Camera.getCameraInfo(i, info);
if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
mCamera = Camera.open(i);
mCameraID = info.facing;
break;
}
}
if (mCamera == null) {
mCamera = Camera.open();
mCameraID = Camera.CameraInfo.CAMERA_FACING_BACK;
}
if (mCamera == null) {
throw new RuntimeException("Unable to open camera");
}
Camera.Parameters parameters = mCamera.getParameters();
mCameraPreviewFps = CameraUtils.chooseFixedPreviewFps(parameters, expectFps * 1000);
parameters.setRecordingHint(true);
mCamera.setParameters(parameters);
setPreviewSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
setPictureSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
mCamera.setDisplayOrientation(mOrientation);
}
public static void openCamera(int cameraID, int expectFps) {
if (mCamera != null) {
throw new RuntimeException("camera already initialized!");
}
mCamera = Camera.open(cameraID);
if (mCamera == null) {
throw new RuntimeException("Unable to open camera");
}
mCameraID = cameraID;
Camera.Parameters parameters = mCamera.getParameters();
mCameraPreviewFps = CameraUtils.chooseFixedPreviewFps(parameters, expectFps * 1000);
parameters.setRecordingHint(true);
mCamera.setParameters(parameters);
setPreviewSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
setPictureSize(mCamera, CameraUtils.DEFAULT_WIDTH, CameraUtils.DEFAULT_HEIGHT);
mCamera.setDisplayOrientation(mOrientation);
}
public static void startPreviewDisplay(SurfaceHolder holder) {
if (mCamera == null) {
throw new IllegalStateException("Camera must be set when start preview");
}
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
e.printStackTrace();
}
}
public static void switchCamera(int cameraID, SurfaceHolder holder) {
if (mCameraID == cameraID) {
return;
}
mCameraID = cameraID;
releaseCamera();
openCamera(cameraID, CameraUtils.DESIRED_PREVIEW_FPS);
startPreviewDisplay(holder);
}
public static void releaseCamera() {
if (mCamera != null) {
mCamera.stopPreview();
mCamera.release();
mCamera = null;
}
}
public static void startPreview() {
if (mCamera != null) {
mCamera.startPreview();
}
}
public static void stopPreview() {
if (mCamera != null) {
mCamera.stopPreview();
}
}
public static void takePicture(Camera.ShutterCallback shutterCallback,
Camera.PictureCallback rawCallback,
Camera.PictureCallback pictureCallback) {
if (mCamera != null) {
mCamera.takePicture(shutterCallback, rawCallback, pictureCallback);
}
}
public static void setPreviewSize(Camera camera, int expectWidth, int expectHeight) {
Camera.Parameters parameters = camera.getParameters();
Camera.Size size = calculatePerfectSize(parameters.getSupportedPreviewSizes(),
expectWidth, expectHeight);
parameters.setPreviewSize(size.width, size.height);
camera.setParameters(parameters);
}
public static Camera.Size getPreviewSize() {
if (mCamera != null) {
return mCamera.getParameters().getPreviewSize();
}
return null;
}
public static void setPictureSize(Camera camera, int expectWidth, int expectHeight) {
Camera.Parameters parameters = camera.getParameters();
Camera.Size size = calculatePerfectSize(parameters.getSupportedPictureSizes(),
expectWidth, expectHeight);
parameters.setPictureSize(size.width, size.height);
camera.setParameters(parameters);
}
public static Camera.Size getPictureSize() {
if (mCamera != null) {
return mCamera.getParameters().getPictureSize();
}
return null;
}
public static Camera.Size calculatePerfectSize(List<Camera.Size> sizes, int expectWidth,
int expectHeight) {
sortList(sizes);
Camera.Size result = sizes.get(0);
boolean widthOrHeight = false;
for (Camera.Size size: sizes) {
if (size.width == expectWidth && size.height == expectHeight) {
result = size;
break;
}
if (size.width == expectWidth) {
widthOrHeight = true;
if (Math.abs(result.height - expectHeight)
> Math.abs(size.height - expectHeight)) {
result = size;
}
}
else if (size.height == expectHeight) {
widthOrHeight = true;
if (Math.abs(result.width - expectWidth)
> Math.abs(size.width - expectWidth)) {
result = size;
}
}
else if (!widthOrHeight) {
if (Math.abs(result.width - expectWidth)
> Math.abs(size.width - expectWidth)
&& Math.abs(result.height - expectHeight)
> Math.abs(size.height - expectHeight)) {
result = size;
}
}
}
return result;
}
private static void sortList(List<Camera.Size> list) {
Collections.sort(list, new Comparator<Camera.Size>() {
@Override
public int compare(Camera.Size pre, Camera.Size after) {
if (pre.width > after.width) {
return 1;
} else if (pre.width < after.width) {
return -1;
}
return 0;
}
});
}
public static int chooseFixedPreviewFps(Camera.Parameters parameters, int expectedThoudandFps) {
List<int[]> supportedFps = parameters.getSupportedPreviewFpsRange();
for (int[] entry : supportedFps) {
if (entry[0] == entry[1] && entry[0] == expectedThoudandFps) {
parameters.setPreviewFpsRange(entry[0], entry[1]);
return entry[0];
}
}
int[] temp = new int[2];
int guess;
parameters.getPreviewFpsRange(temp);
if (temp[0] == temp[1]) {
guess = temp[0];
} else {
guess = temp[1] / 2;
}
return guess;
}
public static int calculateCameraPreviewOrientation(Activity activity) {
Camera.CameraInfo info = new Camera.CameraInfo();
Camera.getCameraInfo(mCameraID, info);
int rotation = activity.getWindowManager().getDefaultDisplay()
.getRotation();
int degrees = 0;
switch (rotation) {
case Surface.ROTATION_0:
degrees = 0;
break;
case Surface.ROTATION_90:
degrees = 90;
break;
case Surface.ROTATION_180:
degrees = 180;
break;
case Surface.ROTATION_270:
degrees = 270;
break;
}
int result;
if (info.facing == Camera.CameraInfo.CAMERA_FACING_FRONT) {
result = (info.orientation + degrees) % 360;
result = (360 - result) % 360;
} else {
result = (info.orientation - degrees + 360) % 360;
}
mOrientation = result;
return result;
}
public static int getCameraID() {
return mCameraID;
}
public static int getPreviewOrientation() {
return mOrientation;
}
public static int getCameraPreviewThousandFps() {
return mCameraPreviewFps;
}
}
在Activity中使用CameraSurfaceview，有Android6.0動態權限申請問題，需要我們判斷相機和存儲權限是否申請了：
public class CameraSurfaceViewActivity extends AppCompatActivity implements View.OnClickListener {
private static final int REQUEST_CAMERA = 0x01;
private CameraSurfaceView mCameraSurfaceView;
private Button mBtnTake;
private Button mBtnSwitch;
private int mOrientation;
private FrameLayout mAspectLayout;
private boolean mCameraRequested;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setContentView(R.layout.activity_camera_surface);
if (ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA)
== PackageManager.PERMISSION_GRANTED) {
initView();
} else {
ActivityCompat.requestPermissions(this,
new String[]{
Manifest.permission.CAMERA,
Manifest.permission.WRITE_EXTERNAL_STORAGE
}, REQUEST_CAMERA);
}
}
private void initView() {
mAspectLayout = (FrameLayout) findViewById(R.id.layout_aspect);;
mCameraSurfaceView = new CameraSurfaceView(this);
mAspectLayout.addView(mCameraSurfaceView);
mOrientation = CameraUtils.calculateCameraPreviewOrientation(CameraSurfaceViewActivity.this);
mBtnTake = (Button) findViewById(R.id.btn_take);
mBtnTake.setOnClickListener(this);
mBtnSwitch = (Button) findViewById(R.id.btn_switch);
mBtnSwitch.setOnClickListener(this);
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode) {
case REQUEST_CAMERA:
if (grantResults.length > 0
&& grantResults[0] == PackageManager.PERMISSION_GRANTED) {
mCameraRequested = true;
initView();
}
break;
}
}
@Override
protected void onResume() {
super.onResume();
if (mCameraRequested) {
CameraUtils.startPreview();
}
}
@Override
protected void onPause() {
super.onPause();
CameraUtils.stopPreview();
}
@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_take:
takePicture();
break;
case R.id.btn_switch:
switchCamera();
break;
}
}
private void takePicture() {
CameraUtils.takePicture(new Camera.ShutterCallback() {
@Override
public void onShutter() {
}
}, null, new Camera.PictureCallback() {
@Override
public void onPictureTaken(byte[] data, Camera camera) {
CameraUtils.startPreview();
Bitmap bitmap = BitmapFactory.decodeByteArray(data, 0, data.length);
if (bitmap != null) {
bitmap = ImageUtils.getRotatedBitmap(bitmap, mOrientation);
String path = Environment.getExternalStorageDirectory() + "/DCIM/Camera/"
+ System.currentTimeMillis() + ".jpg";
try {
FileOutputStream fout = new FileOutputStream(path);
BufferedOutputStream bos = new BufferedOutputStream(fout);
bitmap.compress(Bitmap.CompressFormat.JPEG, 100, bos);
bos.flush();
bos.close();
fout.close();
} catch (IOException e) {
e.printStackTrace();
}
}
CameraUtils.startPreview();
}
});
}
private void switchCamera() {
if (mCameraSurfaceView != null) {
CameraUtils.switchCamera(1 - CameraUtils.getCameraID(), mCameraSurfaceView.getHolder());
mOrientation = CameraUtils.calculateCameraPreviewOrientation(CameraSurfaceViewActivity.this);
}
}
}
由於用到了相機和存儲權限，我們需要在manifest中註冊相機和存儲權限，這裡要說明的是，manifest用use-permission只是聲明了需要使用哪些權限，而我們實際項目中在使用到這兩項權限時，需要你檢查權限是否已經被授權，如果沒授權，則需要請求授權：
<!-- 存儲權限 -->
<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
<!-- 相機權限 -->
<uses-permission android:name="android.permission.CAMERA" />
<uses-permission android:name="android.permission.WAKE_LOCK" />
<uses-permission android:name="android.permission.FLASHLIGHT" />
另外，ImageUtils類的實現如下：
public class ImageUtils {
public static Bitmap getRotatedBitmap(Bitmap bitmap, int rotation) {
Matrix matrix = new Matrix();
matrix.postRotate(rotation);
return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
bitmap.getHeight(), matrix, false);
}
public static Bitmap getFlipBitmap(Bitmap bitmap) {
Matrix matrix = new Matrix();
matrix.setScale(-1, 1);
matrix.postTranslate(bitmap.getWidth(), 0);
return Bitmap.createBitmap(bitmap, 0, 0, bitmap.getWidth(),
bitmap.getHeight(), matrix, false);
}
}
layout如下：
<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.cgfay.camerasample.CameraSurfaceViewActivity">
<FrameLayout
android:id="@+id/layout_aspect"
android:layout_width="match_parent"
android:layout_height="wrap_content">
</FrameLayout>
<LinearLayout
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:orientation="horizontal"
android:layout_gravity="bottom"
android:gravity="center">
<Button
android:id="@+id/btn_take"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="拍照" />
<Button
android:id="@+id/btn_switch"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="切換相機" />
</LinearLayout>
</FrameLayout>
至此，通過SurfaceView + Camera API 預覽拍照功能已經實現。
備註Camera API 在打開相機是在哪個線程，那麼onPreviewFrame回調執行就在哪個線程。
因此，如果要通過onPreviewFrame回調使用預覽數據，則可以通過HandlerThread 異步調用Camera進行操作。
另外一個問題，onPreviewFrame方法中不要執行過於複雜的邏輯操作，這樣會阻塞Camera，無法獲取新的Frame，導致幀率下降。
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