问题
I am trying to open the camera hardware on a SurfaceView. In the layout, I created a SurfaceView and I open the camera as shown in the code below. When I run the code, the toast in the CameraAvailableCB shows up and says "onCameraAvailable" but nothing appears on the SurfaceView.
How do I show the camera display on the SurfaceView?
Code
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.mBtnCapture = (Button) findViewById(R.id.actMain_btn_capture);
this.mSurfaceView = (SurfaceView) findViewById(R.id.actMain_surfaceView);
this.mSurfaceHolder = this.mSurfaceView.getHolder();
this.mSurfaceHolder.addCallback(this);
this.mCameraManager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);
try {
cameraIDsList = this.mCameraManager.getCameraIdList();
for (String id : cameraIDsList) {
Log.v(TAG, "CameraID: " + id);
}
} catch (CameraAccessException e) {
e.printStackTrace();
}
cameraStateCB = new CameraDevice.StateCallback() {
@Override
public void onOpened(CameraDevice camera) {
Toast.makeText(getApplicationContext(), "onOpened", Toast.LENGTH_SHORT).show();
//requesting permission
int permissionCheck = ContextCompat.checkSelfPermission(activity, Manifest.permission.CAMERA);
if (permissionCheck != PackageManager.PERMISSION_GRANTED) {
if (ActivityCompat.shouldShowRequestPermissionRationale(activity, Manifest.permission.CAMERA)) {
} else {
ActivityCompat.requestPermissions(activity, new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUEST_CAMERA);
Toast.makeText(getApplicationContext(), "request permission", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(getApplicationContext(), "PERMISSION_ALREADY_GRANTED", Toast.LENGTH_SHORT).show();
}
//opening the camera
try {
mCameraManager.openCamera(cameraIDsList[1], cameraStateCB, new Handler());
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onDisconnected(CameraDevice camera) {
Toast.makeText(getApplicationContext(), "onDisconnected", Toast.LENGTH_SHORT).show();
}
@Override
public void onError(CameraDevice camera, int error) {
Toast.makeText(getApplicationContext(), "onError", Toast.LENGTH_SHORT).show();
}
};
CameraManager.AvailabilityCallback cameraAvailableCB = new CameraManager.AvailabilityCallback() {
@Override
public void onCameraAvailable(String cameraId) {
super.onCameraAvailable(cameraId);
Toast.makeText(getApplicationContext(), "onCameraAvailable", Toast.LENGTH_SHORT).show();
}
@Override
public void onCameraUnavailable(String cameraId) {
super.onCameraUnavailable(cameraId);
Toast.makeText(getApplicationContext(), "onCameraUnavailable", Toast.LENGTH_SHORT).show();
}
};
this.mCameraManager.registerAvailabilityCallback(cameraAvailableCB, new Handler());
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_CAMERA:
if (grantResults.length > 0 && grantResults[0] == PackageManager.PERMISSION_GRANTED)
// Open Camera
break;
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
Log.w(TAG, "surfaceCreated");
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
Log.w(TAG, "surfaceChanged");
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
Log.w(TAG, "surfaceDestroyed");
}
回答1:
To show preview from camera using Camera2 API you should do the following steps:
- Get permission to use camera device
- Using CameraManager open connection to a camera
- Have prepared Surface for preview
- Using opened camera device and desired surfaces (it can include not only preview surface) create CaptureSession
- After CaptureSession created you need to create and configure CaptureRequest and submit it to CaptureSession
Need to notice that preparing surfaces and openning connection to camera are independent processes, so you need to be sure, that they are both completed before creating CaptureSession.
Here is the example of activity to display camera preview on the screen:
public class MainActivity extends AppCompatActivity implements SurfaceHolder.Callback, Handler.Callback {
static final String TAG = "CamTest";
static final int MY_PERMISSIONS_REQUEST_CAMERA = 1242;
private static final int MSG_CAMERA_OPENED = 1;
private static final int MSG_SURFACE_READY = 2;
private final Handler mHandler = new Handler(this);
SurfaceView mSurfaceView;
SurfaceHolder mSurfaceHolder;
CameraManager mCameraManager;
String[] mCameraIDsList;
CameraDevice.StateCallback mCameraStateCB;
CameraDevice mCameraDevice;
CameraCaptureSession mCaptureSession;
boolean mSurfaceCreated = true;
boolean mIsCameraConfigured = false;
private Surface mCameraSurface = null;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
this.mSurfaceView = (SurfaceView) findViewById(R.id.SurfaceViewPreview);
this.mSurfaceHolder = this.mSurfaceView.getHolder();
this.mSurfaceHolder.addCallback(this);
this.mCameraManager = (CameraManager) this.getSystemService(Context.CAMERA_SERVICE);
try {
mCameraIDsList = this.mCameraManager.getCameraIdList();
for (String id : mCameraIDsList) {
Log.v(TAG, "CameraID: " + id);
}
} catch (CameraAccessException e) {
e.printStackTrace();
}
mCameraStateCB = new CameraDevice.StateCallback() {
@Override
public void onOpened(CameraDevice camera) {
Toast.makeText(getApplicationContext(), "onOpened", Toast.LENGTH_SHORT).show();
mCameraDevice = camera;
mHandler.sendEmptyMessage(MSG_CAMERA_OPENED);
}
@Override
public void onDisconnected(CameraDevice camera) {
Toast.makeText(getApplicationContext(), "onDisconnected", Toast.LENGTH_SHORT).show();
}
@Override
public void onError(CameraDevice camera, int error) {
Toast.makeText(getApplicationContext(), "onError", Toast.LENGTH_SHORT).show();
}
};
}
@Override
protected void onStart() {
super.onStart();
//requesting permission
int permissionCheck = ContextCompat.checkSelfPermission(this, Manifest.permission.CAMERA);
if (permissionCheck != PackageManager.PERMISSION_GRANTED) {
if (ActivityCompat.shouldShowRequestPermissionRationale(this, Manifest.permission.CAMERA)) {
} else {
ActivityCompat.requestPermissions(this, new String[]{Manifest.permission.CAMERA}, MY_PERMISSIONS_REQUEST_CAMERA);
Toast.makeText(getApplicationContext(), "request permission", Toast.LENGTH_SHORT).show();
}
} else {
Toast.makeText(getApplicationContext(), "PERMISSION_ALREADY_GRANTED", Toast.LENGTH_SHORT).show();
try {
mCameraManager.openCamera(mCameraIDsList[1], mCameraStateCB, new Handler());
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
}
@Override
protected void onStop() {
super.onStop();
try {
if (mCaptureSession != null) {
mCaptureSession.stopRepeating();
mCaptureSession.close();
mCaptureSession = null;
}
mIsCameraConfigured = false;
} catch (final CameraAccessException e) {
// Doesn't matter, cloising device anyway
e.printStackTrace();
} catch (final IllegalStateException e2) {
// Doesn't matter, cloising device anyway
e2.printStackTrace();
} finally {
if (mCameraDevice != null) {
mCameraDevice.close();
mCameraDevice = null;
mCaptureSession = null;
}
}
}
@Override
public boolean handleMessage(Message msg) {
switch (msg.what) {
case MSG_CAMERA_OPENED:
case MSG_SURFACE_READY:
// if both surface is created and camera device is opened
// - ready to set up preview and other things
if (mSurfaceCreated && (mCameraDevice != null)
&& !mIsCameraConfigured) {
configureCamera();
}
break;
}
return true;
}
private void configureCamera() {
// prepare list of surfaces to be used in capture requests
List<Surface> sfl = new ArrayList<Surface>();
sfl.add(mCameraSurface); // surface for viewfinder preview
// configure camera with all the surfaces to be ever used
try {
mCameraDevice.createCaptureSession(sfl,
new CaptureSessionListener(), null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
mIsCameraConfigured = true;
}
@Override
public void onRequestPermissionsResult(int requestCode, @NonNull String[] permissions, @NonNull int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
switch (requestCode) {
case MY_PERMISSIONS_REQUEST_CAMERA:
if (ActivityCompat.checkSelfPermission(this, Manifest.permission.CAMERA) == PackageManager.PERMISSION_GRANTED)
try {
mCameraManager.openCamera(mCameraIDsList[1], mCameraStateCB, new Handler());
} catch (CameraAccessException e) {
e.printStackTrace();
}
break;
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
mCameraSurface = holder.getSurface();
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
mCameraSurface = holder.getSurface();
mSurfaceCreated = true;
mHandler.sendEmptyMessage(MSG_SURFACE_READY);
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
mSurfaceCreated = false;
}
private class CaptureSessionListener extends
CameraCaptureSession.StateCallback {
@Override
public void onConfigureFailed(final CameraCaptureSession session) {
Log.d(TAG, "CaptureSessionConfigure failed");
}
@Override
public void onConfigured(final CameraCaptureSession session) {
Log.d(TAG, "CaptureSessionConfigure onConfigured");
mCaptureSession = session;
try {
CaptureRequest.Builder previewRequestBuilder = mCameraDevice
.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
previewRequestBuilder.addTarget(mCameraSurface);
mCaptureSession.setRepeatingRequest(previewRequestBuilder.build(),
null, null);
} catch (CameraAccessException e) {
Log.d(TAG, "setting up preview failed");
e.printStackTrace();
}
}
}
}
来源：https://stackoverflow.com/questions/39893367/how-to-show-the-camera-preview-on-a-surfaceview