所以我是编码和使用相机的新手。我不明白为什么cameraId是null。如果有人可以帮助我，真的很感激。谢谢
代码：
public class CameraFragment extends Fragment {
private TextureView textureView;
private HandlerThread mBackgroundHandlerThread;
private Handler mBackgroundHandler;
private String mCameraId;
private Size mPreviewSize;
public static CameraFragment newInstance() {
return new CameraFragment();
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
View rootView = inflater.inflate(R.layout. fragment_camera, container, false);
textureView = (TextureView) rootView.findViewById(R.id.textureView);
return rootView;
}
private static final int REQUEST_CAMERA_PERMISSION_RESULT = 0;
private TextureView.SurfaceTextureListener surfaceTextureListener = new TextureView.SurfaceTextureListener() {
@Override
public void onSurfaceTextureAvailable(SurfaceTexture surface, int width, int height) {
setupCamera(width, height);
connectCamera();
}
@Override
public void onSurfaceTextureSizeChanged(SurfaceTexture surface, int width, int height) {
}
@Override
public boolean onSurfaceTextureDestroyed(SurfaceTexture surface) {
return false;
}
@Override
public void onSurfaceTextureUpdated(SurfaceTexture surface) {
}
};
private CameraDevice mCameraDevice;
private CameraDevice.StateCallback mCameraDeviceStateCallback = new CameraDevice.StateCallback() {
@Override
public void onOpened(@NonNull CameraDevice camera) {
mCameraDevice = camera;
startPreview();
//Toast.makeText(getApplicationContext(), "Camera connected!", Toast.LENGTH_LONG).show();
}
@Override
public void onDisconnected(@NonNull CameraDevice camera) {
camera.close();
mCameraDevice = null;
}
@Override
public void onError(@NonNull CameraDevice camera, int error) {
camera.close();
mCameraDevice = null;
}
};
@Override
public void onResume() {
super.onResume();
startBackgroundThread();
if (textureView.isAvailable()) {
//setupCamera(textureView.getWidth(), textureView.getHeight());
connectCamera();
} else {
textureView.setSurfaceTextureListener(surfaceTextureListener);
}
}
@Override
public void onPause() {
closeCamera();
stopBackgroundThread();
super.onPause();
}
private void closeCamera() {
if(mCameraDevice != null) {
mCameraDevice.close();
mCameraDevice = null;
}
}
private void stopBackgroundThread() {
mBackgroundHandlerThread.quitSafely();
try {
mBackgroundHandlerThread.join();
mBackgroundHandlerThread = null;
mBackgroundHandler = null;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private void setupCamera(int width, int height) {
if(mCameraDevice == null)
return;
CameraManager cameraManager = (CameraManager) getActivity().getSystemService(Context.CAMERA_SERVICE);
try {
if (cameraManager != null) {
mCameraId = cameraManager.getCameraIdList()[0];
}
assert cameraManager != null;
for (String cameraId : cameraManager.getCameraIdList()) {
CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraId);
if(cameraCharacteristics.get(CameraCharacteristics.LENS_FACING) ==
CameraCharacteristics.LENS_FACING_FRONT){
continue;
}
StreamConfigurationMap map = cameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
int deviceOrientation = getActivity().getWindowManager().getDefaultDisplay().getRotation();
int totalRotation = sensorToDeviceRotation(cameraCharacteristics, deviceOrientation);
boolean swapRotation = totalRotation == 90 || totalRotation == 270;
int rotatedWidth = width;
int rotatedHeight = height;
if (swapRotation){
rotatedWidth = height;
rotatedHeight = width;
}
if (map != null) {
mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class), rotatedWidth, rotatedHeight);
}
mCameraId = cameraId;
return;
}
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private void connectCamera() {
CameraManager cameraManager = (CameraManager) getActivity().getSystemService(Context.CAMERA_SERVICE);
try {
if (Build.VERSION.SDK_INT <= Build.VERSION_CODES.M) {
if (ContextCompat.checkSelfPermission(getActivity(), Manifest.permission.CAMERA) ==
PackageManager.PERMISSION_GRANTED) {
assert cameraManager != null;
cameraManager.openCamera(mCameraId, mCameraDeviceStateCallback, mBackgroundHandler);
} else {
if (shouldShowRequestPermissionRationale(Manifest.permission.CAMERA)) {
Toast.makeText(getActivity(), "This app requires access to camera", Toast.LENGTH_LONG).show();
}
requestPermissions(new String[]{Manifest.permission.CAMERA}, REQUEST_CAMERA_PERMISSION_RESULT);
}
} else {
assert cameraManager != null;
cameraManager.openCamera(mCameraId, mCameraDeviceStateCallback, mBackgroundHandler);
}
}catch(CameraAccessException e){
e.printStackTrace();
}
}
private CaptureRequest.Builder mCaptureRequestBuilder;
private static SparseIntArray ORIENTATIONS = new SparseIntArray();
static {
ORIENTATIONS.append(Surface.ROTATION_0, 0);
ORIENTATIONS.append(Surface.ROTATION_90, 90);
ORIENTATIONS.append(Surface.ROTATION_180, 180);
ORIENTATIONS.append(Surface.ROTATION_270, 270);
}
private static class CompareSizeByArea implements Comparator<Size> {
@Override
public int compare(Size lhs, Size rhs){
return Long.signum((long) lhs.getWidth() * lhs.getHeight() /
(long) rhs.getWidth() * rhs.getHeight());
}
}
private static int sensorToDeviceRotation(CameraCharacteristics cameraCharacteristics, int deviceOrientation){
int sensorOrientation = cameraCharacteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
deviceOrientation = ORIENTATIONS.get(deviceOrientation);
return(sensorOrientation + deviceOrientation + 360) % 360;
}
public void onWindowFocusChanged (boolean hasFocus) {
super.getActivity().onWindowFocusChanged(hasFocus);
View decorView = getActivity().getWindow().getDecorView();
if(hasFocus){
decorView.setSystemUiVisibility(View.SYSTEM_UI_FLAG_LAYOUT_STABLE
| View.SYSTEM_UI_FLAG_IMMERSIVE_STICKY
| View.SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN
| View.SYSTEM_UI_FLAG_LAYOUT_HIDE_NAVIGATION
| View.SYSTEM_UI_FLAG_FULLSCREEN
| View.SYSTEM_UI_FLAG_HIDE_NAVIGATION);
}
}
private void startBackgroundThread() {
mBackgroundHandlerThread = new HandlerThread("Camera Background");
mBackgroundHandlerThread.start();
mBackgroundHandler = new Handler(mBackgroundHandlerThread.getLooper());
}
private void startPreview() {
SurfaceTexture surfaceTexture = textureView.getSurfaceTexture();
assert surfaceTexture != null;
surfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
Surface previewSurface = new Surface(surfaceTexture);
try {
mCaptureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mCaptureRequestBuilder.addTarget(previewSurface);
mCameraDevice.createCaptureSession(Collections.singletonList(previewSurface),
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(@NonNull CameraCaptureSession session) {
try {
session.setRepeatingRequest(mCaptureRequestBuilder.build(),
null, mBackgroundHandler);
} catch (CameraAccessException e){
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(@NonNull CameraCaptureSession session) {
Toast.makeText(getActivity(), "Unable to connect to camera", Toast.LENGTH_LONG).show();
}
}, null);
} catch (CameraAccessException e){
e.printStackTrace();
}
}
private static Size chooseOptimalSize(Size[] choices, int width, int height) {
List<Size> bigEnough = new ArrayList<Size>();
for(Size option : choices){
if(option.getHeight() == option.getWidth() * height/width &&
option.getWidth() >= width && option.getHeight() >= height) {
bigEnough.add(option);
}
}
if(bigEnough.size() > 0){
return Collections.min(bigEnough, (Comparator<? super Size>) new CompareSizeByArea());
} else {
return choices[0];
}
}
}
日志：
> FATAL EXCEPTION: main
Process: com.example.patrick.wz, PID: 5246
java.lang.IllegalArgumentException: cameraId was null
at android.hardware.camera2.CameraManager.openCameraForUid(CameraManager.java:454)
at android.hardware.camera2.CameraManager.openCamera(CameraManager.java:430)
at com.example.patrick.wz.Fragments.CameraFragment.connectCamera(CameraFragment.java:214)
at com.example.patrick.wz.Fragments.CameraFragment.access$100(CameraFragment.java:40)
at com.example.patrick.wz.Fragments.CameraFragment$1.onSurfaceTextureAvailable(CameraFragment.java:74)
at android.view.TextureView.getHardwareLayer(TextureView.java:390)
at android.view.TextureView.draw(TextureView.java:339)
at android.view.View.updateDisplayListIfDirty(View.java:18069)
at android.view.View.draw(View.java:18847)
at android.view.ViewGroup.drawChild(ViewGroup.java:4214)
at android.view.ViewGroup.dispatchDraw(ViewGroup.java:4000)
at android.view.View.updateDisplayListIfDirty(View.java:18060)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ViewGroup.recreateChildDisplayList(ViewGroup.java:4198)
at android.view.ViewGroup.dispatchGetDisplayList(ViewGroup.java:4178)
at android.view.View.updateDisplayListIfDirty(View.java:18028)
at android.view.ThreadedRenderer.updateRootDisplayList(ThreadedRenderer.java:659)
at android.view.ThreadedRenderer.draw(ThreadedRenderer.java:757)
at android.view.ViewRootImpl.draw(ViewRootImpl.java:2980)
at android.view.ViewRootImpl.performDraw(ViewRootImpl.java:2794)
at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:2347)
at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1386)
at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:6733)
at android.view.Choreographer$CallbackRecord.run(Choreographer.java:911)
at android.view.Choreographer.doCallbacks(Choreographer.java:723)
at android.view.Choreographer.doFrame(Choreographer.java:658)
at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:897)
at android.os.Handler.handleCallback(Handler.java:789)
at android.os.Handler.dispatchMessage(Handler.java:98)
答案 0 :(得分：0)
在onResume中，你已经注释掉了对setupCamera的调用，这就是mCameraId的设置。所以当你进入connectCamera时它仍然是空的。