我是Java和Android的新手。我正在尝试启动录制视频而不执行按钮单击。但是我收到了一个错误。
我正在尝试使用方法startCapture()，但它失败了。什么可能是错的？
错误：
java.lang.NullPointerException：尝试调用虚方法'void 关于空对象引用的android.media.MediaRecorder.start（）'
活动：
public class CameraActivity extends AppCompatActivity {
private static final String TAG = "CameraAction";
private static final int REQUEST_CAMERA_PERMISSION_RESULT = 0;
private static final int REQUEST_WRITE_EXTERNAL_STORAGE_PERMISSION_RESULT = 1;
private static final int STATE_PREVIEW = 0;
private static final int STATE_WAIT_LOCK = 1;
private int mCaptureState = STATE_PREVIEW;
private TextureView mTextureView;
private TextureView.SurfaceTextureListener mSurfaceTextureListener = 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(CameraDevice camera) {
mCameraDevice = camera;
mMediaRecorder = new MediaRecorder();
if(mIsRecording) {
try {
createVideoFileName();
} catch (IOException e) {
e.printStackTrace();
}
startRecord();
mMediaRecorder.start();
runOnUiThread(new Runnable() {
@Override
public void run() {
mChronometer.setBase(SystemClock.elapsedRealtime());
mChronometer.setVisibility(View.VISIBLE);
mChronometer.start();
}
});
} else {
startPreview();
}
}
@Override
public void onDisconnected(CameraDevice camera) {
camera.close();
mCameraDevice = null;
}
@Override
public void onError(CameraDevice camera, int error) {
camera.close();
mCameraDevice = null;
}
};
private HandlerThread mBackgroundHandlerThread;
private Handler mBackgroundHandler;
private String mCameraId;
private Size mPreviewSize;
private Size mVideoSize;
private MediaRecorder mMediaRecorder;
private Chronometer mChronometer;
private int mTotalRotation;
private CameraCaptureSession mPreviewCaptureSession;
private CameraCaptureSession.CaptureCallback mPreviewCaptureCallback = new
CameraCaptureSession.CaptureCallback() {
private void process(CaptureResult captureResult) {
switch (mCaptureState) {
case STATE_PREVIEW:
// Do nothing
break;
case STATE_WAIT_LOCK:
mCaptureState = STATE_PREVIEW;
Integer afState = captureResult.get(CaptureResult.CONTROL_AF_STATE);
if(afState == CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED ||
afState == CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED) {
Toast.makeText(getApplicationContext(), "AF Locked!", Toast.LENGTH_SHORT).show();
}
break;
}
}
@Override
public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
super.onCaptureCompleted(session, request, result);
process(result);
}
};
private CameraCaptureSession mRecordCaptureSession;
private CameraCaptureSession.CaptureCallback mRecordCaptureCallback = new
CameraCaptureSession.CaptureCallback() {
private void process(CaptureResult captureResult) {
switch (mCaptureState) {
case STATE_PREVIEW:
// Do nothing
break;
case STATE_WAIT_LOCK:
mCaptureState = STATE_PREVIEW;
Integer afState = captureResult.get(CaptureResult.CONTROL_AF_STATE);
if(afState == CaptureResult.CONTROL_AF_STATE_FOCUSED_LOCKED ||
afState == CaptureResult.CONTROL_AF_STATE_NOT_FOCUSED_LOCKED) {
Toast.makeText(getApplicationContext(), "AF Locked!", Toast.LENGTH_SHORT).show();
}
break;
}
}
@Override
public void onCaptureCompleted(CameraCaptureSession session, CaptureRequest request, TotalCaptureResult result) {
super.onCaptureCompleted(session, request, result);
process(result);
}
};
private CaptureRequest.Builder mCaptureRequestBuilder;
private Button mRecordButton;
private boolean mIsRecording = false;
private boolean mIsTimelapse = false;
private File mVideoFolder;
private String mVideoFileName;
private MainModel mainModel;
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()));
}
}
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_camera);
mainModel = (MainModel)getIntent().getSerializableExtra("serialized_data");
createVideoFolder();
mChronometer = (Chronometer) findViewById(R.id.chronometer);
mTextureView = (TextureView) findViewById(R.id.textureView);
mRecordButton = (Button) findViewById(R.id.videoButton);
mRecordButton.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (mIsRecording || mIsTimelapse) {
mChronometer.stop();
mChronometer.setVisibility(View.INVISIBLE);
mIsRecording = false;
mIsTimelapse = false;
// Starting the preview prior to stopping recording which should hopefully
// resolve issues being seen in Samsung devices.
startPreview();
mMediaRecorder.stop();
mMediaRecorder.reset();
Intent mediaStoreUpdateIntent = new Intent(Intent.ACTION_MEDIA_SCANNER_SCAN_FILE);
mediaStoreUpdateIntent.setData(Uri.fromFile(new File(mVideoFileName)));
sendBroadcast(mediaStoreUpdateIntent);
goNext();
} else {
mIsRecording = true;
checkWriteStoragePermission();
}
}
});
/*
mRecordButton.setOnLongClickListener(new View.OnLongClickListener() {
@Override
public boolean onLongClick(View v) {
mIsTimelapse =true;
checkWriteStoragePermission();
return true;
}
});
*/
}
@Override
protected void onResume() {
super.onResume();
startBackgroundThread();
if(mTextureView.isAvailable()) {
setupCamera(mTextureView.getWidth(), mTextureView.getHeight());
connectCamera();
} else {
mTextureView.setSurfaceTextureListener(mSurfaceTextureListener);
}
startCapture();
}
@Override
public void onRequestPermissionsResult(int requestCode, String[] permissions, int[] grantResults) {
super.onRequestPermissionsResult(requestCode, permissions, grantResults);
if(requestCode == REQUEST_CAMERA_PERMISSION_RESULT) {
if(grantResults[0] != PackageManager.PERMISSION_GRANTED) {
Toast.makeText(getApplicationContext(),
"Application will not run without camera services", Toast.LENGTH_SHORT).show();
}
if(grantResults[1] != PackageManager.PERMISSION_GRANTED) {
Toast.makeText(getApplicationContext(),
"Application will not have audio on record", Toast.LENGTH_SHORT).show();
}
}
if(requestCode == REQUEST_WRITE_EXTERNAL_STORAGE_PERMISSION_RESULT) {
if(grantResults[0] == PackageManager.PERMISSION_GRANTED) {
if(mIsRecording || mIsTimelapse) {
mIsRecording = true;
}
Toast.makeText(this,
"Permission successfully granted!", Toast.LENGTH_SHORT).show();
} else {
Toast.makeText(this,
"App needs to save video to run", Toast.LENGTH_SHORT).show();
}
}
}
@Override
protected void onPause() {
closeCamera();
stopBackgroundThread();
super.onPause();
}
@Override
public void onWindowFocusChanged(boolean hasFocas) {
super.onWindowFocusChanged(hasFocas);
View decorView = getWindow().getDecorView();
if(hasFocas) {
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 setupCamera(int width, int height) {
CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
for(String cameraId : cameraManager.getCameraIdList()){
CameraCharacteristics cameraCharacteristics = cameraManager.getCameraCharacteristics(cameraId);
if(cameraCharacteristics.get(CameraCharacteristics.LENS_FACING) ==
CameraCharacteristics.LENS_FACING_BACK){
continue;
}
StreamConfigurationMap map = cameraCharacteristics.get(CameraCharacteristics.SCALER_STREAM_CONFIGURATION_MAP);
int deviceOrientation = getWindowManager().getDefaultDisplay().getRotation();
mTotalRotation = sensorToDeviceRotation(cameraCharacteristics, deviceOrientation);
boolean swapRotation = mTotalRotation == 90 || mTotalRotation == 270;
int rotatedWidth = width;
int rotatedHeight = height;
if(swapRotation) {
rotatedWidth = height;
rotatedHeight = width;
}
mPreviewSize = chooseOptimalSize(map.getOutputSizes(SurfaceTexture.class), rotatedWidth, rotatedHeight);
mVideoSize = chooseOptimalSize(map.getOutputSizes(MediaRecorder.class), rotatedWidth, rotatedHeight);
mCameraId = cameraId;
return;
}
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private void startCapture() {
mIsRecording = true;
checkWriteStoragePermission();
}
private void connectCamera() {
CameraManager cameraManager = (CameraManager) getSystemService(Context.CAMERA_SERVICE);
try {
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if(ContextCompat.checkSelfPermission(this, android.Manifest.permission.CAMERA) ==
PackageManager.PERMISSION_GRANTED) {
cameraManager.openCamera(mCameraId, mCameraDeviceStateCallback, mBackgroundHandler);
} else {
if(shouldShowRequestPermissionRationale(android.Manifest.permission.CAMERA)) {
Toast.makeText(this,
"Video app required access to camera", Toast.LENGTH_SHORT).show();
}
requestPermissions(new String[] {android.Manifest.permission.CAMERA, Manifest.permission.RECORD_AUDIO
}, REQUEST_CAMERA_PERMISSION_RESULT);
}
} else {
cameraManager.openCamera(mCameraId, mCameraDeviceStateCallback, mBackgroundHandler);
}
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private void startRecord() {
try {
if(mIsRecording) {
setupMediaRecorder();
} else if(mIsTimelapse) {
setupTimelapse();
}
SurfaceTexture surfaceTexture = mTextureView.getSurfaceTexture();
surfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
Surface previewSurface = new Surface(surfaceTexture);
Surface recordSurface = mMediaRecorder.getSurface();
mCaptureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_RECORD);
mCaptureRequestBuilder.addTarget(previewSurface);
mCaptureRequestBuilder.addTarget(recordSurface);
mCameraDevice.createCaptureSession(Arrays.asList(previewSurface, recordSurface),
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(CameraCaptureSession session) {
mRecordCaptureSession = session;
try {
mRecordCaptureSession.setRepeatingRequest(
mCaptureRequestBuilder.build(), null, null
);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(CameraCaptureSession session) {
//Log.d(TAG, "onConfigureFailed: startRecord");
}
}, null);
} catch (Exception e) {
e.printStackTrace();
}
}
private void startPreview() {
SurfaceTexture surfaceTexture = mTextureView.getSurfaceTexture();
surfaceTexture.setDefaultBufferSize(mPreviewSize.getWidth(), mPreviewSize.getHeight());
Surface previewSurface = new Surface(surfaceTexture);
try {
mCaptureRequestBuilder = mCameraDevice.createCaptureRequest(CameraDevice.TEMPLATE_PREVIEW);
mCaptureRequestBuilder.addTarget(previewSurface);
mCameraDevice.createCaptureSession(Arrays.asList(previewSurface),
new CameraCaptureSession.StateCallback() {
@Override
public void onConfigured(CameraCaptureSession session) {
//Log.d(TAG, "onConfigured: startPreview");
mPreviewCaptureSession = session;
try {
mPreviewCaptureSession.setRepeatingRequest(mCaptureRequestBuilder.build(),
null, mBackgroundHandler);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
@Override
public void onConfigureFailed(CameraCaptureSession session) {
//Log.d(TAG, "onConfigureFailed: startPreview");
}
}, null);
} catch (CameraAccessException e) {
e.printStackTrace();
}
}
private void closeCamera() {
if(mCameraDevice != null) {
mCameraDevice.close();
mCameraDevice = null;
}
if(mMediaRecorder != null) {
mMediaRecorder.release();
mMediaRecorder = null;
}
}
private void startBackgroundThread() {
mBackgroundHandlerThread = new HandlerThread("Camera2VideoImage");
mBackgroundHandlerThread.start();
mBackgroundHandler = new Handler(mBackgroundHandlerThread.getLooper());
}
private void stopBackgroundThread() {
mBackgroundHandlerThread.quitSafely();
try {
mBackgroundHandlerThread.join();
mBackgroundHandlerThread = null;
mBackgroundHandler = null;
} catch (InterruptedException e) {
e.printStackTrace();
}
}
private static int sensorToDeviceRotation(CameraCharacteristics cameraCharacteristics, int deviceOrientation) {
int sensorOrienatation = cameraCharacteristics.get(CameraCharacteristics.SENSOR_ORIENTATION);
deviceOrientation = ORIENTATIONS.get(deviceOrientation);
return (sensorOrienatation + deviceOrientation + 360) % 360;
}
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, new CompareSizeByArea());
} else {
return choices[0];
}
}
private void createVideoFolder() {
File movieFile = Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_MOVIES);
mVideoFolder = new File(movieFile, "JobConvoVideos");
if(!mVideoFolder.exists()) {
mVideoFolder.mkdirs();
}
}
private File createVideoFileName() throws IOException {
String timestamp = new SimpleDateFormat("yyyyMMdd_HHmmss").format(new Date());
String prepend = "VIDEO_" + timestamp + "_";
File videoFile = File.createTempFile(prepend, ".mp4", mVideoFolder);
mVideoFileName = videoFile.getAbsolutePath();
return videoFile;
}
private void checkWriteStoragePermission() {
if(Build.VERSION.SDK_INT >= Build.VERSION_CODES.M) {
if(ContextCompat.checkSelfPermission(this, Manifest.permission.WRITE_EXTERNAL_STORAGE)
== PackageManager.PERMISSION_GRANTED) {
try {
createVideoFileName();
} catch (IOException e) {
e.printStackTrace();
}
if(mIsTimelapse || mIsRecording) {
startRecord();
mMediaRecorder.start();
mChronometer.setBase(SystemClock.elapsedRealtime());
mChronometer.setVisibility(View.VISIBLE);
mChronometer.start();
}
} else {
if(shouldShowRequestPermissionRationale(Manifest.permission.WRITE_EXTERNAL_STORAGE)) {
Toast.makeText(this, "app needs to be able to save videos", Toast.LENGTH_SHORT).show();
}
requestPermissions(new String[]{Manifest.permission.WRITE_EXTERNAL_STORAGE}, REQUEST_WRITE_EXTERNAL_STORAGE_PERMISSION_RESULT);
}
} else {
try {
createVideoFileName();
} catch (IOException e) {
e.printStackTrace();
}
if(mIsRecording || mIsTimelapse) {
startRecord();
mMediaRecorder.start();
mChronometer.setBase(SystemClock.elapsedRealtime());
mChronometer.setVisibility(View.VISIBLE);
mChronometer.start();
}
}
}
private void setupMediaRecorder() throws IOException {
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
mMediaRecorder.setAudioSource(MediaRecorder.AudioSource.MIC);
mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4);
mMediaRecorder.setOutputFile(mVideoFileName);
mMediaRecorder.setVideoEncodingBitRate(1000000);
mMediaRecorder.setVideoFrameRate(30);
mMediaRecorder.setVideoSize(mVideoSize.getWidth(), mVideoSize.getHeight());
mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
mMediaRecorder.setAudioEncoder(MediaRecorder.AudioEncoder.AAC);
mMediaRecorder.setOrientationHint(mTotalRotation);
mMediaRecorder.prepare();
}
private void setupTimelapse() throws IOException {
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.SURFACE);
mMediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_QVGA));
mMediaRecorder.setOutputFile(mVideoFileName);
mMediaRecorder.setCaptureRate(2);
mMediaRecorder.setOrientationHint(mTotalRotation);
mMediaRecorder.prepare();
}
private void goNext() {
mainModel.questions.remove(0);
if (mainModel.questions.isEmpty())
{
//END
Intent endSuccess = new Intent(this, SuccessActivity.class);
endSuccess.putExtra("serialized_data", mainModel);
startActivity(endSuccess);
}
else{
Intent goToInterview = new Intent(this, InterviewActivity.class);
goToInterview.putExtra("serialized_data", mainModel);
startActivity(goToInterview);
}
}
}
答案 0 :(得分：0)
我能够通过在onCreate方法的末尾添加这一行来实现它：mIsRecording = true;
代码
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