在我的家庭活动中单击按钮后，我试图自动在 android 设备上录制视频。
它是这样发生的：我在家庭活动中有一个按钮（激活）。单击它时，将启动新的活动视频捕获。在那个活动中，我实现了视频捕获。它在 OnClick 侦听器实现中运行良好。
但我想要的是：当活动开始时，会显示 5 秒倒计时 - 它可以在倒计时结束后开始录制，并且应该开始新的倒计时 15 秒，在此录制应该停止并进行一些处理之后. - 它不起作用。
我得到什么错误：我在 startRec() 方法的行 recorder.start() 上得到一个 nullpointerexception。
我还检查了 Log Cat，我发现就在 recorder.start() 被调用之前，我的 Recorder 是按照 Log cat 准备的。但突然它的引用变为 null。我该如何解决这个问题。如果这不是实施我的解决方案的正确方法，那可能是一种替代方法。我不希望用户单击开始和停止录制。
这是我的活动代码：
public class VideoCapture extends Activity implements OnClickListener, SurfaceHolder.Callback {
public static final String LOGTAG = "VIDEOCAPTURE";
private MediaRecorder recorder;
private SurfaceHolder holder;
private CamcorderProfile camcorderProfile;
private Camera camera;
boolean recording = false;
boolean usecamera = true;
boolean previewRunning = false;
private TextView countdown;
private TextView videotimer;
private TextView emailnotifier;
CountDownTimer videotimeremaining;
CountDownTimer initialCountDown;
String file_path;
private SharedPreferences my_prefs;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
requestWindowFeature(Window.FEATURE_NO_TITLE);
getWindow().setFlags(WindowManager.LayoutParams.FLAG_FULLSCREEN,
WindowManager.LayoutParams.FLAG_FULLSCREEN);
setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
camcorderProfile = CamcorderProfile.get(CamcorderProfile.QUALITY_LOW);
my_prefs = PreferenceManager.getDefaultSharedPreferences(this);
setContentView(R.layout.activity_video);
countdown = (TextView)findViewById(R.id.countdown);
videotimer = (TextView)findViewById(R.id.video_timer);
emailnotifier = (TextView) findViewById(R.id.emailtextview);
int CD = 4; // Count Down
SurfaceView cameraView = (SurfaceView) findViewById(R.id.CameraView);
holder = cameraView.getHolder();
holder.addCallback(this);
holder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
initialCountDown = new CountDownTimer(4000, 1000) {
public void onTick(long millisUntilFinished) {
countdown.setText("" + millisUntilFinished / 1000);
}
public void onFinish() {
countdown.setVisibility(View.GONE);
videotimeremaining.start();
changeRecordingStatus();
}
}.start();
videotimeremaining = new CountDownTimer(15000, 1000) {
public void onTick(long millisUntilFinished) {
videotimer.setText("00:" + millisUntilFinished / 1000);
}
public void onFinish() {
videotimer.setVisibility(View.GONE);
changeRecordingStatus();
}
};
cameraView.setClickable(false);
//cameraView.setOnClickListener(this);
}
private void changeRecordingStatus(){
if(!recording)
startRec();
else
stopRec();
}
public void prepareRecorder() {
recorder = new MediaRecorder();
recorder.setPreviewDisplay(holder.getSurface());
if (usecamera) {
camera.unlock();
recorder.setCamera(camera);
Log.i(LOGTAG, "recorder is set");
}
recorder.setAudioSource(MediaRecorder.AudioSource.DEFAULT);
recorder.setVideoSource(MediaRecorder.VideoSource.DEFAULT);
recorder.setProfile(camcorderProfile);
File dir = new File("/sdcard/PanicButton/");
if(!dir.exists()){
dir.mkdir();
}
// This is all very sloppy
if (camcorderProfile.fileFormat == MediaRecorder.OutputFormat.THREE_GPP) {
try {
File newFile = File.createTempFile("/PanicButton/", ".3gp", Environment.getExternalStorageDirectory());
recorder.setOutputFile(newFile.getAbsolutePath());
file_path = newFile.getAbsolutePath().toString();
}catch (IOException e) {
Log.v(LOGTAG,"Couldn't create file");
e.printStackTrace();
finish();
}
}else {
try {
File newFile = File.createTempFile("/PanicButton/", ".mp4", Environment.getExternalStorageDirectory());
recorder.setOutputFile(newFile.getAbsolutePath());
file_path = newFile.getAbsolutePath().toString();
}catch (Exception e) {
Log.v(LOGTAG,"Couldn't create file");
e.printStackTrace();
finish();
}
}
recorder.setMaxDuration(15000); // 15 seconds
//recorder.setMaxFileSize(5000000); // Approximately 5 megabytes
try {
recorder.prepare();
Log.i(LOGTAG, "Recorder Prepared");
}catch (IllegalStateException e) {
e.printStackTrace();
finish();
} catch (IOException e) {
e.printStackTrace();
finish();
}
}
public void startRec(){
recording = true;
recorder.start();
Log.v(LOGTAG, "Recording Started");
}
public void stopRec(){
if (recording) {
recorder.stop();
if (usecamera) {
try {
camera.reconnect();
} catch (IOException e) {
e.printStackTrace();
}
}
// recorder.release();
recording = false;
Log.v(LOGTAG, "Recording Stopped");
//Toast.makeText(this, "Video Is Ready To Be Sent", Toast.LENGTH_SHORT).show();
//Testing emails
if (android.os.Build.VERSION.SDK_INT > 9) {
StrictMode.ThreadPolicy policy =
new StrictMode.ThreadPolicy.Builder().permitAll().build();
StrictMode.setThreadPolicy(policy);
}
// Let's prepareRecorder so we can record again
prepareRecorder();
}
}
public void surfaceCreated(SurfaceHolder holder) {
Log.v(LOGTAG, "surfaceCreated");
if (usecamera) {
camera = Camera.open();
Log.i(LOGTAG, "Camera is set");
try {
camera.setPreviewDisplay(holder);
camera.startPreview();
previewRunning = true;
Log.i(LOGTAG, "Camera preview is running");
}
catch (IOException e) {
Log.e(LOGTAG,e.getMessage());
e.printStackTrace();
}
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width, int height) {
Log.v(LOGTAG, "surfaceChanged");
if (!recording && usecamera) {
if (previewRunning){
camera.stopPreview();
Log.i(LOGTAG, "Camera preview stopped");
}
try {
Camera.Parameters p = camera.getParameters();
p.setPreviewSize(camcorderProfile.videoFrameWidth, camcorderProfile.videoFrameHeight);
p.setPreviewFrameRate(camcorderProfile.videoFrameRate);
camera.setParameters(p);
camera.setPreviewDisplay(holder);
camera.startPreview();
previewRunning = true;
Log.i(LOGTAG, "Camera preview running with parameteres set");
}
catch (IOException e) {
Log.e(LOGTAG,e.getMessage());
e.printStackTrace();
}
prepareRecorder();
}
}
public void surfaceDestroyed(SurfaceHolder holder) {
Log.v(LOGTAG, "surfaceDestroyed");
if (recording) {
recorder.stop();
recording = false;
}
recorder.release();
if (usecamera) {
previewRunning = false;
//camera.lock();
camera.release();
}
finish();
}
}