我在Android应用程序中使用相机拍摄照片和视频。我正在使用以下代码，但它强制关闭应用程序。 LogCat和代码如下所示。如果有人可以提供帮助，我们将非常感激。
logcat的：
09-09 14:32:08.246: E/AndroidRuntime(4764): FATAL EXCEPTION: main
09-09 14:32:08.246: E/AndroidRuntime(4764): java.lang.NullPointerException
09-09 14:32:08.246: E/AndroidRuntime(4764): at com.example.cameravideo.VideoCaptureActivity.initRecorder(VideoCaptureActivity.java:72)
09-09 14:32:08.246: E/AndroidRuntime(4764): at com.example.cameravideo.VideoCaptureActivity.surfaceCreated(VideoCaptureActivity.java:100)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.SurfaceView.updateWindow(SurfaceView.java:571)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.SurfaceView.access$000(SurfaceView.java:86)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.SurfaceView$3.onPreDraw(SurfaceView.java:175)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.ViewTreeObserver.dispatchOnPreDraw(ViewTreeObserver.java:833)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1860)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1004)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:5481)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.Choreographer$CallbackRecord.run(Choreographer.java:749)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.Choreographer.doCallbacks(Choreographer.java:562)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.Choreographer.doFrame(Choreographer.java:532)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:735)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.os.Handler.handleCallback(Handler.java:730)
09-09 14:32:08.246: E/AndroidRuntime(4764): at android.os.Handler.dispatchMessage(Handler.java:92)
代码：
public class VideoCaptureActivity extends Activity implements
SurfaceHolder.Callback {
private final String VIDEO_PATH_NAME = "/mnt/sdcard/VGA_30fps_512vbrate.mp4";
private MediaRecorder mMediaRecorder;
private Camera mCamera;
private SurfaceView mSurfaceView;
private SurfaceHolder mHolder;
private View mToggleButton;
private boolean mInitSuccesful;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main); setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_LANDSCAPE);
mSurfaceView = (SurfaceView) findViewById(R.id.surface_camera);
mHolder = mSurfaceView.getHolder();
mHolder.addCallback(this);
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
mToggleButton = (ToggleButton) findViewById(R.id.toggleButton);
mToggleButton.setOnClickListener(new OnClickListener()
{
public void onClick(View v) {
if (((ToggleButton) v).isChecked()) {
mMediaRecorder.start();
try {
Thread.sleep(10 * 1000);
}
catch (Exception e) {
e.printStackTrace();
}
finish();
}
else {
mMediaRecorder.stop();
mMediaRecorder.reset();
try {
initRecorder(mHolder.getSurface());
}
catch (IOException e) {
e.printStackTrace();
}
}
}
});
}
private void initRecorder(Surface surface) throws IOException {
if (mCamera == null) {
mCamera = Camera.open();
mCamera.unlock();
}
if (mMediaRecorder == null)
mMediaRecorder = new MediaRecorder();
mMediaRecorder.setPreviewDisplay(surface);
mMediaRecorder.setCamera(mCamera);
mMediaRecorder.setVideoSource(MediaRecorder.VideoSource.DEFAULT);
mMediaRecorder.setOutputFormat(MediaRecorder.OutputFormat.MPEG_4); mMediaRecorder.setVideoEncoder(MediaRecorder.VideoEncoder.H264);
mMediaRecorder.setVideoEncodingBitRate(512 * 1000);
mMediaRecorder.setVideoFrameRate(30);
mMediaRecorder.setVideoSize(640, 480);
mMediaRecorder.setOutputFile(VIDEO_PATH_NAME);
try {
mMediaRecorder.prepare();
}
catch (IllegalStateException e) {
e.printStackTrace();
}
mInitSuccesful = true;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
try {
if (!mInitSuccesful)
initRecorder(mHolder.getSurface());
}
catch (IOException e) {
e.printStackTrace();
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
shutdown();
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {
}
private void shutdown() {
mMediaRecorder.reset();
mMediaRecorder.release();
mCamera.release();
mMediaRecorder = null;
mCamera = null;
}
}
答案 0 :(得分：0)
异常的原因可能是因为Camera.open（）返回null！
if (mCamera == null) {
mCamera = Camera.open();
mCamera.unlock();
}
您的清单文件中是否包含以下内容？
<uses-permission android:name="android.permission.CAMERA" />
<uses-feature android:name="android.hardware.camera" />
如果您的api级别＆gt; = 2.3
，请尝试使用Camera.open(int cameraId);
答案 1 :(得分：0)
尝试下面的代码，了解手机上有哪些CameraId可用，然后使用Id中的Camera.open(id)之一
private void knowIfCameraIsAvailable() {
int camNumber = Camera.getNumberOfCameras();
System.out.println("Number of Camera = " + camNumber);
for (int i = 0; i < camNumber; i++) {
try {
Log.e("Camera ID", "ID == " + i);
Camera cam = Camera.open(i);
System.out.println("Camera object = " + cam);
Camera.Parameters camParameter = cam.getParameters();
System.out.println("camParameter.getMaxZoom() = "
+ camParameter.getMaxZoom());
cam.unlock();
cam.release();
} catch (NullPointerException e) {
Log.i("NullPointer", "Object NULL");
e.printStackTrace();
} catch (IllegalStateException e) {
Log.i("IllegalState", "Illegal State");
e.printStackTrace();
} catch (Exception e) {
Log.i("Exception", "Other Exception");
e.printStackTrace();
}
}
}