试图将摄像头切换回前面，但出现异常。找不到问题请检查并帮助..
error:- 01-27 11:49:00.376: E/AndroidRuntime(30767): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vdrecord/com.vdrecord.AndroidVideoCapture}: java.lang.NullPointerException
我的代码：-
public class AndroidVideoCapture extends Activity{
private static final String TAG = "CameraRecorderActivity";
private Camera myCamera;
private MyCameraSurfaceView myCameraSurfaceView;
private MediaRecorder mediaRecorder;
private static String val="yes";
private Button useOtherCamera;
Button myButton;
SurfaceHolder surfaceHolder;
boolean recording;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
recording = false;
setContentView(R.layout.activity_android_video_capture);
useOtherCamera = (Button) findViewById(R.id.useOtherCamera);
useOtherCamera.setOnClickListener(
new View.OnClickListener() {
@Override
public void onClick(View v) {
//Get Camera for preview
myCamera = getCameraInstance();
}
});
FrameLayout myCameraPreview = (FrameLayout)findViewById(R.id.videoview);
myCameraPreview.addView(myCameraSurfaceView);
myButton = (Button)findViewById(R.id.mybutton);
myButton.setOnClickListener(myButtonOnClickListener);
myButton.setOnClickListener(myButtonOnClickListener);
if(myCamera == null){
System.out.println("PRINT TRACK--7 ");
Toast.makeText(AndroidVideoCapture.this,
"Fail to get Camera",
Toast.LENGTH_LONG).show();
}
myCameraSurfaceView = new MyCameraSurfaceView(this, myCamera);
}
Button.OnClickListener myButtonOnClickListener
= new Button.OnClickListener(){
@Override
public void onClick(View v) {
// TODO Auto-generated method stub
if(recording){
// stop recording and release camera
mediaRecorder.stop(); // stop the recording
releaseMediaRecorder(); // release the MediaRecorder object
//Exit after saved
finish();
}else{
//Release Camera before MediaRecorder start
releaseCamera();
if(!prepareMediaRecorder()){
Toast.makeText(AndroidVideoCapture.this,
"Fail in prepareMediaRecorder()!\n - Ended -",
Toast.LENGTH_LONG).show();
finish();
}
mediaRecorder.start();
recording = true;
myButton.setText("STOP");
}
}};
public int getFrontCameraId() {
CameraInfo ci = new CameraInfo();
for (int i = 0 ; i < Camera.getNumberOfCameras(); i++) {
Camera.getCameraInfo(i, ci);
if ((val=="yes") && (ci.facing == CameraInfo.CAMERA_FACING_FRONT))
{
val="no";
return i;
}
}
return CameraInfo.CAMERA_FACING_BACK; // No front-facing camera found
}
public Camera getCameraInstance(){
// TODO Auto-generated method stub
Camera c = null;
try {
int index = getFrontCameraId();
if (index != -1)
{
c = Camera.open(index);
// c = Camera.open(); // attempt to get a Camera instance
}else{
c = Camera.open(index);
}
}
catch (Exception e){
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
// Camera is not available (in use or does not exist)
}
return c; // returns null if camera is unavailable
}
private boolean prepareMediaRecorder(){
myCamera = getCameraInstance();
mediaRecorder = new MediaRecorder();
myCamera.unlock();
mediaRecorder.setCamera(myCamera);
mediaRecorder.setAudioSource(MediaRecorder.AudioSource.CAMCORDER);
mediaRecorder.setVideoSource(MediaRecorder.VideoSource.CAMERA);
mediaRecorder.setProfile(CamcorderProfile.get(CamcorderProfile.QUALITY_LOW));
mediaRecorder.setOutputFile("/sdcard/myvideo.mp4");
mediaRecorder.setMaxDuration(60000); // Set max duration 60 sec.
mediaRecorder.setMaxFileSize(5000000); // Set max file size 5M
mediaRecorder.setPreviewDisplay(myCameraSurfaceView.getHolder().getSurface());
try {
mediaRecorder.prepare();
} catch (IllegalStateException e) {
releaseMediaRecorder();
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
return false;
} catch (IOException e) {
releaseMediaRecorder();
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
return false;
}
return true;
}
@Override
protected void onPause() {
super.onPause();
releaseMediaRecorder(); // if you are using MediaRecorder, release it first
releaseCamera(); // release the camera immediately on pause event
}
private void releaseMediaRecorder(){
if (mediaRecorder != null) {
mediaRecorder.reset(); // clear recorder configuration
mediaRecorder.release(); // release the recorder object
mediaRecorder = null;
myCamera.lock(); // lock camera for later use
}
}
private void releaseCamera(){
if (myCamera != null){
myCamera.release(); // release the camera for other applications
myCamera = null;
}
}
public class MyCameraSurfaceView extends SurfaceView implements SurfaceHolder.Callback{
private SurfaceHolder mHolder;
private Camera mCamera;
public MyCameraSurfaceView(Context context, Camera camera) {
super(context);
mCamera = camera;
// Install a SurfaceHolder.Callback so we get notified when the
// underlying surface is created and destroyed.
mHolder = getHolder();
mHolder.addCallback(this);
// deprecated setting, but required on Android versions prior to 3.0
mHolder.setType(SurfaceHolder.SURFACE_TYPE_PUSH_BUFFERS);
}
@Override
public void surfaceChanged(SurfaceHolder holder, int format, int weight,
int height) {
// If your preview can change or rotate, take care of those events here.
// Make sure to stop the preview before resizing or reformatting it.
if (mHolder.getSurface() == null){
// preview surface does not exist
return;
}
// stop preview before making changes
try {
mCamera.stopPreview();
} catch (Exception e){
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
// ignore: tried to stop a non-existent preview
}
// make any resize, rotate or reformatting changes here
// start preview with new settings
try {
mCamera.setPreviewDisplay(mHolder);
mCamera.startPreview();
} catch (Exception e){
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
// The Surface has been created, now tell the camera where to draw the preview.
try {
mCamera.setPreviewDisplay(holder);
mCamera.startPreview();
} catch (IOException e) {
Log.d(TAG, "Error setting camera preview: " + e.getMessage());
}
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
}
}
}
Error Log:- 01-27 11:49:00.376: E/AndroidRuntime(30767): FATAL EXCEPTION: main 01-27 11:49:00.376: E/AndroidRuntime(30767): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.vdrecord/com.vdrecord.AndroidVideoCapture}: java.lang.NullPointerException 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1968) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1993) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.ActivityThread.access$600(ActivityThread.java:127) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1159) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.os.Handler.dispatchMessage(Handler.java:99) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.os.Looper.loop(Looper.java:137) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.ActivityThread.main(ActivityThread.java:4507) 01-27 11:49:00.376: E/AndroidRuntime(30767): at java.lang.reflect.Method.invokeNative(Native Method) 01-27 11:49:00.376: E/AndroidRuntime(30767): at java.lang.reflect.Method.invoke(Method.java:511) 01-27 11:49:00.376: E/AndroidRuntime(30767): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:980) 01-27 11:49:00.376: E/AndroidRuntime(30767): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:747) 01-27 11:49:00.376: E/AndroidRuntime(30767): at dalvik.system.NativeStart.main(Native Method) 01-27 11:49:00.376: E/AndroidRuntime(30767): Caused by: java.lang.NullPointerException 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.view.ViewGroup.addView(ViewGroup.java:3158) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.view.ViewGroup.addView(ViewGroup.java:3145) 01-27 11:49:00.376: E/AndroidRuntime(30767): at com.vdrecord.AndroidVideoCapture.onCreate(AndroidVideoCapture.java:51) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.Activity.performCreate(Activity.java:4465) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1052) 01-27 11:49:00.376: E/AndroidRuntime(30767): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1932)