当我单击一个按钮以启动活动时，会出现以下错误：
很遗憾，appName已停止。
我有以下CameraActivity.java文件：
public class CameraActivity extends Activity{
// LogCat tag
private static final String TAG = CameraActivity.class.getSimpleName();
// Camera activity request codes
private static final int CAMERA_CAPTURE_IMAGE_REQUEST_CODE = 100;
private static final int CAMERA_CAPTURE_VIDEO_REQUEST_CODE = 200;
public static final int MEDIA_TYPE_IMAGE = 1;
public static final int MEDIA_TYPE_VIDEO = 2;
private Uri fileUri; // file url to store image/video
private Button btnCapturePicture, btnRecordVideo;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.camera_main);
btnCapturePicture = (Button) findViewById(R.id.btnCapturePicture);
btnRecordVideo = (Button) findViewById(R.id.btnRecordVideo);
/**
* Capture image button click event
*/
btnCapturePicture.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// capture picture
captureImage();
}
});
/**
* Record video button click event
*/
btnRecordVideo.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
// record video
recordVideo();
}
});
// Checking camera availability
if (!isDeviceSupportCamera()) {
Toast.makeText(getApplicationContext(),
"Sorry! Your device doesn't support camera",
Toast.LENGTH_LONG).show();
// will close the app if the device does't have camera
finish();
}
}
/**
* Checking device has camera hardware or not
* */
private boolean isDeviceSupportCamera() {
if (getApplicationContext().getPackageManager().hasSystemFeature(
PackageManager.FEATURE_CAMERA)) {
// this device has a camera
return true;
} else {
// no camera on this device
return false;
}
}
public void goBack(View view) {
Intent intent = new Intent(this, IncidentMenuActivity.class);
startActivity(intent);
}
/**
* Launching camera app to capture image
*/
private void captureImage() {
Intent intent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
fileUri = getOutputMediaFileUri(MEDIA_TYPE_IMAGE);
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri);
// start the image capture Intent
startActivityForResult(intent, CAMERA_CAPTURE_IMAGE_REQUEST_CODE);
}
/**
* Launching camera app to record video
*/
private void recordVideo() {
Intent intent = new Intent(MediaStore.ACTION_VIDEO_CAPTURE);
fileUri = getOutputMediaFileUri(MEDIA_TYPE_VIDEO);
// set video quality
intent.putExtra(MediaStore.EXTRA_VIDEO_QUALITY, 1);
intent.putExtra(MediaStore.EXTRA_OUTPUT, fileUri); // set the image file
// name
// start the video capture Intent
startActivityForResult(intent, CAMERA_CAPTURE_VIDEO_REQUEST_CODE);
}
/**
* Here we store the file url as it will be null after returning from camera
* app
*/
@Override
protected void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
// save file url in bundle as it will be null on screen orientation
// changes
outState.putParcelable("file_uri", fileUri);
}
@Override
protected void onRestoreInstanceState(Bundle savedInstanceState) {
super.onRestoreInstanceState(savedInstanceState);
// get the file url
fileUri = savedInstanceState.getParcelable("file_uri");
}
/**
* Receiving activity result method will be called after closing the camera
* */
@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
// if the result is capturing Image
if (requestCode == CAMERA_CAPTURE_IMAGE_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
// successfully captured the image
// launching upload activity
launchUploadActivity(true);
} else if (resultCode == RESULT_CANCELED) {
// user cancelled Image capture
Toast.makeText(getApplicationContext(),
"User cancelled image capture", Toast.LENGTH_SHORT)
.show();
} else {
// failed to capture image
Toast.makeText(getApplicationContext(),
"Sorry! Failed to capture image", Toast.LENGTH_SHORT)
.show();
}
} else if (requestCode == CAMERA_CAPTURE_VIDEO_REQUEST_CODE) {
if (resultCode == RESULT_OK) {
// video successfully recorded
// launching upload activity
launchUploadActivity(false);
} else if (resultCode == RESULT_CANCELED) {
// user cancelled recording
Toast.makeText(getApplicationContext(),
"User cancelled video recording", Toast.LENGTH_SHORT)
.show();
} else {
// failed to record video
Toast.makeText(getApplicationContext(),
"Sorry! Failed to record video", Toast.LENGTH_SHORT)
.show();
}
}
}
private void launchUploadActivity(boolean isImage){
Intent i = new Intent(CameraActivity.this, UploadActivity.class);
i.putExtra("filePath", fileUri.getPath());
i.putExtra("isImage", isImage);
startActivity(i);
}
/**
* ------------ Helper Methods ----------------------
* */
/**
* Creating file uri to store image/video
*/
public Uri getOutputMediaFileUri(int type) {
return Uri.fromFile(getOutputMediaFile(type));
}
/**
* returning image / video
*/
private static File getOutputMediaFile(int type) {
// External sdcard location
File mediaStorageDir = new File(
Environment
.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES),
Config.IMAGE_DIRECTORY_NAME);
// Create the storage directory if it does not exist
if (!mediaStorageDir.exists()) {
if (!mediaStorageDir.mkdirs()) {
Log.d(TAG, "Oops! Failed create "
+ Config.IMAGE_DIRECTORY_NAME + " directory");
return null;
}
}
// Create a media file name
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss",
Locale.getDefault()).format(new Date());
File mediaFile;
if (type == MEDIA_TYPE_IMAGE) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "IMG_" + timeStamp + ".jpg");
} else if (type == MEDIA_TYPE_VIDEO) {
mediaFile = new File(mediaStorageDir.getPath() + File.separator
+ "VID_" + timeStamp + ".mp4");
} else {
return null;
}
return mediaFile;
}
}
在我的logCat中，出现以下错误：
01-01 22:12:30.280 19343-19343/com.example.infonet.emonitor E/AndroidRuntime: FATAL EXCEPTION: main
java.lang.NullPointerException: file
at android.net.Uri.fromFile(Uri.java:444)
at com.example.infonet.emonitor.CameraActivity.getOutputMediaFileUri(CameraActivity.java:230)
at com.example.infonet.emonitor.CameraActivity.captureImage(CameraActivity.java:115)
at com.example.infonet.emonitor.CameraActivity.access$000(CameraActivity.java:20)
at com.example.infonet.emonitor.CameraActivity$1.onClick(CameraActivity.java:64)
at android.view.View.performClick(View.java:4204)
at android.view.View$PerformClick.run(View.java:17355)
at android.os.Handler.handleCallback(Handler.java:725)
at android.os.Handler.dispatchMessage(Handler.java:92)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:5041)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:793)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:560)
at dalvik.system.NativeStart.main(Native Method)
01-01 22:12:31.490 648-734/? E/SurfaceFlinger: ro.sf.lcd_density must be defined as a build property
我无法指出可能出什么问题了，因为我还没有扎根android，而对这些错误的理解对我来说是不理解的。