personne3000 personne3000 - 3 months ago 31
Android Question

Picture file captured with camera intent empty for a while in onActivityResult

I am having a very strange bug trying to take a picture via intent.
Activity code (a little simplified):

private void startCapture() throws IOException {
// Create output file
final File photoFile = makePhotoFile();
_photoPath = photoFile.getAbsolutePath();

Intent cameraIntent = new Intent(MediaStore.ACTION_IMAGE_CAPTURE);
/* IMPORTANT NOTE TO READERS
* As of Android N (which went out shortly after I posted this question),
* you cannot use Uri.fromFile this way anymore.
* You should use a FileProvider. */
cameraIntent.putExtra(MediaStore.EXTRA_OUTPUT, Uri.fromFile(photoFile));

if (cameraIntent.resolveActivity(getPackageManager()) != null) {
startActivityForResult(cameraIntent, REQUEST_CODE_IMAGE_CAPTURE);
}
else {
deleteCurrentPhoto();
}
}

private File makePhotoFile() throws IOException {
String timeStamp = new SimpleDateFormat("yyyyMMdd_HHmmss", Locale.ENGLISH).format(new Date());
String imageFileName = "MyPhoto_" + timeStamp + "_";
File storageDir = getExternalFilesDir(Environment.DIRECTORY_PICTURES);
return File.createTempFile(imageFileName, ".jpg", storageDir);
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
super.onActivityResult(requestCode, resultCode, data);

if(requestCode == REQUEST_CODE_IMAGE_CAPTURE) {
if(resultCode == RESULT_OK) {
ByteArrayOutputStream bos = new ByteArrayOutputStream();
final byte[] buffer = new byte[2048];
int read;
byte[] photoBytes;
try(FileInputStream fis = new FileInputStream(_photoPath)) {

for(int i=0; i<10; i++) { // Always working after first iteration though
if( (read = fis.read(buffer)) <= 0) {
// Why does this get printed once ??
Log.w("my.package.my.app", "Empty for now...");
}
else {
Log.w("my.package.my.app", "Working now !");
bos.write(buffer, 0, read);
break;
}
}

while((read = fis.read(buffer)) >= 0) {
bos.write(buffer, 0, read);
}

photoBytes = bos.toByteArray();
} // Catch clauses removed for simplicity

// Everything working OK after that (photoBytes decodes fine with the BitmapFactory)
}
}
}


And the log output:


03-01 16:32:34.139 23414-23414/my.package.my.app W/my.package.my.app:
Empty for now... 03-01 16:32:34.139 23414-23414/my.package.my.app
W/my.package.my.app: Working now !


As you can see, in the onActivityResult after taking the picture, the file is empty for the first call to FileInputStream.read... And then it can be read correctly !
I thought that when the camera intent returns to the calling activity, the file would be already written. Is there some kind of delay ? I am also surprised to see that it is always working after exactly one iteration in the for loop.

Note that if I put a breakpoint at the beginning of onActivityResult, it delays execution a bit, and everything works normally (the file is read correctly at the first try).

I am using a stock Nexus 6P under Android 6.0.1 with the stock camera app.

Any ideas ?




Important edit: As for Android N, you should use a FileProvider instead of Uri.fromFile as I did before. See this blog post and these explanations from the Android team.

Answer

File.createTempFile. Do not create that file already. The only thing you need is a file name. A file path. The Camera app will create the file. So rename your function to create new file name.