次のコードAsyncTaskを使用してをスケジュールしましたTimer
public void toCallAsynchronous() {
TimerTask doAsynchronousTask;
final Handler handler = new Handler();
Timer timer = new Timer();
doAsynchronousTask = new TimerTask() {
@Override
public void run() {
// TODO Auto-generated method stub
handler.post(new Runnable() {
public void run() {
try {
if(mLoggedIn)
{
DownloadRandomPicture download = new DownloadRandomPicture(this, mApi, CLIENT_ID, mImage);
download.execute();
}
} catch (Exception e) {
// TODO Auto-generated catch block
}
}
});
}
};
timer.schedule(doAsynchronousTask, 0,50000);//execute in every 50000 ms
}
@Override
protected Boolean doInBackground(Void... params) {
try {
if (mCanceled) {
return false;
}
// Get the metadata for a directory
Entry dirent = mApi.metadata(mPath, 1000, null, true, null);
if (!dirent.isDir || dirent.contents == null) {
// It's not a directory, or there's nothing in it
mErrorMsg = "File or empty directory";
return false;
}
// Make a list of everything in it that we can get a thumbnail for
ArrayList<Entry> thumbs = new ArrayList<Entry>();
for (Entry ent: dirent.contents) {
if (ent.thumbExists) {
// Add it to the list of thumbs we can choose from
thumbs.add(ent);
}
}
if (mCanceled) {
return false;
}
if (thumbs.size() == 0) {
// No thumbs in that directory
mErrorMsg = "No pictures in that directory";
return false;
}
// Now pick a random one
int index = (int)(Math.random() * thumbs.size());
Entry ent = thumbs.get(index);
String path = ent.path;
mFileLen = ent.bytes;
String cachePath = mContext.getCacheDir().getAbsolutePath() + "/" + IMAGE_FILE_NAME;
try {
mFos = new FileOutputStream(cachePath);
} catch (FileNotFoundException e) {
mErrorMsg = "Couldn't create a local file to store the image";
return false;
}
// This downloads a smaller, thumbnail version of the file. The
// API to download the actual file is roughly the same.
mApi.getThumbnail(path, mFos, ThumbSize.BESTFIT_960x640,
ThumbFormat.JPEG, null);
if (mCanceled) {
return false;
}
mDrawable = Drawable.createFromPath(cachePath);
// We must have a legitimate picture
return true;
} catch (DropboxUnlinkedException e) {
// The AuthSession wasn't properly authenticated or user unlinked.
} catch (DropboxPartialFileException e) {
// We canceled the operation
mErrorMsg = "Download canceled";
} catch (DropboxServerException e) {
// Server-side exception. These are examples of what could happen,
// but we don't do anything special with them here.
if (e.error == DropboxServerException._304_NOT_MODIFIED) {
// won't happen since we don't pass in revision with metadata
} else if (e.error == DropboxServerException._401_UNAUTHORIZED) {
// Unauthorized, so we should unlink them. You may want to
// automatically log the user out in this case.
} else if (e.error == DropboxServerException._403_FORBIDDEN) {
// Not allowed to access this
} else if (e.error == DropboxServerException._404_NOT_FOUND) {
// path not found (or if it was the thumbnail, can't be
// thumbnailed)
} else if (e.error == DropboxServerException._406_NOT_ACCEPTABLE) {
// too many entries to return
} else if (e.error == DropboxServerException._415_UNSUPPORTED_MEDIA) {
// can't be thumbnailed
} else if (e.error == DropboxServerException._507_INSUFFICIENT_STORAGE) {
// user is over quota
} else {
// Something else
}
// This gets the Dropbox error, translated into the user's language
mErrorMsg = e.body.userError;
if (mErrorMsg == null) {
mErrorMsg = e.body.error;
}
} catch (DropboxIOException e) {
// Happens all the time, probably want to retry automatically.
mErrorMsg = "Network error. Try again.";
} catch (DropboxParseException e) {
// Probably due to Dropbox server restarting, should retry
mErrorMsg = "Dropbox error. Try again.";
} catch (DropboxException e) {
// Unknown error
mErrorMsg = "Unknown error. Try again.";
}
return false;
}
protected void onProgressUpdate(Long... progress) {
int percent = (int)(100.0*(double)progress[0]/mFileLen + 0.5);
//mDialog.setProgress(percent);
}
@Override
protected void onPostExecute(Boolean result) {
//mDialog.dismiss();
if (result) {
// Set the image now that we have it
mView.setImageDrawable(mDrawable);
} else {
// Couldn't download it, so show an error
showToast(mErrorMsg);
}
}
私はこれonCreateを私の活動から呼んでいます。私の非同期タスクは基本的にサーバーからいくつかのデータをダウンロードします。メインアクティビティでは、ユーザーがサーバーにログインしてから、データの取得に進みます。私が直面している問題は、各AsyncTaskが独自のスレッドを作成することです。また、これらはいずれも完了しません。スレッドのステータスは常に実行中です。新しいAsyncTaskが以前のAsyncTaskが終了したときにのみ起動されることを確認する方法はありますか？