AsyncTask 2014-12-04 Android

/ @hydrakecat

AsyncTask ...

Android Thread Looper

Processes and Threads | Android DevelopersHandling Runtime Changes | Android DevelopersEfficient Android Threading (Anders Goransson)

Android View UI UI 5 ANR (Application Not Responding)

Android Basic ThreadHandlerThreadExecutorAsyncTaskServicesAsyncQueryHandlerLoader

Android Basic ThreadHandlerThreadExecutorAsyncTaskServicesAsyncQueryHandlerLoader

AsyncTask http://developer.android.com/reference/android/os/AsyncTask.html UI Thread Handler Executor AsyncTask

AsyncTask 1@Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); ... new AsyncTask(){ @Override protected void onPreExecute() { super.onPreExecute(); mProgressDialog.show(); } @Override protected String doInBackground(Void... value) { try { Thread.sleep(15000); } catch (InterruptedException e) { } return "AsyncTask Done"; } @Override protected void onPostExecute(String result) { mProgressDialog.dismiss(); mTextView.setText(result); } }.execute();

IllegalArgumentException Configuration Chage Activity Fragment detach mProgressDialog.dismiss() IllegalArgumentException ConfigurationChange

IllegalArgumentException

onDestroy null @Override public void onCreate(Bundle savedInstanceState) { ... new AsyncTask(){ ... @Override protected void onPostExecute(String result) { if (mProgressDialog != null) { mProgressDialog.dismiss(); } if (mTextView != null) { mTextView.setText(result); } } }.execute(); } @Override public void onDestroy() { if (mProgressDialog != null && mProgressDialog.isShowing()) { mProgressDialog.dismiss(); } mProgressDialog = null; }

ProgressDialog !

Configuration change Activity AsyncTask Thread AsyncTaskLoader Activity

AsyncTask 2Fragment#getActivity() null Configuration Chage Fragment detach

@Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { ... new AsyncTask(){ ... @Override protected void onPostExecute(String[] result) { mAdapter = new ArrayAdapter(getActivity(), R.layout.listrow, result); mListView.setAdapter(mAdapter); } }.execute(); }

NullPointerException Fragment#isAdded() mAdapter @Override public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) { ... new AsyncTask(){ ... @Override protected void onPostExecute(String[] result) { if (isAdded() && mAdapter != null) { mAdapter.addAll(Arrays.asList(result)); mAdapter.notifyDatasetChanged(); } } }.execute(); }

AsyncTask 3

task = new AsyncTask(){ ...}.execute();

non-static ActivityAsyncTask GC

: Efficient Android Threading

non-static static Activity#onDestory() Activity AsyncTask#cancel() Activity Weak Reference@Override public void onCreate(Bundle savedInstanceState) { ... mTask = new MyTask(this); mTask.execute();}

@Override protected void onDestroy () { super.onDestroy(); mTask.setActivity(null); mTask.cancel(true);}

private static class MyTask extends AsyncTask { ...}

AsyncTask#cancel(false)isCanceledtrueAsyncTask#cancel(true)private static class MyTask extends AsyncTask { @Override protected String doInBackground(Void... params) { for (int i=0; i

AsyncTask 4AsyncTask sequentialconcurrentAPI Service AsyncTask Activity AsyncTask

API targetSdkVersion execute executeOnExecutor1-3 Any Sequential Not available4-10 Any Concurrent Not available11-12 Any Concurrent Sequential/Concurrent (customizable)13+

API

2.3AsyncTasktargetSdkVersion < 13 API

if (Build.VERSION.SDK_INT

AsyncTask

non-static inner class Activity#onDestroy() Activity AsyncTaskLoader Executor HandlerThread