我正在开发一款智能手机/平板电脑应用程序，使用一个APK，在需要时根据屏幕大小加载资源，最佳设计选择似乎是通过ACL使用Fragment。
这个应用程序一直运行良好，只基于活动。以下是我在活动中处理AsyncTasks和ProgressDialogs的模拟类，以便在通信过程中屏幕旋转或配置更改时仍能工作。
我不会更改清单以避免重新创建活动，有很多原因我不想这样做，但主要是因为官方文档说这不被推荐，并且我到目前为止已经成功地管理了它，所以请不要推荐这种方法。
public class Login extends Activity {
static ProgressDialog pd;
AsyncTask<String, Void, Boolean> asyncLoginThread;
@Override
public void onCreate(Bundle icicle) {
super.onCreate(icicle);
setContentView(R.layout.login);
//SETUP UI OBJECTS
restoreAsyncTask();
}
@Override
public Object onRetainNonConfigurationInstance() {
if (pd != null) pd.dismiss();
if (asyncLoginThread != null) return (asyncLoginThread);
return super.onRetainNonConfigurationInstance();
}
private void restoreAsyncTask();() {
pd = new ProgressDialog(Login.this);
if (getLastNonConfigurationInstance() != null) {
asyncLoginThread = (AsyncTask<String, Void, Boolean>) getLastNonConfigurationInstance();
if (asyncLoginThread != null) {
if (!(asyncLoginThread.getStatus()
.equals(AsyncTask.Status.FINISHED))) {
showProgressDialog();
}
}
}
}
public class LoginThread extends AsyncTask<String, Void, Boolean> {
@Override
protected Boolean doInBackground(String... args) {
try {
//Connect to WS, recieve a JSON/XML Response
//Place it somewhere I can use it.
} catch (Exception e) {
return true;
}
return true;
}
protected void onPostExecute(Boolean result) {
if (result) {
pd.dismiss();
//Handle the response. Either deny entry or launch new Login Succesful Activity
}
}
}
}
这段代码很好用，在大约1万个用户中没有出现任何问题，所以直接将此逻辑复制到新的基于碎片的设计中似乎是合理的，但是，当然，它不起作用了。
这是LoginFragment:
public class LoginFragment extends Fragment {
FragmentActivity parentActivity;
static ProgressDialog pd;
AsyncTask<String, Void, Boolean> asyncLoginThread;
public interface OnLoginSuccessfulListener {
public void onLoginSuccessful(GlobalContainer globalContainer);
}
public void onSaveInstanceState(Bundle outState){
super.onSaveInstanceState(outState);
//Save some stuff for the UI State
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//setRetainInstance(true);
//If I setRetainInstance(true), savedInstanceState is always null. Besides that, when loading UI State, a NPE is thrown when looking for UI Objects.
parentActivity = getActivity();
}
@Override
public void onAttach(Activity activity) {
super.onAttach(activity);
try {
loginSuccessfulListener = (OnLoginSuccessfulListener) activity;
} catch (ClassCastException e) {
throw new ClassCastException(activity.toString() + " must implement OnLoginSuccessfulListener");
}
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
RelativeLayout loginLayout = (RelativeLayout) inflater.inflate(R.layout.login, container, false);
return loginLayout;
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
//SETUP UI OBJECTS
if(savedInstanceState != null){
//Reload UI state. Im doing this properly, keeping the content of the UI objects, not the object it self to avoid memory leaks.
}
}
public class LoginThread extends AsyncTask<String, Void, Boolean> {
@Override
protected Boolean doInBackground(String... args) {
try {
//Connect to WS, recieve a JSON/XML Response
//Place it somewhere I can use it.
} catch (Exception e) {
return true;
}
return true;
}
protected void onPostExecute(Boolean result) {
if (result) {
pd.dismiss();
//Handle the response. Either deny entry or launch new Login Succesful Activity
}
}
}
}
}
由于必须从Activity而不是Fragment中调用onRetainNonConfigurationInstance()和getLastNonConfigurationInstance()，因此我无法使用它们。我已经阅读了一些类似的问题，但没有答案。
我理解在片段中正确组织这些内容可能需要一些解决方法，但是，我希望保持相同的基本设计逻辑。
在配置更改期间保留AsyncTask的正确方法是什么？如果它仍在运行，则显示进度对话框，考虑到AsyncTask是片段的内部类，而且是片段本身调用AsyncTask.execute()的呢？
Fragment处理配置更改 - Alex Lockwood