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Proper way of dismissing DialogFragment while application is in background

I started using DialogFragment, because they are working nicely through orientation changes, and stuff. But there is nasty problem I encountered.
I have AsyncTask that shows progress DialogFragment and dismisses it onPostExecute. Everything works fine, except when onPostExecute happens while application is in background (after pressing Home button, for example). Then I got this error on DialogFragment dismissing - "Can not perform this action after onSaveInstanceState". Doh. Regular dialogs works just fine. But not FragmentDialog.
So I wonder, what is the proper way of dismissing DialogFragment while application is in background? I haven't really worked with Fragments a lot, so I think that I'm just missing something.

DialogFragment has a method called dismissAllowingStateLoss()

This is what I did (df == dialogFragment):
Make sure that you call the dialog this way:
df.show(getFragmentManager(), "DialogFragment_FLAG");
When you want to dismis the dialog make this check:
if (df.isResumed()){
df.dismiss();
}
return;
Make sure that you have the following in the onResume() method of your fragment (not df)
#Override
public void onResume(){
Fragment f = getFragmentManager().findFragmentByTag("DialogFragment_FLAG");
if (f != null) {
DialogFragment df = (DialogFragment) f;
df.dismiss();
}
super.onResume();
}
This way, the dialog will be dismissed if it's visible.. if not visible the dialog is going to be dismisded next the fragment becomes visible (onResume)...

This is what I had to do to achieve what you want:
I have a Fragment activity on which i was showing a dialog fragment named fragment_RedemptionPayment which is globally declared at the top. The following code dismisses the DialogFragment if it was showing before the activity goes in background and comes back in foreground.
#Override
public void onResume() {
super.onResume();
if(fragment_RedemptionPayment.isVisible()){
fragment_RedemptionPayment.dismiss();
}
}

Another new way of checking the state before calling dismiss is this:
if(!dialog.isStateSaved){
dialog.dismiss()
} else {
//Change the UI to suit your functionality
}
In this way its is checked that state is saved or not, basically on pause and onSaveInstanceState has been called.
For Java you can use isStateSaved()

A solution that might work is setting Fragment.setRetainInstance(true) in your dialogfragment, but that's not the prettiest of fixes.
Sometimes I have noticed that I have to queue up my dialog actions to let the framework restore the state first. If you can get hold of the current Looper (Activity.getMainLooper()) and wrap that in a Handler you could try passing your dismissal to the back of the queue by posting a runnable on that queue.
I often end up using a separate fragment that it retaininstance(true) that has a ResultReceiver. So i pass on that result receiver to my jobs and handle callbacks in its onReceive (often as a router for other receivers). But that might be a bit more work than it is worth if you are using async tasks.

Android AlertDialog won't display

I have an app that shows a welcome screen via an alert dialog. I use the following code in the onCreate method of the Activity:
wsBuilder = new AlertDialog.Builder(this);
wsBuilder.setIcon(android.R.drawable.ic_dialog_alert);
wsBuilder.setTitle(R.string.instructions_title);
wsBuilder.setMessage(R.string.welcome_1);
wsBuilder.setPositiveButton(R.string.ok,
new DialogInterface.OnClickListener() {
public void onClick(DialogInterface dialog, int which) {
dialog.dismiss();
}
});
wsBuilder.show();
When I start the app, most of the time the screen darkens like it does when the dialog is going to
display, but the dialog never shows up. The screen just stays darkened and none of the touch events get through. I can click the back button on the phone to dismiss the dialog and then the app works like normal, but I can't figure out why the dialog doesn't fully display. Once in a while the dialog actually displays, but most of the time it doesn't.
Any help in running down this issue would be greatly appreciated.

OnCreate may not be the best place for it as the application is loading try using it onStart
public void onStart()
{
//Your code here
}

Activity would be better for wellcome screen.

How to save a Progress Dialog state correctly?

In my app when i do some long work i'm using a Progress Dialog while the work isn't finished.
I'm looking for it in every place but without sucess. Everything that i founded is all about saving user interface elements states.
Then, i would like to know how i can save progress dialog state correctly ?
I want this working because when the orientation screen change the app crashes.
Shoul i use onSaveInstanceState() method ? How ? I try using saving as a bundle but without succes...
Any advice would be nice...
thanks

I think, your dialog crashes on orientation change because you are not using
#Override
protected Dialog onCreateDialog(int dialogID, Bundle args)
and
showDialog(dialogID);
to show your dialog.
I had the same problem with an alert dialog. As I see it, if you don't create dialog that way, it becomes linked to your activity, and when activity is dead, the system finds that a dialog still try to access that dead activity, not new one.

You need to add this to the manifest file for the activity in which you are showing the dialog:
android:configChanges="keyboardHidden|orientation"

to handle the screen orientation you must use onRetainNonConfigurationInstance()
you can find a more extensive explanation about screen orientation here: Faster Screen Orientation.

The way I do this in my applications is overriding the onConfigurationChanged() method in the Activity like so:
#Override
public void onConfigurationChanged(Configuration config) {
//Just switch the layout without respawning the activity
super.onConfigurationChanged(config);
}
This hasn't given me any issues as of yet and my Activity doesn't reload or restart when the orientation is changed.

Dismiss dialog after screen orientation change

1) I launch a background task (via AsyncTask)
new FindJourneyTask().execute(); // FindJourneyTask extends AsyncTask
2) Still in the main thread (just before new thread is launched) I create a dialog with showDialog(dialogId)
// this method is in FindJourneyTask
protected void onPreExecute() {
showDialog(DIALOG_FINDING_JOURNEY);
}
3) Screen orientation changes and the Activity is recreated
4) How can I now dismiss the dialog from the FindJourneyTask? Calling dismissDialog(dialogId) does nothing.
// this method is in FindJourneyTask
protected void onPostExecute(FindJourneyResult result) {
dismissDialog(DIALOG_FINDING_JOURNEY); // does nothing
}

This is a common problem, and there are no real good solutions. The issue is that on screen orientation change, the entire Activity is destroyed and recreated. At the same time, the Dialog you previously had is re-created in the new Activity, but the old background task still refers to the old Activity when it tries to dismiss the dialog. The result is that it dismisses a dialog which was long ago destroyed, rather than dismissing the dialog the new orientation created.
There are three basic solutions:
Override the default orientation-handling code so that your Activity is not destroyed upon rotation. This is probably the least satisfactory answer, as it blocks a lot of code that is automatically run upon orientation changes.
Create a static member variable of your Activity that references the Activity itself, so you can call STATIC_ACTIVITY_VARIABLE.dismissDialog().
Code a solution in which the background task keeps track of the current Activity and updates itself as necessary.
These three solutions are discussed at length here: http://groups.google.com/group/android-developers/browse_thread/thread/bf046b95cf38832d/

There is a better solution to this problem now which involves using fragments.
If you create a dialog using DialogFragment, then this fragment will be responsible for maintaining your dialog's lifecycle. When you show a dialog, you supply a tag for your fragment (DialogFragment.show()). When you need to access your dialog, you just look for the necessary DialogFragment using FragmentManager.findFragmentByTag instead of having a reference to the dialog itself.
This way if device changes orientation, you will get a new fragment instead of the old one, and everything will work.
Here's some code based also in #peresisUser answer:
public void onSaveInstanceState(Bundle outState) {
AppCompatActivity activity = (AppCompatActivity) context;
FragmentManager fragmentManager = activity.getSupportFragmentManager();
DialogFragment dialogFragment = (DialogFragment) fragmentManager.findFragmentByTag("your_dialog_tag");
if(dialogFragment!=null) {
Dialog dialog = dialogFragment.getDialog();
if(dialog!=null && dialog.isShowing()) {
dialogFragment.dismiss();
}
}
}

This is long after the question was asked and answered, but i stumbled upon this problem also and wanted to share my solution...
I check in onSavedInstance() which runs on orientation change, whether the dialog is showing or not with dialog.isShowing(), and pass it into outState variable. Then in your onCreate(), you check this var if it's true. If it is, you simply dismiss your dialog with dialog.dismiss()
Hope this helps others :()

I tried adding setRetainInstance(true); on OnCreate function of DialogFragment. This will cause dialog to dismiss on rotation.

Just add this line to specific activity in your Manifest to solve this problem android:configChanges="orientation|screenSize|smallestScreenSize"
like this,
<activity
android:name=".PDFTools"
android:exported="false"
android:configChanges="orientation|screenSize|smallestScreenSize"
android:theme="#style/Theme.DocScanner.NoActionBar" />

Showing simple message dialogs

In my activity, I'd like to show simple info dialogs, stuff like:
new AlertDialog.Builder(context).setMessage(message).show();
if I do that, the dialog will leak when I rotate that phone (not to mention it will disappear as well, so the user may miss it). I can use the managed dialogs, but I'm not sure how you use it sensibly for these types of short messages? Looks like you have to do this:
showDialog(SOME_DLG_ID);
...
#Override
onCreateDialog(int id) {
if (id == SOME_DLG_ID) {
new AlertDialog.Builder(context).setMessage(message).show();
}
}
there's no way to pass what the message should be into onCreateDialog since its an override method. I'd hate to make a member variable of the parent activity that just stores whatever the current message should be. How do you all do it?
Thanks

if I do that, the dialog will leak
when I rotate that phone (not to
mention it will disappear as well, so
the user may miss it)
You can add
<activity
android:configChanges="orientation|keyboardHidden"
>
to your AndroidManifest.xml to prevent restarting the activity when the phone rotates. I am using it in my app and my AlertDialog survives the rotation of phone.

You can implement Activity.onPrepareDialog(int, Dialog) to switch out the message before the dialog is shown on the screen. So you could do something like:
#Override protected void onPrepareDialog(int id, Dialog dialog) {
if (id == SOME_DLG_ID) {
((AlertDialog) dialog).setMessage(message);
}
}
You'd still have to keep track of the message you're current showing in your activity, but at least this way, you're not creating a Dialog object for each message you want to show.

Using DialogFragment to manage the dialog ensures that it correctly handles lifecycle events such as when the user rotates the screen or presses the Back button.