Develop Reference

Android make an activity pause running when it is not in the front of the stack

I have an activity which holds a fragment called paymentfragment, paymenfragment holds all the cards a person has. Then I have an activity called addcardactivity which is where a user can add cards. There is a button on the paymentfragment which takes the user to the addcardactivity, but when they are done adding their new card I want the user to go back to the paymentfragment and I want the payment fragment to refresh so that it can hold the new card.
The way I am doing, it is not to end the paymentfragment, and once the addcardactivity is done i finish that activity, the only problem is then it does not refresh.
This is the relevant code from the paymentfragment
#Override
public void onClick(View v) {
Intent intent = new Intent(getActivity(), AddCardActivity.class);
getActivity().startActivity(intent);
}
Now ideally, under the startactivity, i would run the method refreshtasks();
however that doesn't work because it just runs it too early.
Any ideas?

Send data to activity which is running in background

Having trouble passing data between activities.
ListActivity is collecting data and when back button is pressed returns to MainActivity and then want to get that data via onResume method but I don't get anything.
How can this problem be solved?
ListActivity.java
#Override
public void finish() {
i = new Intent(ArrayListActivity.this, MainActivity.class);
i.putParcelableArrayListExtra(Constants.TAG_SELECTED_PRODUCT_LIST, selected_list);
super.finish();
}
MainActivity.java
#Override
protected void onResume() {
super.onResume();
Bundle extras = getIntent().getExtras().getBundle(Constants.TAG_SELECTED_PRODUCT_LIST);
if(extras != null) {
selected_list = extras.getParcelableArrayList(Constants.TAG_SELECTED_PRODUCT_LIST);
myListView.setAdapter(new ProductAdapter(MainActivity.this,
R.layout.array_lisviewt_item_row, selected_list));
}
}

You probably want to start your second activity from the first one via the startActivityForResult(...) method.
This method allows you to transport results from a launched activity back to it's launching activity.
From the documentation:
Launch an activity for which you would like a result when it finished.
When this activity exits, your onActivityResult() method will be
called with the given requestCode. Using a negative requestCode is the
same as calling startActivity(Intent) (the activity is not launched as
a sub-activity).

You'll want to start the activity with startActivityForResult() and override onActivityResult() to handle the data you return from the second Activity.
Check out this article on the Android developers site for more info.

Perhaps you should
Call your ListActivity with startActivityForResult(), from your MainActivity.
Once you finished working on the ListActivity, you call setResult() to set the data, followed by finish().
This will bring you back to your previous MainActivity. So how do you retrieve the data set by your ListActivity?
In MainActivity, override onActivityResult().
There's a brief explanation of this mechanism in Starting Activities and Getting Results.

onResume() not called second time an Activity is launched

During the normal course of development, I noticed that a particular activity appears to have stopped responding the second time it is called.
i.e. menu->(intent)->activity->(back button)->menu->(intent)
There is nothing relevant in logcat.
I don't even know where to start debugging this nor what code to show so here are the onClick and onResume fragments:
if (!dictionary.getClassName().equals("")) {
this.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
Intent i;
i = new Intent(mContext, NVGlobeNavigatorVC.class);
i.putExtra("PAGE_TITLE", title);
i.putExtra("TITLE", _dictionary._title);
mContext.startActivity(i);
});
} else {
findViewById(R.id.greaterthan).setVisibility(View.GONE);
}
and in the Activity being launched:
#Override
protected void onResume() {
super.onResume();
...
Nothing unusual in manifest either:
<activity
android:name=".NVViews.NVGlobeNavigatorVC"
android:theme="#style/WindowTitleBackground"
android:label="GlobeNavigator"/>
For clarity, I put breakpoints on mContext.startActivity(i) and super.onResume(). I click the view with the onClickListener and both breakpoints are hit as expected. I then press the back button which returns me to the menu. onPause() is called as expected.
I touch the view to launch the activity again, and the breakpoint on startActivity is hit but not in onResume() in the target activity. The screen goes black and the only way I can get going again is to restart the app. If I pause the debugger, it pauses in dalvik.system.NativeStart() which implies that the activity is never relaunched.
I don't think it's relevant, but I'm using Intellij IDEA and have deleted all of the output directories, invalidated the caches and done a full rebuild.
Target API is 8. I've tested on 2.3 and 4.0.4.
Any ideas? I'm stumped.
[EDIT]
In onPause, I save some stuff to prefs. The purpose of onResume() is to get them back again:
#Override
protected void onPause() {
super.onPause();
SCPrefs.setGlobeViewViewPoint(globeView.getViewPoint());
SCPrefs.setGlobeViewZoom(globeView.getZoom());
SCPrefs.setGlobeViewScale(globeView.getScale());
}

This code:
i = new Intent(mContext, NVGlobeNavigatorVC.class);
creates a new intent. The intent is of class NVGlobeNavigatorVC.class.
If you call it once, you create a new activity, lets call it "iTheFirst". If you back out of the activity, it executes "on pause". When you run the above code again, you create another new activity of the same class, but a different acitivity. Hence it won't resume your other activity, but make a new one that we could call "iTheSecond". It looks just like iTheFirst but is unique.
If you want to resume the above, after backing out of it, you need to keep a reference to it in your menu. Then in your onClick, look to see if that activity exists, and if not, make a new one and start it, and if it does exist, just resume it.
Here is a sample activity that remembers and restarts an activity:
Intent savedCueCardActivity = null;
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState, R.layout.landing);
}
public void goToNextScreen(View v) {
if (savedCueCardActivity == null) {
savedCueCardActivity = new Intent().setClass(this, CueCardActivity.class);
startActivity(savedCueCardActivity);
// lastActivity.finish();
} else {
savedCueCardActivity.setFlags(Intent.FLAG_ACTIVITY_REORDER_TO_FRONT);
startActivity(savedCueCardActivity);
}
overridePendingTransition(R.anim.fade_in, R.anim.fade_out);
}

I found the problem, and it's a bit esoteric.
I have a large static data structure which is loaded in a class static initialiser. There was a bug in that initialiser causing an infinite loop the second time it was called if the data structure was still loaded.
Because that class is referenced in my Activity, the class loader is loading it before onCreate() or onResume() is called.
The loop gave the appearance that the Activity loader had hung.

Destroy Activity stack

There are some applications in which you can logout at any point within. e.g you login and then your browse around. you use the action bar or the menu button to logout. I can call finish() at that very point but then it will just pop the last activity. Even if i move the user forward to the Home Activity, still the stack remains in memory. Is there any way to destroy the remaining stack?

The easiest way to do this is to clear the stack back to your home or first activity, and pass an identifier saying to exit the app. For example:
public class ActivityOne extends Activity {
public static final String FINISH_THIS = "FINISH_THIS";
#Override
protected void onNewIntent(Intent intent) {
super.onNewIntent(intent);
if(intent.hasExtra(FINISH_THIS)) {
finish();
}
}
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if(getIntent().hasExtra(FINISH_THIS)) {
finish();
}
}
}
public class ActivityTwo extends Activity {
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if(item.getItemId() == R.id.logout) {
Intent intent = new Intent(this, ActivityOne.class);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
intent.putExtra(ActivityOne.FINISH_THIS, true);
startActivity(intent);
}
return true;
}
}
If ActivityOne is the root of your stack and ActivityTwo is where the user selected the option to logout, starting an intent that clears back to ActivityOne will get rid of the backstack. If you want the app to exit when logging out, you can pass an extra like I did with FINISH_THIS to signal the root/home activity to finish.
Another way to do this would be to call setResult(FINISH_THIS) where FINISH_THIS is an int identifier before calling finish(). Then in all other activities in the stack, you'd override onActivityResult and check the result to see if that activity needs to be finished. If it does, you set the result again and keep passing it down the line.
Using the intent method I outlined in the beginning is the preferred method for clearing the stack as it doesn't rely on daisy chaining results together but both options work well enough.

A quick and dirty way to do it would be onResume verify you are still logged in, if not then finish it. That way if they hit back, it will close each activity as it tries to open them. This would also prevent someone from using the app manager to re-enter your activity when you expect it to be closed.
Another idea would be read Android: Clear the back stack

Activity group does not refresh activities when back button is clicked

I have a tabhost on my application and I'm using an Activity group which handles 3 activities inside.
Example:
ActivityGroup Handles
A -> B -> C
When i start this activities i'm using the flag Intent.FLAG_ACTIVITY_CLEAR_TOP.
My problem is when the user goes from A->B->C and press back button, my B activity shows up, but it does not resume or reload or refresh. It has the same state as before.
For example if the user goes again to C, C is refreshed, but when from C goes back.... B is not.
On B I have implementend methods such as onResume, onStart, onReestart and debugging it the main thread never goes in there...
And i need to refresh B because C can make changes that change the content displayed on B.
I have googleled this for 3 days and I couldn't found a solution..

I had this problem too.
I was using ActivityGroup code based on this blog post.
When I pressed the back button the pervious View would load fine, but the activity associated with it would not fire the onResume().
I was using an extended activity with on overridden and public onResume().
I found this blog post, so tried casting the view as my extended activity and called onResume().
Bingo.
Edit.... here's some more detail...
public class YFIMenuListActivity extends ListActivity {
....
#Override
public void onResume() {
super.onResume();
}
....
}
onResume() is normally protected, but I override it and make it public so that my ActivityGroup can call it.
I only have extended list activities in this activity group (I was just playing around). If you have different activities, each will have to override onResume() and I guess you'd have to look at the type of context you got back from v.getContext() before casting and calling it.
My ActivityGroup looks something like this:
public class BrowseGroup extends ActivityGroup {
.....
#Override
protected void onResume() {
super.onResume();
// call current activity's onResume()
View v = history.get(history.size()-1);
YFIMenuListActivity currentActivity = (YFIMenuListActivity)v.getContext();
currentActivity.onResume();
}
....
}

I've managed to implement an expanded version of cousin_itt's approach.
In both of my activities being used within the activity group I changed onResume from :
protected void onResume()
to
public void onResume()
I then wrote the following onResume function in my ActivityGroup to manually fire off onResumes:
#Override
protected void onResume() {
super.onResume();
View v = history.get(history.size()-1);
MainPeopleView currentActivity = null;
try {
currentActivity = (MainPeopleView)v.getContext();
currentActivity.onResume();
}
catch ( ClassCastException e ) {
Log.e(TAG, e.toString());
}
ProfileView otherActivity = null;
try {
otherActivity = (ProfileView)v.getContext();
otherActivity.onResume();
}
catch ( ClassCastException e ) {
Log.e(TAG, e.toString());
}
}
I have to say, this feels like the worst android hack I've ever written. I'm never using activitygroup again.

((ReportActivity)getLocalActivityManager().getActivity("ReportActivity")).onResume();
ReportActivity is that name you want to back Activity
ps: v.getContext();
only return the ActivityGroup ,it can't invoke child Activity onResume

I have found that onFocusChanged(boolean hasFocus) is great for situations like ActivityGroup. This will fire, even if onResume() does not. I use it for a few of my apps that have TabHosts and ActivityGroups. Here you can force the refresh and insure that it always gets fired when your Activity regains the focus.

I hope you have write your refresh data code in this method onResume().