Develop Reference

Show dialog on back pressed inside fragment

I've an activity and inside it a fragment.
What's the right procedure to ask for saving data (via a dialog) before exiting the activity?
User press back
Activity notify the fragment via interface onBackPressed
Fragment show dialog where user can choose to save/unsave data
User choose an option in the dialog
Fragment notify activity that calls super.onBackpressed()?
I'm not sure about point 5, because at point 2. I've to avoid default behaviour, instead at 5. I've to call super.
I need to mantain the save business logic inside the fragment.
P.S. the result is something like when FB app ask you on exit, to save or delete a post that is still a draft.

What you described works. Alternatively, for step 5, you can simply do
getActivity().finish;
if the user confirms exiting.

In the onCreateView() of the fragment, right before you return the view, add a listener to it:
v.setOnKeyListener( new OnKeyListener() {
#Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if( keyCode == KeyEvent.KEYCODE_BACK){
//do your stuff
}
return false;
}
});
return v;

Fragments, How to Navigate back to the previous Fragment, from the current Fragment?

I am using Fragment A,Fragment B .. and so on. i want to navigate back to the previous Fragment, from the current Fragment.
I want to use Back Button in Mobile to get back navigation.
How can i do this ? OR i have to make Back button in layout xml.
i tried below code,
fTransaction.add(R.id.container, nF).addToBackStack(null).commit();
when i pressed Back Button in Mobile , it restarts the App.

To go back to previous fragment using phone's back button you should override onKeyDown() mehtod.
#Override
public boolean onKeyDown(int keyCode, KeyEvent event)
{
if(keyCode == KeyEvent.KEYCODE_BACK)
{
getFragmentManager().popBackStack();
return true;
}
return false;
}

When replacing a fragment use replace instead of add and then addToBackStack:
fTransaction.replace(R.id.container, nF).addToBackStack(null).commit();

Try this:
fTransaction.addToBackStack(null).add(R.id.container, nF).commit();

Help prevent Back button from closing sub-activity

I have a main activity. It's main purpose is to handle Tab menu. If a user click a tab it'll load another activity as a sub-activity, still showing the tab menu. I am using Intent to do this:
setContent(new Intent(this,B.class))
This sub-activity has an onclick function as well. If the user clicks one of the links it'll load xml layout file using setContentView command:
setContentView(R.layout.B1);
Now, when the back button is pressed while xml file is loaded, it'll close the entire application. Is there a way to prevent this, say, return to the sub-activity or the main activity?
thanks for all your help.

You should override the onBackPressed method in your activity or sub activity:
#Override
public void onBackPressed() {
//TODO Do your task here
}

In your sub activity you should override the fallowing:
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK) //Override Keyback to do nothing in this case.
{
return true;
}
return super.onKeyDown(keyCode, event); //-->All others key will work as usual
}

Why my activities are not performing my overridden back button event?

I want to send back my activity to starting one. Let me explain you.
I am using Main activity having 4 tabs, and each tabs has his own activity. Each activity in has more activities in it.
Problem starts when I click on 1st activity in my 1st tab. The next activity is independent. I create an intent of my next activity. In such case to prevent draw my tab-bar layout in that new activity. I use my existing activity layout, remove all the view in it. Then i put new activity in it.
e.g..
contentViewLayout.removeAllViews();
View view = activityManager.startActivity(id, intent).getDecorView();
contentViewLayout.addView(view, contentViewLayoutParams);
Its done. But problem arise when device BACK button pressed. Because new activity is starting in existing activity. So when back button pressed , then it quite to main activity and application close. I want to do that in such a case "new activity" should be terminate and existing activity must start again. And then if again BACK button pressed then it should terminate main activity.
I override the onKeyDown() down method as follow but it. dose not working properly?
In my new activity.
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(keyCode == KeyEvent.KEYCODE_BACK){
childActivity = null;
contentViewLayout.removeAllViews();
mainActivity = new Intent(this,MainActivity.class);
View view = activityManager.startActivity(id, intent).getDecorView();
contentViewLayout.addView(view, contentViewLayoutParams);
return false;
}else{
return super.onKeyDown(keyCode, event);
}
}
But it always quite the application instead of closing child activity

I got it!
Actually the focused activity was the main activity... not the new activity. So all we have to do to set focused to our new activity. So in onCreate() method of new activity I put focused to one any component in new activit e.g..
button.setFocusable(true);
button.requestFocus();
So in such a case new activity onKeyDownButtonWorks
Blockquote
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if(event.getKeyCode() == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0 ){
//My code goes here.
return true;
}
return super.onKeyDown(keyCode, event);
}

Take a look at this solution:
ActivityGroup not handling back key for ListActivity

Android Back Button functionality

I'm little bit fed up with the device back button functionality.
I have two activities. From 1st I go to 2nd and display one item through array in ListView and when I presses the back button i came back to 1st activity.
when I again go to 2nd activity to display the item once again it showing me the previous items at 1st row and then the same item in the second row as well.
Means it is not removing the previous item when i presses the back button.
I have used:
public void onBackPressed ()
{
for(int i=0; i<sub_categories.length;i++)
{
sub_categories[i]="";
}
Log.d(this.getClass().getName(), "*****************back button pressed");
}

I'm not entirely sure what you are trying to do, since you are not describing where you actually delete your item.
If you really always want to delete the item you have highlighted upon leaving activity no 2, you could delete it in onStop().
If you don't want to remember the state when leaving the activity you should set android:saveEnabled="false" in your layout manifest.

You need to notify the adapter that the data has changed using notifyDataSetChanged. And the adapter will tell the ListView to update it's view.

Here is how you can run code on key press:
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if (keyCode == KeyEvent.KEYCODE_BACK && event.getRepeatCount() == 0) {
Log.d("BACK KEY PRESSED");
}
return super.onKeyDown(keyCode, event);
}
After returning to an activity, use notifyDatasetChanged in the activity onResume() to update the list.