Develop Reference

How to set back not up button on Actionbar

I have AlbumListActivity, I am fetching list of albums from internet. When album on the list is clicked, user is taken to AlbumDetailActivity. In AlbumDetailActivity when I press phone's back button, it takes me back to AlbumListActivity and when I press back button on ActionBar it again takes me back to AlbumlistActivity but reloading data in the list. I red this post and I understand that Back and Up are different things. But in this case it really does not matter because AlbumDetailActivity will not be open by another application.

on pressing the Up button, just call the
onBackPressed()
method like so:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}

Have Up button act the same as android back button

My android application has the following activity flow
Listing -> Buy -> Sell
From the listing when an item is clicked/selected an id is passed to buy to pull the relevant data from the server. If a user owns a certain item there will be a sell option as well from the buy screen (which doubles as an overview of said item).
The problem I am facing is that when you are on the sell screen and press the android back button you are taken back to the buy screen in it's original state, however when you click the back arrow (up) from the activity in the toolbar, it seems that it is actually trying to launch a new activity and throws an exception (since the activity cannot know what the id was). The buy activity is listed as a parent to the sell activity in the manifest.
I need to somehow make the up button to act the same as the back button on this particular activity, or at least pass the id back somehow.
Any suggestions would be appreciated.

If you're using an ActionBar (either platform or AppCompat) override the following method in the activity from which you wish to go back.
#Override
public boolean onOptionsItemSelected(#NonNull final MenuItem item) {
final int id = item.getItemId();
if (id == android.R.id.home) {
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}
This should be safe to use in a simple navigation hierarchy such as yours.

Just yesterday i did this for my app. This is what I did:
In manifest file I removed
<meta-data
android:name="android.support.PARENT_ACTIVITY"
android:value="com.example.app.MainActivity" />
that was part of my DetailsActivity.
In the DetailsActivity I added this line to onCreate
getSupportActionBar().setDisplayHomeAsUpEnabled(true);
and in onOptionsItemSelected() method I added these lines
if (item.getItemId() == android.R.id.home) {
onBackPressed();
}
Not sure if it is the best way to handle this but oh well it works :)

In your Activity, onOptionsItemSelected() method get the clicked item id, if the id is android.R.id.home then just finish() current activity.
Try this:
#Override
public boolean onOptionsItemSelected(MenuItem item)
{
switch(item.getItemId())
{
case android.R.id.home:
finish();
return true;
default:
return super.onOptionsItemSelected(item);
}
}

How to detect if the Up button was pressed

In my activity the action bar shows only the left arrow and the title of the activity.
When I press the left arrow the activity goes back to the previous activity, but no event is registered in the onKeyUp, OnkeyDown and OnBackPressed methods.
But when I press the Back key on the phone (at the bottom) the activity goes back to the previous one and all the methods onKeyUp, OnKeyDown and OnBackPressed register an event (in the logcat).
How can I capture that left arrow (I think it is called the UP button)?
The reason I need to capture the key is to know in the onPause method that the activity is destroyed by the user and not by the system (for example, if the user switches to another activity).
By further investigating he matter I found out that the UP button gives an event that is captured by the onOptionsItemSelected method and since there is no other button on the menu I know it is this button.

see http://developer.android.com/guide/topics/ui/actionbar.html#Handling
Handling clicks on action items
When the user presses an action, the system calls your activity's onOptionsItemSelected() method. Using the MenuItem passed to this method, you can identify the action by calling getItemId(). This returns the unique ID provided by the tag's id attribute so you can perform the appropriate action. For example:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle presses on the action bar items
switch (item.getItemId()) {
case android.R.id.home:
onUpButtonPressed();
return true;
case R.id.action_search:
openSearch();
return true;
case R.id.action_compose:
composeMessage();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
Note: If you inflate menu items from a fragment, via the Fragment
class's onCreateOptionsMenu() callback, the system calls
onOptionsItemSelected() for that fragment when the user selects one of
those items. However, the activity gets a chance to handle the event
first, so the system first calls onOptionsItemSelected() on the
activity, before calling the same callback for the fragment. To ensure
that any fragments in the activity also have a chance to handle the
callback, always pass the call to the superclass as the default
behavior instead of returning false when you do not handle the item.
To enable the app icon as an Up button, call setDisplayHomeAsUpEnabled(). For example:
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_details);
ActionBar actionBar = getSupportActionBar();
actionBar.setDisplayHomeAsUpEnabled(true);
...
}

Yes you are right, you can detect if the up button was pressed in the onOptionsItemSelected method. This should work:
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
// Do something here. This is the event fired when up button is pressed.
return true;
}
return super.onOptionsItemSelected(item);
}

Up Button in ActionBar with the possibility to move more activities

I'm doing an app for Android. In the DetailActivity, there is the ActionBar with the Up Button. When I press it, it would return in the previous activity. But the DetailActivity can be launched from different activity.

Instead of using NavUtils.navigateUpTo(this, upIntent) , you can just use finish() or onBackPressed(). This would finish the activity, and go back to the previous one. So handling of the Up button being pressed would look like this:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
// Respond to the action bar's Up/Home button
case android.R.id.home:
finish();
return true;
}
return super.onOptionsItemSelected(item);

Android Actionbar Up button versus system Back button

I'm using the Actionbar and it's "up" button to return from a detail activity to the main activity, which works fine. Similarly, the user can press the system "back" button to return to the main activity.
In my main activity, in onCreate() data is downloaded from the internet to display upon app start. I noticed that when I use the Actionbar "up" button to go from detail to main activity, onCreate() is run, re-downloading the data. But onCreate() is not run when I use the system "back" button, therefore immediately showing the main activity view.
The code I use in the detail activity to implement the "up" button is:
switch (item.getItemId()) {
case android.R.id.home:
Intent intent = new Intent(this, MainActivity.class);
intent.addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
startActivity(intent);
return true;
I would like the "up" button to behave like the "back" button and not rerun onCreate(). But I'm unsure how to make this happen, or which code path the "back" button implements to return to the main activity.
Thanks!

Instead of starting a whole new activity simply finish the details activity you are in
switch (item.getItemId()) {
case android.R.id.home:
finish();
return true;
Then you will return to the previous activity on the activity stack (your main activity) and onCreate shouldn't be called

If you want Up to do exactly what Back does, you can do this:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch(item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
default:
break;
}
return super.onOptionsItemSelected(item);
}
Note that the default implementation of onBackPressed() just calls finish(), but onBackPressed can be overridden.

I think a better solution can be found in this post.
Calling finish() works in specific situations but may not always produce the behavior described in the documentation e.g:
By calling
Intent intent = NavUtils.getParentActivityIntent(this);
intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP|Intent.FLAG_ACTIVITY_SINGLE_TOP);
NavUtils.navigateUpTo(this, intent);
you'll return to the parent activity in the state in which you left it. If you have a flat app structure, it'll still act just like the Back button.

for a real "home" functionality , you should see the api demos ,under "App/Activity/Reorder Activities" .
the reason : what if you have something like this : activity1->activity2->activity3 , and now you wish to go to activity1 by pressing the home button on the action bar?

I believe the simplest way is to override the "getParentActivityIntent" method of the detail activity adding the flag "Intent.FLAG_ACTIVITY_CLEAR_TOP":
#Nullable
#Override
public Intent getParentActivityIntent() {
Intent intent = super.getParentActivityIntent();
if (intent != null) {
return super.getParentActivityIntent().addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
}
return intent;
}

There is another solution which can be in hand for somebody. I had the same double-behavior when user pressed Back and ActionbarBack buttons. I was fine with Back btn behaviour. I didn't want an activity to be recreated. So I overrode the method
#Override
public boolean onSupportNavigateUp() {
onBackPressed();
return true;
}
Works fine for me