Develop Reference

Purpose of Android Back button, is it OK or Cancel?

I'm new to Android development, even to the androidOS, this is a more of a experience question on how do I approach on a OK or Cancel for a list of choices, Let's say a list of languages with a name and a checkbox next to it.
There's a back arrow button at the bottom of screen for each app, does that mean Cancel or that means I'm OK with the selection? I also noticed a toolbar back button, does that mean OK or Cancel? (attached screenshot).
What's the expectation of user for each of these back buttons so I can program my app accordingly?

I see hitting back as neither OK nor Cancel but a mechanism to navigate back to a previous Activity or Fragment. I usually refer to the back button to the left of the toolbar as the "in-app" back button, where as the system back button as the "system" back button, or "hardware" back button depending on the device.

You can also change the default behavier of the toolbar back arrow button with this code
public boolean onOptionsItemSelected(#NonNull MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
try {
int id = item.getItemId();
switch (id) {
case android.R.id.home: {
//anything you want here
return true;
}
case R.id.settings: {
Intent intent = new Intent(this, Settings.class);
startActivity(intent);
return true;
}
}
} catch (Exception e) {
e.printStackTrace();
}
return super.onOptionsItemSelected(item);
}

It normally means cancel, you can change that with this piece of code:
#Override
public void onBackPressed{
//anything you want here
}

Back Arrow press exiting the App in Android [duplicate]

I want to customize the activity back button in action bar, not in hard key back button. I have overriden the onBackPressed() method. It works with my emulator back button, but not with action bar back button.
I want it to happen with action bar. How can I do this?
Here is my code:
#Override
public void onBackPressed() {
Toast.makeText(getApplicationContext(),"Back button clicked", Toast.LENGTH_SHORT).show();
return;
}
I have used this toast whether back pressed is working or not but the actual implementation changes like to move back to previous activity. But this is not working with the button present on top of action bar (besides title of the activity).
Please any one could specify me the problem.

I think you want to override the click operation of home button. You can override this functionality like this in your activity.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
Toast.makeText(getApplicationContext(),"Back button clicked", Toast.LENGTH_SHORT).show();
break;
}
return true;
}

If you want ActionBar back button behave same way as hardware back button:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
onBackPressed();
return true;
}
return false;
}

Two things to keep in mind that the user can either press back button or press the actionbar home button.
So, if you want to redirect him to the same destination then you can do this.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
}
return false;
}
#Override
public void onBackPressed() {
super.onBackPressed();
Intent intent = new Intent(CurrentActivity.this, NextActivity.class);
startActivity(intent);
finish();
}
This will take the user to the intent pressing either key or the action bar button.

Sorry mine is a late answer, but for anyone else arriving at this page with the same question, I had tried the above:
#Override
public boolean onOptionsItemSelected(MenuItem item) {
...
if (item.getItemId() == android.R.id.home) {
....
}
....
}
but this failed to catch the "Back" button press.
Eventually I found a method that worked for me on https://stackoverflow.com/a/37185334/3697478 which is to override the "onSupportNavigateUp()" as I am using the actionbar from the "AppCompatActivity" support library. (There is an equivalent "onNavigateUp()" for the newer actionbar/toolbar library.)
#Override
public boolean onSupportNavigateUp(){
finish();
return true;
}
and I removed the "android:parentActivityName=".MainActivity" section from the manifest file.

#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
finish();
break;
}
return true;
}

(1) Add Parent activity for your child activity (AndroidManifest.xml)
<activity
android:name=".ParentActivity" />
(2) override the onSupportNavigateUp method inside the child activity
#Override
public boolean onSupportNavigateUp() {
onBackPressed();
return false;
}

I have achieved this, by using simply two steps,
Step 1: Go to AndroidManifest.xml and in the add the parameter in tag - android:parentActivityName=".home.HomeActivity"
example :
<activity
android:name=".home.ActivityDetail"
android:parentActivityName=".home.HomeActivity"
android:screenOrientation="portrait" />
Step 2: in ActivityDetail add your action for previous page/activity
example :
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
return true;
}
return super.onOptionsItemSelected(item);
}

If you want to return to the previous instance of an Activity by pressing of ActionBar home button, without recreating it, you can override getParentActivityIntent method to use the one from the back stack:
#TargetApi(Build.VERSION_CODES.JELLY_BEAN)
#Override
public Intent getParentActivityIntent() {
return super.getParentActivityIntent().addFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP);
}
EDIT:
Also you can achieve the same result by
setting the launchMode of your parent activity to singleTop.
So setandroid:launchMode="singleTop" to parent activity in your manifest.
Or you can use flag FLAG_ACTIVITY_CLEAR_TOP with the UP intent.
reference: Providing Up Navigation

#Override
public boolean onOptionsItemSelected(MenuItem item) {
// Handle action bar item clicks here. The action bar will
// automatically handle clicks on the Home/Up button, so long
// as you specify a parent activity in AndroidManifest.xml.
int id = item.getItemId();
if (id == android.R.id.home) {
onBackPressed();
return true;
}
//noinspection SimplifiableIfStatement
if (id == R.id.signIn) {
return true;
}
return super.onOptionsItemSelected(item);
}
///////////////////
#Override
public void onBackPressed() {
super.onBackPressed();
finish();
}

There are several ways how to set up back button in bar:
1) method .setDisplayHomeAsUpEnabled(true); will do it, and then you can simply override android.R.id.home
2) adding <meta-data android:name="android.support.PARENT_ACTIVITY" android:value="my.package.parrent" /> in Android Manifest, but in this case you can not override android.R.id.home in OnOptionsMenuSelected.
.. for those who wonder why it doesn't work for them...

simulate up when back button is pressed

I'm working on an android app and recently, I discovered that the default back button onBackPressed() produces a back behaviour, while the getSupportActionBar().setDisplayHomeAsUpEnabled(true) produces an up behaviour. And the two have significant differences.
I was wondering if I can simulate the up behaviour when I press the hardware back button, so that it navigates up instead of back.
Thanks.

You can do this.
#Override
public void onBackPressed() {
NavUtils.navigateUpFromSameTask(this);
}

You can do this
Overide onOptionsItems Selected
Create a switch case of android.R.id.home
Call method onBackPressed();
here is the code
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onBackPressed();
default:
return super.onOptionsItemSelected(item);
}
}

Shared element transition when using ActionBar Back button

I am working on animating an element between two activities using code like this:
Pair<View, String> pair1 = Pair.create(sharedView, transitionName);
Pair<View, String> pair2 = Pair.create(sharedBackgroundView, transitionBackgroundName);
ActivityOptionsCompat transitionActivityOptions = ActivityOptionsCompat.makeSceneTransitionAnimation(MainActivity.this, pair1, pair2);
startActivity(myIntent, transitionActivityOptions.toBundle());
This works great when I`m using phone's back button to get back tot the initial activity, but when I use back button from the Action Bar the transition animation is no longer present. I there any work around for it?
The problem can be seen in the following clip, first time I use phone on screen back button and second time I use Back button form the Action Bar.
https://www.youtube.com/watch?v=Wtdcw2fGBTg

Here is better solution I'm using.
#Override
public boolean onOptionsItemSelected(MenuItem item) {
if (item.getItemId() == android.R.id.home) {
finishAfterTransition();
return true;
}
return false;
}
Note: finishAfterTransition() call requires Minimum API Level 21.

Intercept the click on home button and call the super onBackPressed()
#Override
public boolean onOptionsItemSelected(android.view.MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
onClickHome();
return true;
default:
return super.onOptionsItemSelected(item);
}
}
protected void onClickHome() {
super.onBackPressed();
}

Make app icon clickable without back icon

Can i make my Action Bar app icon clickable without displaying the back icon?
This is my code, it works, I have only layout problem:
actionBar.setDisplayHomeAsUpEnabled(true);
#Override
public boolean onOptionsItemSelected(MenuItem item) {
switch (item.getItemId()) {
case android.R.id.home:
//Do stuff
return true;
default:
return super.onOptionsItemSelected(item);
}
}
This is my activity layout, what I want is remove back icon, is it possible?

Try to use setHomeButtonEnabled(boolean enabled) instead of setDisplayHomeAsUpEnabled(boolean enabled). The latter do exactly the same thing as former which is enabling home button but additionally put up affordance sign which you want to get rid off.