Develop Reference

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();

show navigation drawer on physical menu button

I want to show the navigation drawer when the user clicks on the physical menu button, I override the menu button like the following :
#Override
public boolean onKeyDown(int keyCode, KeyEvent event) {
if ( keyCode == KeyEvent.KEYCODE_MENU ) {
// some code here to show navigation drawer
return true;
}
return super.onKeyDown(keyCode, event);
}
But I don't know what should I do to show the navigation drawer inside this method.

DrawerLayout.openDrawer(Gravity.LEFT) is what you are looking for. Btw I don't think that it is a bad think to do, since a lot of people is not familiar with the drawer yet.

Well, somewhere in your layout you have a DrawerLayout, which consists of your main view and your navigation drawer view.
Now you can do ...
final DrawerLayout drawerLayout = (DrawerLayout)findViewById(R.id.drawer_layout);
final View navigation = ((NavigationDrawer)drawerLayout.findViewById(R.id.navigation_drawer));
if(drawerLayout.isDrawerOpen(navigation)) drawerLayout.closeDrawer(navigation);
else drawerLayout.openDrawer(navigation);

Making back button and action bar back the same

For example, I have 2 activities which are named Main and Photos. I start Photos from Main. When I press back button when Photos activity opened, my navigation drawer menu is still selected. However, if I press back menu on action bar, Main activity refreshes, so selection disappears. I want to apply action bar back's event on back button. How can I do?

Its better to make your action bar button implement androids back buttons action rather than vice-versa, however, it can be done.
// Newer, but Im not sure what API version it came in
#Override
public void onBackPressed() {
//super.onBackPressed();
mMyAbBackBtn.callOnClick();
}
// Older, still supported
#Override
public boolean onKeyUp(int keyCode, KeyEvent event) {
if (KeyEvent.KEYCODE_BACK == keyCode) {
mMyAbBackBtn.callOnClick();
return true; //handled
}
return super.onKeyUp(keyCode, event);
}

The "back button on action bar" is actually called an Up button. Just to clarify the differences: the Back button returns you to the previous activity (this could bring you to a different app) while the Up button will return you to the previous activity in the current application.
I'm quite confused how you have an Up button and a navigation drawer at the same time, would you put up some screenshots?
Assuming your "navigation drawer menu" isn't a native part of android that you're talking about, I don't recommend overriding your Back button to get your desired behavior.
Instead consider overriding onActivityCreated or onResume:
#Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(); // don't restore the state
// alternatively:
// super.onActivityCreated(savedInstanceState); // you may have other things you
// want to preserve
// unSelect(); // your code to unselect whatever your navigation menu drawer is
}
#Override
public void onResume()
{
super.onResume();
unSelect(); // your code to unselect whatever your navigation menu drawer is
}

Android: onBackPressed() not being called when navigation drawer open

I have a main activity that is situated with two navigation drawers. The left one is always accessible, but the right one is used for displaying some necessary lists and performing certain actions. When I have certain fragments loaded into the center FrameLayout of the activity they have actions that require the right drawer be opened and an item be selected. All of this is working great, but I want to make sure that when either the back button is pressed or the screen is clicked outside the drawer that the drawer is closed, locked and the fragment loaded in there is removed. I should also mention that this right drawer holds a FrameLayout and relies on fragments.
In my main activity this is what I'm calling:
#Override
public void onBackPressed(){
Log.d(TAG, "onBackPressed() called");
if(drawerLayoutRight.isDrawerOpen(drawerFrameRight)){
Log.d(TAG, "----------------------");
drawerLayoutRight.closeDrawer(drawerFrameRight);
drawerLayoutRight.setDrawerLockMode(1, drawerFrameRight);
ExcerciseList fragment = (ExcerciseList) getFragmentManager().findFragmentById(R.id.right_drawer);
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.remove(fragment).commit();
} else {
super.onBackPressed();
}
}
I also tried:
public boolean onKeyDown(int keyCode, KeyEvent event){
if (keyCode == KeyEvent.KEYCODE_BACK) {
Log.d(TAG, "onKeyDown called");
return true;
}
return super.onKeyDown(keyCode, event);
}
But this hasn't worked either. Whenever I click the back button the drawer will close, but neither of these methods would be called. But once the drawer is closed, if the back button is pressed these methods will be invoked. I was also wondering if anyone knew of a simple way to handle a click outside of the drawer. I figure I could make a custom DrawerLayout and override drawerClose() or check the coordinates that are clicked on a touch event. Just curious if anyone has a simpler way.

Put this line into your code:
mDrawerLayout.setFocusableInTouchMode(false);
Then it will call your overwritten onBackPressed() when you press the back button.

Quoting myself from the question at Force EditText to lose focus when back pressed
"In my experience onBackPressed() (at least the default #Override one in an activity) will not normally fire when pushing the back button to close the keyboard. As far as I know it will only fire when a Back press would initiate a finish() on the current activity."
This probably applies the same way to the navigation drawer.
This is most likely due to the fact that the current "Activity" is not in focus when the drawer opens (same with the SoftKeyboard) so the #Override back button is not called.

I was able to solve my problem by using DrawerLayout.DrawerListener. This worked in my situation because when the back button was being pressed the drawer was still closing even though the method onBackPressed() wasn't being called.
#MH said, "The DrawerLayout (I assume that's what you're using) will consume the back button event if the drawer is opened."
Although in the documentation I could not find an explicit mention of this; there was some mention of the back button here. Unfortunately it was not of much help.
What #MH said explains why onBackPressed() was not being called when the drawer was opened, and why it was being called while it was closed.
drawerLayoutRight.setDrawerListener(this);
Where drawerLayoutRight is a DrawerLayout. And my listener looks like this:
#Override
public void onDrawerClosed(View arg0) {
if(drawerLayoutRight.getDrawerLockMode(drawerFrameRight)!= 1){
drawerLayoutRight.setDrawerLockMode(1, drawerFrameRight);
}
ExcerciseList fragment = (ExcerciseList) getFragmentManager().findFragmentById(R.id.right_drawer);
if (fragment != null) {
FragmentTransaction transaction = getFragmentManager().beginTransaction();
transaction.remove(fragment).commit();
}
}
onDrawerOpened(), onDrawerSlide() and onDrawerStateChanged() are all empty. Only one of my drawers is using the listener so I don't have to check the view.

Just simple overrede your activity or drawerlayout, will do.
#Override public boolean onKeyDown(int keyCode, KeyEvent event) {
if (KeyEvent.KEYCODE_BACK == keyCode
&& mDrawerLayout != null
&& mDrawerLayout.isDrawerOpen(leftDrawerView)) {
KeyEventCompat.startTracking(event);
return true;
}
return super.onKeyDown(keyCode, event);
}
#Override public boolean onKeyUp(int keyCode, KeyEvent event) {
if (KeyEvent.KEYCODE_BACK == keyCode
&& !event.isCanceled()
&& mDrawerToggle != null
&& mDrawerLayout.isDrawerOpen(leftDrawerView)) {
mDrawerLayout.closeDrawers();
return true;
}
return super.onKeyUp(keyCode, event);
}

The problem, as #Alex Vasilkov indicated, seems to do something with the drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED); method.
None of the suggestions above did work for me. So I wanted to write my own solution. I digged the source code of DrawerLayout Class and tried overriding onKeyDown and onKeyUp methods, but the Back Button click is not getting triggered at all, if the Lock mode is LOCK_MODE_LOCKED_CLOSED. I think this is a bug.
So in my case, I needed to lock left navigation drawer only, not the right one. And I ended up calling drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED, Gravity.START); this method to lock my left navigation drawer instead of calling drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED); this method, which locks both of the drawers and causes this back button bug.
So as a summary, drawerLayout.setDrawerLockMode(DrawerLayout.LOCK_MODE_LOCKED_CLOSED); disables back button click somehow. Maybe only if you have two navigation drawers.

After adding this line back button will manage to close DrawerLayout.
mDrawerLayout.setDescendantFocusability(ViewGroup.FOCUS_BLOCK_DESCENDANTS);

I had a very similar issue with an empty list in a fragment (wouldn't respond to back button press when the list was empty) and some of the solutions mentioned here helped me solving my issue.
The fragment causing the issue with the "onBackPressed()":
<TextView
android:id="#android:id/empty"
... />
<ListView
android:id="#android:id/list"
android:layout_width="match_parent"
android:layout_height="match_parent" />
The issue is similar in that when the list returned by the adapter is empty (#android:id/empty), the first view (TextView) doesn't seem to be "considered" as a focusable/focused view by Android (whereas the second view - ListView - is).
So pressing the back button wouldn't be registered by the view currently displayed and wouldn't be caught by my custom code in the fragment (instead closing the activity directly).
In my case, adding the following to onCreateView solved my issue (and allowed the back button press to be caught by the fragment even when the list is empty):
View view = inflater.inflate(R.layout.fragment_content, container, false);
view.setFocusableInTouchMode(true);
view.requestFocus();

I know it is a bit late but still... this answer will help others
#Override
public void onBackPressed()
{
if (mDrawerLayout.isOpen())
mDrawerLayout.close();
else
super.onBackPressed();
}

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
}