How to get back from a Fragment to an Activity?

Question

I created an Activity of type Drawer Navigation and in the icons of this Activity has an action that takes me to a fragment.

My problem is that I don’t know how to come back from a fragment to an Activity ... how should I get back with the back button from onBackPressed?

I tried to simulate the back button with this but it didn’t work here:

Start fragment:

  public void showMyFragment(View V){
        Fragment fragment = null;
        fragment = new MyFragment();

        if (fragment != null) {
             FragmentManager fragmentManager = getFragmentManager();
             fragmentManager.beginTransaction()
                            .replace(R.id.frame_container, fragment)
                            .addToBackStack(null)
                            .commit();
        }   
}





@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() == 0) {
        this.finish();
    } else {
        getFragmentManager().popBackStack();
    }
}



public class MyFragment extends Fragment {

        @Override
        public View onCreateView(LayoutInflater inflater, ViewGroup container,
            Bundle savedInstanceState) {
            View v=inflater.inflate(R.layout.activity_info, null);
            return v;
        }
    }

Answer 1

A simple way to do this is to use the addToBackStack(). See how it should be:

FragmentManager fragmentManager = getSupportFragmentManager();
fragmentManager.beginTransaction().replace(R.id.flContent, fragment)
    .addToBackStack("Fragment").commit();

Thus, you can put a condition by checking whether the entry price of stack has greater value than 0. If yes, use the method popBackStack(), that will return the user to the Fragment previous, otherwise it uses the super.onBackPressed(). Behold:

@Override
public void onBackPressed() {
    if (getFragmentManager().getBackStackEntryCount() > 0 ){
        getFragmentManager().popBackStack();
    } else {
        super.onBackPressed();
    }
}

A GIF is worth a thousand images:

This project is saved as navDrawer on Github.

Answer 2

When using addToBackStack(null) is including Fragments in navigation, causing the "Back Button" to display the Fragment previous.

If you don’t want to sail back between the Fragments open do not add to transanction at the backstack. Do not use addToBackStack(null).

Alter

fragmentManager.beginTransaction()
               .replace(R.id.frame_container, fragment)
               .addToBackStack(null)
               .commit();

for

fragmentManager.beginTransaction()
               .replace(R.id.frame_container, fragment)
               .commit();

However, if you want to keep browsing between Fragments and at the same time give the possibility to return to the previous Activity, you have to implement the "Up Button".

Follow the following steps:

• State what the Activity parent of each Activity is. This is done on Androidmanifist.xml using the attribute android:parentActivityName:

  <application ... >
      ...
  
      <!-- A main/home activity (não tem uma activity pai) -->
  
      <activity
          android:name="com.example.myfirstapp.MainActivity" ...>
          ...
      </activity>
  
      <!-- Uma activity filha da main activity -->
      <activity
          android:name="com.example.myfirstapp.MyChildActivity"
          android:label="@string/title_activity_child"
          android:parentActivityName="com.example.myfirstapp.MainActivity" >
  
          <!-- meta-data para suportar Android 4.0 ou inferior -->
          <meta-data
              android:name="android.support.PARENT_ACTIVITY"
              android:value="com.example.myfirstapp.MainActivity" />
      </activity>
  </application>
  

• Make "Up Button" available/visible

  @Override
  public void onCreate(Bundle savedInstanceState) {
      ...
      getActionBar().setDisplayHomeAsUpEnabled(true);
  }
  

• Use the static method navigateUpFromSameTask(), de Navutils, to navigate to the parent Activity:

  @Override
  public boolean onOptionsItemSelected(MenuItem item) {
      switch (item.getItemId()) {
      // Respond to the action bar's Up/Home button
      case android.R.id.home:
          NavUtils.navigateUpFromSameTask(this);
          return true;
      }
      return super.onOptionsItemSelected(item);
  }
  

For more information see Providing Up Navigation, in the documentation.

Other topics to read:

• Navigation with Back and Up.
• Implementing Effective Navigation.