How to detect when back button pressed in fragment android?

Question

I have project with navigation drawer with fragment, with 5 menu, the problem is when i go to menu 4 and the i press the back button the app closed, but i need the app back to first menu which is all the menu in fragment.

This is code for Main Activity (Navigation Drawer)

public class MainActivity extends AppCompatActivity{
DrawerLayout mDrawerLayout;
NavigationView mNavigationView;
FragmentManager mFragmentManager;
FragmentTransaction mFragmentTransaction;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    /**
     *Setup the DrawerLayout and NavigationView
     */

    mDrawerLayout = (DrawerLayout) findViewById(R.id.drawerLayout);
    mNavigationView = (NavigationView) findViewById(R.id.shitstuff) ;

    /**
     * Lets inflate the very first fragment
     * Here , we are inflating the TabFragment as the first Fragment
     */

    mFragmentManager = getSupportFragmentManager();
    mFragmentTransaction = mFragmentManager.beginTransaction();
    mFragmentTransaction.replace(R.id.containerView,new Recommendation()).commit();
    /**
     * Setup click events on the Navigation View Items.
     */

    mNavigationView.setNavigationItemSelectedListener(new NavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(MenuItem menuItem) {
            mDrawerLayout.closeDrawers();



            if (menuItem.getItemId() == R.id.nav_item_lux_level_recomen) {
                FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
                fragmentTransaction.replace(R.id.containerView,new Recommendation()).commit();

            }

            if (menuItem.getItemId() == R.id.nav_item_room_index_calc) {
                FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
                xfragmentTransaction.replace(R.id.containerView,new RoomIndex()).commit();
            }

            if (menuItem.getItemId() == R.id.nav_item_utilization_factor_calc) {
                FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
                xfragmentTransaction.replace(R.id.containerView,new UtilizationFactorCalculator()).commit();
            }

            if (menuItem.getItemId() == R.id.nav_item_conversions) {
                FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
                xfragmentTransaction.replace(R.id.containerView,new Conversion()).commit();
            }
            if (menuItem.getItemId() == R.id.nav_item_lux) {
                FragmentTransaction xfragmentTransaction = mFragmentManager.beginTransaction();
                xfragmentTransaction.replace(R.id.containerView,new LuxSensor()).commit();
            }


            return false;
        }

    });

    /**
     * Setup Drawer Toggle of the Toolbar
     */

    android.support.v7.widget.Toolbar toolbar = (android.support.v7.widget.Toolbar) findViewById(R.id.toolbar);
    ActionBarDrawerToggle mDrawerToggle = new ActionBarDrawerToggle(this,mDrawerLayout, toolbar,R.string.app_name,
            R.string.app_name);

    mDrawerLayout.setDrawerListener(mDrawerToggle);

    mDrawerToggle.syncState();




}

This one of the Menu (Fragment)

public class LuxSensor extends Fragment {
TextView textLIGHT_available, textLIGHT_reading;
FragmentManager mFragmentManager;
@Nullable
@Override
public View onCreateView(LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) {
    View x =  inflater.inflate(R.layout.lux_sensor,null);
    textLIGHT_reading
            = (TextView)x.findViewById(R.id.LIGHT_reading);

    SensorManager mySensorManager = (SensorManager)getActivity().getSystemService(Context.SENSOR_SERVICE);

    Sensor LightSensor = mySensorManager.getDefaultSensor(Sensor.TYPE_LIGHT);
    if(LightSensor != null){
        mySensorManager.registerListener(
                LightSensorListener,
                LightSensor,
                SensorManager.SENSOR_DELAY_NORMAL);

    }else{
        textLIGHT_available.setText("Sensor.TYPE_LIGHT NOT Available");
    }
    FragmentManager fm = getFragmentManager();

    return x;
}





private final SensorEventListener LightSensorListener
        = new SensorEventListener(){

    @Override
    public void onAccuracyChanged(Sensor sensor, int accuracy) {
        // TODO Auto-generated method stub

    }

    @Override
    public void onSensorChanged(SensorEvent event) {
        if(event.sensor.getType() == Sensor.TYPE_LIGHT){
            textLIGHT_reading.setText(event.values[0]+" LUX");
        }
    }

};

}

I have tried solution in internet but it still closed

make an function in fragment and call it from onBackpressed() from activity using fragment object. — Jaydeep Devda, Mar 17 '17 at 13:51
my answer should be the accepted one. it provides the perfect solution to this problem. — Abhilash Das, Sep 13 '21 at 13:56

score 13 · Answer 1 · answered Mar 17 '17 at 14:11

In fragment you should use something like this:

  @Override
    //Pressed return button - returns to the results menu
    public void onResume() {
        super.onResume();
        getView().setFocusableInTouchMode(true);
        getView().requestFocus();
        getView().setOnKeyListener(new View.OnKeyListener() {
            @Override
            public boolean onKey(View v, int keyCode, KeyEvent event) {

                if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK){

                 //your code

                   return true;
                }
                return false;
            }
        });
    }

When the keyboard is open, I have to click twice to execute my code. — Nikhil Aggala, May 09 '20 at 05:57

score 12 · Answer 2 · edited Apr 18 '22 at 04:53

12

onCreateView of fragment add this

Java

requireActivity().getOnBackPressedDispatcher().addCallback(activity, new OnBackPressedCallback(true) {
    @Override
    public void handleOnBackPressed() {
        // in here you can do logic when backPress is clicked
    }
});

Kotlin

requireActivity().onBackPressedDispatcher.addCallback(object : OnBackPressedCallback(true) {
    override fun handleOnBackPressed() {
        // in here you can do logic when backPress is clicked
    }
})

edited Apr 18 '22 at 04:53

Aditya vikram Shekhawat

66
2
5

answered Jun 19 '20 at 12:32

Deeptimay Routray

166
1
6

this code goes in loop – D_K Aug 19 '22 at 10:39
Yes this method is clearly the best way since onBackPressed is deprecated. But this callback handle the event. What if I just want to be aware of the event and not handle it ? – Marine Droit Oct 19 '22 at 14:23

score 6 · Answer 3 · answered Mar 17 '17 at 13:53

6

In main activity you need to override the following function

@Override
public void onBackPressed()
{
     // code here to check what fragment you are on and handle that accordingly
     super.onBackPressed();  // this exits the app.
}

Documentation is available here: https://developer.android.com/reference/android/app/Activity.html#onBackPressed()

answered Mar 17 '17 at 13:53

Menachem Hornbacher

2,080
2
24
36

1

For ***"code .. to check what fragment you are on"*** - see `getActiveFragment()` here: https://stackoverflow.com/a/15543580/2162226 – Gene Bo Aug 09 '17 at 04:40

score 4 · Accepted Answer · answered Mar 17 '17 at 14:04

4

In your MainActivity

@Override
public void onBackPressed()
{
    FragmentTransaction fragmentTransaction = mFragmentManager.beginTransaction();
    fragmentTransaction.replace(R.id.containerView,new Recommendation()).commit();
}

answered Mar 17 '17 at 14:04

jorgeavilae

208
1
9

score 3 · Answer 5 · answered Sep 22 '20 at 09:28

use this (in kotlin)

activity?.onBackPressedDispatcher?.addCallback(this, object : OnBackPressedCallback(true) {
override fun handleOnBackPressed() {
    // in here you can do logic when backPress is clicked
}

})

i think this is the most elegant way to do it

score 0 · Answer 6 · answered Mar 17 '17 at 14:00

0

You can key press listener in android using setOnKeyListener(). And then, if you want to handle the back press, override the onKey method :

@Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
    if (event.getAction() == KeyEvent.ACTION_UP && keyCode == KeyEvent.KEYCODE_BACK) {
         // do your thing
    }

}

answered Mar 17 '17 at 14:00

Yash

5,225
4
32
65

2

The back button doesn't send a key event, it calls into onBackPressed instead. – Gabe Sechan Mar 17 '17 at 14:01
@GabeSechan: IMO, it works. I've tested this in Dialog Fragment, so it should work in fragment also. – Yash Mar 17 '17 at 14:08
2

It doesn't work. It hasn't worked since 2010. The back and home buttons are not capturable via onKeyPressed. If you found a place where it does, its either a bug or a weird version of the OS from an OEM. – Gabe Sechan Mar 17 '17 at 14:10
okay, I didn't know if it's 'supposed' to work or not. But I just tested in my dialog fragment. It indeed works. My device is : gennymotion emulator, running android 6. – Yash Mar 17 '17 at 18:11
1

I checked again, it works in `DialogFragment` but not in `Fragment`. Any explanation? – Yash Mar 21 '17 at 05:22

score 0 · Answer 7 · answered Oct 19 '22 at 14:34

Now the onBackPressed method is deprecated and we need to use this way (much simpler !):

override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    activity?.onBackPressedDispatcher?.addCallback(this, object : OnBackPressedCallback(true) {
        override fun handleOnBackPressed() {
          if(shouldInterceptBackPress()){
            // in here you can do logic when backPress is clicked
          }else{
            isEnabled = false
            activity?.onBackPressed()
          }
        }
    })
}

You can found full explanation here With this example it shows how to do when you are not sure that you need to consume the back press event

How to detect when back button pressed in fragment android?

7 Answers7

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