按下设备后退按钮或工具栏后退箭头时如何显示警报对话框或对话框

Question

I am using navigation component, and when I use device back button or toolbar back arrow I want to show alert dialog or custom dialog before navigate to previous fragment, if user press yes then navigate to the previous fragment, anything else dismiss like a dialog functionality. I already tried this:

OnBackPressedCallback callback = new OnBackPressedCallback(true /* enabled by default */) {

    @Override
    public void handleOnBackPressed() {
        // Handle the back button event
    }
};

this is my code for fragment and actions and i asked to how to handle the backarrow event or callback in navigation component architecture so as i move to previous fragment so before going to back it will display a alert are you sure to move from here like that.

  <fragment
        android:id="@+id/drawOnImageFragment"
        android:name="com.consulthealthcare.app.fragments.DrawOnImageFragment"
        android:label="Mark on Prescription"
        tools:layout="@layout/fragment_draw_on_image">
        <argument
            android:name="uri"
            app:argType="string" />
        <action
            android:id="@+id/action_drawOnImageFragment_to_confirmOrderFragment"
            app:destination="@id/confirmOrderFragment"
            app:enterAnim="@anim/enter_from_right"
            app:exitAnim="@anim/exit_to_left"
            app:popEnterAnim="@anim/enter_from_left"
            app:popExitAnim="@anim/exit_to_right" />
        <action
            android:id="@+id/action_drawOnImageFragment_to_dialogNavFragment"
            app:destination="@id/dialogNavFragment" />
    </fragment>

requireActivity().getOnBackPressedDispatcher().addCallback(this, callback);

This worked for the device back button but not for the navigation component toolbar back arrow.

Answer 1

on back button you have to override the onbackpress method and inside it you would write your custom alert dialog something like this:

 @Override
    public void onBackPressed()
    {
  
        // Create the object of
        // AlertDialog Builder class
        AlertDialog.Builder builder
            = new AlertDialog
                  .Builder(context/* requireActivity() in fragment*/ );
  
        // Set the message show for the Alert time
        builder.setMessage("Do you want to go back ?");
  
        // Set Alert Title
        builder.setTitle("Alert !");
  
        // Set Cancelable false
        // for when the user clicks on the outside
        // the Dialog Box then it will remain show
        builder.setCancelable(false);
  
        // Set the positive button with yes name
        // OnClickListener method is use of
        // DialogInterface interface.
  
        builder
            .setPositiveButton(
                "Yes",
                new DialogInterface
                    .OnClickListener() {
  
                        @Override
                        public void onClick(DialogInterface dialog,
                                            int which)
                        {
  
                            // write what you want to do here for yes
                        }
                    });
  
        // Set the Negative button with No name
        // OnClickListener method is use
        // of DialogInterface interface.
        builder
            .setNegativeButton(
                "No",
                new DialogInterface
                    .OnClickListener() {
  
                        @Override
                        public void onClick(DialogInterface dialog,
                                            int which)
                        {
  
                            // If user click no
                            // then dialog box is canceled.
                            dialog.cancel();
                        }
                    });
  
        // Create the Alert dialog
        AlertDialog alertDialog = builder.create();
  
        // Show the Alert Dialog box
        alertDialog.show();
    }

and for back arrow same concept I would suggest to write a method for back arrow and back button contains the alert and call it when these button pressed

Answer 2

finally i have done the navigation component toolbar back arrow using

 binding.toolbar.setNavigationOnClickListener(this);

  @Override
    public void onClick(View v) {
        NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.navHostFragment);
        Fragment fragment = navHostFragment.getChildFragmentManager().getFragments().get(0);
        if (fragment instanceof HostFragment) {
            if (binding.drawerLayout.isDrawerOpen(GravityCompat.START)) {
                binding.drawerLayout.closeDrawer(GravityCompat.START, true);
            } else {
                binding.drawerLayout.openDrawer(GravityCompat.START, true);
            }
        } else {
            navController.navigateUp();
        }
    }

this line make the default functionality of the navigation

 navController.navigateUp();