如何在 Android Studio 中的片段中实现背压

Question

I want that whenever the user presses back in any fragment, user will moved into main activity.

MainActivity.java

 package com.thechamp.ait; import androidx.annotation.NonNull; import androidx.annotation.RequiresApi; import androidx.appcompat.app.ActionBar; import androidx.appcompat.app.ActionBarDrawerToggle; import androidx.appcompat.app.AppCompatActivity; import android.os.Build; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.accessibility.AccessibilityRecord; import android.widget.Toast; import androidx.appcompat.widget.Toolbar; import androidx.core.view.GravityCompat; import androidx.drawerlayout.widget.DrawerLayout; import com.google.android.material.navigation.NavigationView; import java.security.MessageDigest; import java.util.Calendar; public class MainActivity extends AppCompatActivity implements NavigationView.OnNavigationItemSelectedListener { private DrawerLayout drawerLayout; private NavigationView navigationView; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); Toolbar toolbar = findViewById(R.id.toolbar); setSupportActionBar(toolbar); getSupportActionBar().setTitle(null); getSupportActionBar().setElevation(0); navigationView = findViewById(R.id.nav_view); navigationView.setItemIconTintList(null); Calendar c = Calendar.getInstance(); int timeOfDay = c.get(Calendar.HOUR_OF_DAY); if(timeOfDay >= 0 && timeOfDay < 12){ Toast.makeText(this, "Good Morning", Toast.LENGTH_SHORT).show(); }else if(timeOfDay >= 12 && timeOfDay < 16){ Toast.makeText(this, "Good Afternoon", Toast.LENGTH_SHORT).show(); }else if(timeOfDay >= 16 && timeOfDay < 21){ Toast.makeText(this, "Good Evening", Toast.LENGTH_SHORT).show(); }else if(timeOfDay >= 21 && timeOfDay < 24){ Toast.makeText(this, "Good Night", Toast.LENGTH_SHORT).show(); } drawerLayout = findViewById(R.id.drawer_layout); navigationView.setNavigationItemSelectedListener(this); ActionBarDrawerToggle toggle = new ActionBarDrawerToggle(this, drawerLayout, toolbar, R.string.navigation_drawer_open, R.string.navigation_drawer_close); drawerLayout.addDrawerListener(toggle); toggle.syncState(); } @Override public boolean onNavigationItemSelected( MenuItem item) { switch (item.getItemId()) { case R.id.nav_about: getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new AboutCollege()).commit(); break; case R.id.nav_Earnmoney: getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new EarnMoney()).commit(); break; case R.id.nav_Feedback: getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new Feedback()).commit(); break; case R.id.nav_notice: getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new NoticeBoard()).commit(); break; case R.id.nav_study: getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new StudyMaterial()).commit(); break; case R.id.nav_support: getSupportFragmentManager().beginTransaction().replace(R.id.fragment_container, new Support()).commit(); break; } drawerLayout.closeDrawer(GravityCompat.START); return true; } @Override public void onBackPressed() { if (drawerLayout.isDrawerOpen(GravityCompat.START)) { drawerLayout.closeDrawer(GravityCompat.START); } else { super.onBackPressed(); } }}

and here Feedback Fragment code - I want that whenever user press back button then user moved to main activity.

 package com.thechamp.ait; import android.os.Bundle; import android.view.LayoutInflater; import android.view.View; import android.view.ViewGroup; import android.widget.LinearLayout; import androidx.annotation.NonNull; import androidx.annotation.Nullable; import androidx.appcompat.app.AppCompatActivity; import androidx.fragment.app.Fragment; public class Feedback extends Fragment { @Nullable @Override public View onCreateView(@NonNull LayoutInflater inflater, @Nullable ViewGroup container, @Nullable Bundle savedInstanceState) { View view = inflater.inflate(R.layout.fragment_feedback, container, false); ((AppCompatActivity) getActivity()).getSupportActionBar().hide(); return view; } }

Answer 1

    override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    activity?.onBackPressedDispatcher?.addCallback(this, object : OnBackPressedCallback(true) {
        override fun handleOnBackPressed() {
          if(shouldInterceptBackPress()){
            // your logic when backpress is clicked
          }else{
            isEnabled = false
            main.activity?.onBackPressed()
          }
        }
    })
}

Check From Android Documantation