单击“上一步”按钮时，底部导航视图显示空白屏幕

Question

下面是代码：home.xml

 <androidx.coordinatorlayout.widget.CoordinatorLayout
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <FrameLayout
        android:id="@+id/bottomfrag"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_marginTop="?attr/actionBarSize"
        app:layout_behavior="@string/appbar_scrolling_view_behavior"
        />
    <com.google.android.material.bottomappbar.BottomAppBar
        android:id="@+id/bottom_app_bar"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_gravity="bottom"
        app:contentInsetStart="0dp"
        app:fabAlignmentMode="center">
        <com.rawat.soccermatch.CustomBottomNav
            android:id="@+id/bottomNavigationView"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:itemRippleColor="@android:color/transparent"
            app:labelVisibilityMode="labeled"
            app:itemIconTint="@color/enable_disable"
            app:itemTextColor="@color/enable_disable"
            app:menu="@menu/bottom_nav_menu"
            app:layout_behavior="@string/hide_bottom_view_on_scroll_behavior" />
    </com.google.android.material.bottomappbar.BottomAppBar>

    <com.google.android.material.floatingactionbutton.FloatingActionButton
        android:id="@+id/fab"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:backgroundTint="#FF9800"
        android:contentDescription="@string/title_create"
        android:src="@drawable/ic_plusn"
        app:tint="#fff"
        app:layout_anchor="@id/bottom_app_bar" />

</androidx.coordinatorlayout.widget.CoordinatorLayout>

Home.java

        bt = findViewById(R.id.bottomNavigationView);
    loadFragment(new HomeFrag()); // at first home fragment will be loaded
    bt.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            Fragment mfragment;
            int item_id=item.getItemId();
                    if(item_id==R.id.navigation_home){
                        mfragment = new HomeFrag();
                        loadFragment(mfragment);
                    }
                    else if(item_id==R.id.navigation_feed){

                        mfragment = new Feed();
                        loadFragment(mfragment);
                    }
                    else if(item_id==R.id.navigation_create){

                        mfragment = new creatematch();
                        loadFragment(mfragment);
                    }
                    else if (item_id==R.id.navigation_following){

                        mfragment = new Following();
                        loadFragment(mfragment);
                    }
                    else {

                        mfragment = new Account();
                        loadFragment(mfragment);
                    }

            return true;
        }
    });

    ft = findViewById(R.id.fab);
    ft.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            ft.setBackgroundTintList(ColorStateList.valueOf(Color.GREEN));
            ft.setRippleColor(Color.GREEN);
            Fragment fragment = new creatematch();
            bt.getMenu().findItem(R.id.navigation_create).setChecked(true);
            loadFragment(fragment);
        }
    });

}

private void loadFragment(Fragment fragment) {
    FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
    transaction.replace(R.id.bottomfrag, fragment);
    transaction.addToBackStack(null);
    transaction.commit();
}

我是不是也应该贴上HomFrag代码？

这三张照片给出了关于问题的所有信息，正如你可以看到的第一张图片显示了应用程序的启动。然后我点击其他页面，点击返回，我得到的结果在第二个图像，和第三个空白屏幕时，我再次点击返回。我不明白问题的原因，如果有谁以前遇到过这个问题，请帮助。

Answer 1

您正在将该片段添加到backstack，因此单击back detach时，需要确保未将该片段添加到backstack