片段未在底部導航視圖中加載

Question

嗨，我正在制作應用程序，在其中我使用底部導航來瀏覽片段，但是我的問題是，當我單擊該應用程序時，加載的片段在框架布局中不可見，即使當我單擊底部導航時，它也只在下面顯示空白頁是我在Google上搜索此問題的主要活動代碼，但看起來我是唯一有此問題的人

 public class MainActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener{
       FrameLayout frameLayout;
       FragmentManager fragmentManager;
       Fragment fragment;
       BottomNavigationView bottomNavigationView;


@Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);


        fragmentManager = getSupportFragmentManager();

        if(findViewById(R.id.frame_container)!=null){
            if(savedInstanceState!=null){

                return;
            }

        }
        bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_nav);
        //bottomNavigationView.setOnNavigationItemSelectedListener(this);
        //final SeekBar sb = (SeekBar) findViewById(R.id.sb);

    }


    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        Fragment fragment = null;
        switch (item.getItemId()){
            case R.id.navigation_home:
                fragment = new HomeFragment();
                loadFragment(fragment);
                return true;
            case R.id.navigation_feed:
                fragment = new FeedFragment();
                loadFragment(fragment);
                return true;
            case R.id.navigation_event:
                fragment = new EventsFragment();
                loadFragment(fragment);
                return true;
            case R.id.navigation_nearby:
                fragment = new NearbyFragment();
                loadFragment(fragment);
                return true;
            case R.id.navigation_profile:
                fragment = new ProfileFragment();
                loadFragment(fragment);
                return true;
        }

        return false;
    }


    private void loadFragment(Fragment fragment) {
        // load fragment
        //HomeFragment homeFragment = new HomeFragment();
        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
        transaction.replace(R.id.frame_container, fragment,null);
       // transaction.addToBackStack(null);
      /* Comment this line and it should work!*/
        //transaction.addToBackStack(null);
        transaction.commit();
    }

}

和我的xml

<LinearLayout android:layout_width="match_parent"
    android:layout_height="match_parent"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    android:fillViewport="true"
    android:fitsSystemWindows="true"
    android:orientation="vertical"
    xmlns:android="http://schemas.android.com/apk/res/android">

<FrameLayout
    android:id="@+id/frame_container"
    android:layout_width="match_parent"
    android:layout_height="0dp"
    android:layout_weight="1">

</FrameLayout>
    <android.support.design.widget.BottomNavigationView
        android:id="@+id/bottom_nav"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        app:menu="@menu/navigation"
        android:backgroundTint="@color/nav_color"
        app:itemIconTint="@color/bottom_nav_fore_color"
        android:background="?android:attr/windowBackground"
        android:layout_weight="0.1">

    </android.support.design.widget.BottomNavigationView>
</LinearLayout>

Answer 1

您的代碼似乎正確，請取消注釋此行，然后檢查：

  bottomNavigationView.setOnNavigationItemSelectedListener
                (new BottomNavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                        Fragment selectedFragment = null;
                        switch (item.getItemId()) {
                            case R.id.action_item1:
                                selectedFragment = ItemOneFragment.newInstance();
                                break;
                            case R.id.action_item2:
                                selectedFragment = ItemTwoFragment.newInstance();
                                break;
                            case R.id.action_item3:
                                selectedFragment = ItemThreeFragment.newInstance();
                                break;
                        }
                        FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
                        transaction.replace(R.id.frame_container, selectedFragment);
                        transaction.commit();
                        return true;
                    }
                });

希望這可以幫助 ！

刪除此：

implements BottomNavigationView.OnNavigationItemSelectedListener

Answer 2

您沒有設置setOnNavigationItemSelectedListener意味着您沒有將片段設置為底部導航抽屜，這就是為什么沒有片段在查看的原因。

首先將setOnNavigationItemSelectedListener添加setOnNavigationItemSelectedListener導航

        bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);   

然后添加以下代碼：

private BottomNavigationView.OnNavigationItemSelectedListener   mOnNavigationItemSelectedListener
        = new BottomNavigationView.OnNavigationItemSelectedListener() {

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
     Fragment fragment=null;
        switch (item.getItemId()) {
           case R.id.navigation_home:
            fragment = new HomeFragment();
            loadFragment(fragment);
            return true;
        case R.id.navigation_feed:
            fragment = new FeedFragment();
            loadFragment(fragment);
            return true;
        case R.id.navigation_event:
            fragment = new EventsFragment();
            loadFragment(fragment);
            return true;
        case R.id.navigation_nearby:
            fragment = new NearbyFragment();
            loadFragment(fragment);
            return true;
        case R.id.navigation_profile:
            fragment = new ProfileFragment();
            loadFragment(fragment);
            return true;
        }
        return false;
    }
};