Question

嗨我正在制作应用程序，我使用底部导航来浏览片段，但我的问题是当我点击应用程序加载片段在框架布局中不可见，甚至当我点击底部导航它只是显示空白页面下面是我的主要活动代码我在谷歌搜索这个问题，但看起来我是唯一一个有这个问题的人

 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

您的代码似乎正确，取消注释此行，然后检查：

  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;
                    }
                });

希望这有帮助！

删除它：

implements BottomNavigationView.OnNavigationItemSelectedListener

Answer 2

您没有设置您的setOnNavigationItemSelectedListener表示您没有将片段设置到底部导航抽屉，说明没有片段正在查看的原因。

首先将setOnNavigationItemSelectedListener添加到bottomnavigation

        bottomNavigationView.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);

然后添加此代码 - ：

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;
    }
};

片段未加载底部导航视图

2 个答案: