按钮出现在 BottomNavigationView

创建BottomTabActivity和一个带有 xml 文件的片段。我连接了所有这些，当我在片段的 xml 文件中创建一个常规按钮时，它会出现在这个 BottomTab 中，无论我放在哪里。我不知道怎么了。

 MainActivity.xml

<?xml version="1.0" encoding="utf-8"?>
  <android.support.constraint.ConstraintLayout  xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:id="@+id/container"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".MainActivity">

<android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="0dp"
    android:layout_height="wrap_content"
    android:background="?android:attr/windowBackground"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintLeft_toLeftOf="parent"
    app:layout_constraintRight_toRightOf="parent"
    app:menu="@menu/navigation" />

</android.support.constraint.ConstraintLayout>


  MainActivity.class



public class MainActivity extends AppCompatActivity {



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

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.navigation_home:
                  account account = new account();
                FragmentManager manager = getSupportFragmentManager();
                manager.beginTransaction().replace(R.id.navigation, account, account.getTag()).commit();
                return true;
            case R.id.navigation_dashboard:

                return true;
            case R.id.navigation_notifications:

                return true;
        }
        return false;
    }
};

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


    BottomNavigationView navigation = (BottomNavigationView) findViewById(R.id.navigation);
    navigation.setOnNavigationItemSelectedListener(mOnNavigationItemSelectedListener);
}

}