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android - 从片段中隐藏父活动底部导航不起作用

问题描述

我在父活动上加载了一个片段。该活动具有底部导航视图。我想在某个阶段隐藏底部导航。

这是我尝试做但没有工作并给出以下错误的方法。

java.lang.NullPointerException：

如果我在 Activity 本身上调用这些方法onCreate(）它工作正常。它的隐藏导航视图。

布局

<android.support.design.widget.BottomNavigationView
    android:id="@+id/navigation"
    android:layout_width="411dp"
    android:layout_height="wrap_content"
    android:background="?android:attr/windowBackground"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toBottomOf="@+id/frame_layout"
    app:menu="@menu/navigation" />

主要活动

import android.os.Bundle;
import android.support.annotation.NonNull;
import android.support.design.widget.BottomNavigationView;
import android.support.v4.app.Fragment;
import android.support.v4.view.ViewPager;
import android.support.v7.app.AppCompatActivity;
import android.view.MenuItem;
import android.view.View;

public class MainActivity extends AppCompatActivity implements BottomNavigationView.OnNavigationItemSelectedListener {

    BottomNavigationView navigation;

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

        navigation = findViewById(R.id.navigation);
        navigation.setOnNavigationItemSelectedListener(this);

        loadFragment(new LiveVideoOneFragment());

    }

    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem menuItem) {

        Fragment fragment = null;

        switch (menuItem.getItemId()) {

            case R.id.navigation_live_one:
                fragment = new LiveVideoOneFragment();
                break;

            case R.id.navigation_live_two:
                fragment = new LiveVideoTwoFragment();
                break;

            case R.id.navigation_contact:
                fragment = new ContactFragment();
                break;
        }

        return loadFragment(fragment);
    }

    private boolean loadFragment(Fragment fragment) {

        if (fragment != null) {

            getSupportFragmentManager()
                    .beginTransaction()
                    .replace(R.id.frame_layout, fragment)
                    .commit();

            return true;
        }

        return false;

    }

    public void hideBottomNavigation() {

        if (navigation.getVisibility() == View.VISIBLE) {
            navigation.setVisibility(View.GONE);
        }

    }

    public void showBottomNavigation() {
        if (navigation.getVisibility() == View.GONE) {
            navigation.setVisibility(View.VISIBLE);
        }
    }

}

分段

...

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);

    if (newConfig.orientation == Configuration.ORIENTATION_LANDSCAPE) {
        Toast.makeText(getActivity(), "Landscape", Toast.LENGTH_SHORT).show();

        View decorView = getActivity().getWindow().getDecorView();
        int uiOptions = View.SYSTEM_UI_FLAG_FULLSCREEN;
        decorView.setSystemUiVisibility(uiOptions);

        parentActivity.hideBottomNavigation();


    } else {
        Toast.makeText(getActivity(), "Portrait", Toast.LENGTH_SHORT).show();

        View decorView = getActivity().getWindow().getDecorView();
        int uiOptions = View.SYSTEM_UI_FLAG_VISIBLE;
        decorView.setSystemUiVisibility(uiOptions);

        parentActivity.showBottomNavigation();
    }
}

标签： android

解决方案

显然parentActivity是null，所以你在哪里分配它？理想情况下，您的 Fragment/Activity 交互应该通过Android 文档中概述的技术进行interface。

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