隐藏片段中的父活动底部导航不起作用

Question

我在父活动上加载了一个片段。该活动具有“底部导航”视图。我想在特定阶段隐藏“底部导航”。

这是我尝试执行的操作，但是不起作用，并出现以下错误。

  

java.lang.NullPointerException：

如果我在Activity本身onCreate(上调用这些方法，则可以正常工作。隐藏的导航视图。

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" />

MainActivity

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);
        }
    }

}

片段

...

@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();
    }
}

Answer 1

显然[' START 100', " SUB =X'1D'", ' LTORG', "=X'1D' BYTE X'1D'", ' RESW 20', " SUB =X'0259'", " ADD =C'12345'", " MUL =X'4356'", " SUB =X'69'", ' LTORG', "=X'0259' BYTE X'0259'", "=C'12345' BYTE C'12345'", "=X'4356' BYTE X'4356'", "=X'69' BYTE X'69'", " ADD =C'05'", ' END EXA'] 是parentActivity，那么您将其分配到哪里？理想情况下，您的片段/活动交互应该通过Android Documentation中概述的技术通过null进行。

Answer 2

我看不到您在哪里声明或分配parentActivity变量。有一种简单的方法可以从片段中调用MainActivity中的方法。

@Override
public void onConfigurationChanged(Configuration newConfig) {
    super.onConfigurationChanged(newConfig);
    Toast.makeText(getActivity(), "onConfigurationChanged", Toast.LENGTH_SHORT).show();
    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);

        // Comment-out this line
        // parentActivity.hideBottomNavigation();

        // Add this line
        ((MainActivity)requireActivity()).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);

        // Comment-out this line
        // parentActivity.showBottomNavigation();

        // Add this line
        ((MainActivity)requireActivity()).showBottomNavigation();
    }
}