Android onCreateOptionsMenu findItem 获取空值

Question

我是 android 开发的新手。我使用 android studio 默认项目模板 Navigation Drawer Activity.

创建了一个新项目

我添加了如下调试消息：

public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.main, menu);

    MenuItem navCamera = menu.findItem(R.id.nav_camera);

    if(navCamera != null) {
        Log.d("MainActivity", "Not null");
    }

    return true;
}

为什么我无法获取菜单项对象？

Main.xml

<menu xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
<item
    android:id="@+id/action_settings"
    android:orderInCategory="100"
    android:title="@string/action_settings"
    app:showAsAction="never" />

activity_main_drawer.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">

<group android:checkableBehavior="single">
    <item
        android:id="@+id/nav_camera"
        android:icon="@drawable/ic_menu_camera"
        android:title="Import" />
    <item
        android:id="@+id/nav_gallery"
        android:icon="@drawable/ic_menu_gallery"
        android:title="Gallery" />
    <item
        android:id="@+id/nav_slideshow"
        android:icon="@drawable/ic_menu_slideshow"
        android:title="Slideshow" />
    <item
        android:id="@+id/nav_manage"
        android:icon="@drawable/ic_menu_manage"
        android:title="Tools" />
</group>

<item android:title="Communicate">
    <menu>
        <item
            android:id="@+id/nav_share"
            android:icon="@drawable/ic_menu_share"
            android:title="Share" />
        <item
            android:id="@+id/nav_send"
            android:icon="@drawable/ic_menu_send"
            android:title="Send" />
    </menu>
</item>

</menu>

Answer 1

如果您想使用菜单项，请使用 onNavigationItemSelected 函数，如下所示。

@Override
public boolean onNavigationItemSelected(MenuItem item) {

    int id = item.getItemId();

    switch (id) {
        R.id.nav_camera:
            Log.d("MainActivity", "Not null");
        break;
    }
}

和onCreateOptionsMenu如下：

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.dashboard, menu);
    return true;
}

Answer 2

抱歉上面的回答，我没有完全阅读你的问题。您可以在 onCreate() 中找到 NavigationView 并使用您的库设置图标

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ...
    //other stuff here
    ...
    NavigationView navigationView = (NavigationView) findViewById(R.id.nav_view);

    // get menu from navigationView
    Menu menu = navigationView.getMenu();

    // find MenuItem you want to change
    MenuItem nav_camara = menu.findItem(R.id.nav_camara);

    // set new title to the MenuItem
    nav_camara.setTitle("NewTitleForCamera");
    // Set your icon menu here

    // do the same for other MenuItems
    ....

    // add NavigationItemSelectedListener to check the navigation clicks
    navigationView.setNavigationItemSelectedListener(this);

}

Android onCreateOptionsMenu findItem 获取空值

Android onCreateOptionsMenu findItem get null

android

menu

menuitem

oncreateoptionsmenu