如何在安卓中实现选项菜单

原文:https://www . geesforgeks . org/如何实现-选项-安卓菜单/

在安卓中，有三种类型的菜单可用于定义我们的安卓应用程序中的一组选项和动作。

安卓应用程序中的菜单如下:

  • 安卓选项菜单
  • 安卓上下文菜单
  • android 弹出菜单

安卓选项菜单是安卓的主菜单。它们可以用于设置、搜索、删除项目等。该项目何时以及如何作为动作项目出现在应用程序栏中由显示动作属性决定。显示动作属性可以给出的值:

  • always: This ensures that the menu will always show in the action bar.

    语法:

    ```java app:showAsAction="always"

    ```

    示例:

    java <item         android:id="@+id/message"         android:icon="@android:drawable/ic_menu_send"         app:showAsAction="always"            android:title="message" />

  • never: This means that the menu will never show, and therefore will be available through the overflow menu

    语法:

    ```java app:showAsAction="never"

    ```

    示例:

    java <item         android:id="@+id/exit"           app:showAsAction="never"          android:title="exit"/>

下面是在安卓系统中实现选项菜单的完整代码，如下所示:

activity_main.xml

<menu 
    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" 
    tools:context=".MainActivity">

    <item
        android:id="@+id/message" 
        android:icon="@android:drawable/ic_menu_send" 
        app:showAsAction="always"   
        android:title="message"/>

    <item
        android:id="@+id/picture" 
        android:icon="@android:drawable/ic_menu_gallery" 
        app:showAsAction="always|withText" 
        android:title="picture"/>

    <item
        android:id="@+id/mode" 
        android:icon="@android:drawable/ic_menu_call" 
        app:showAsAction="always" 
        android:title="mode"/>

    <item
        android:id="@+id/about"
        android:icon="@android:drawable/ic_dialog_info" 
        app:showAsAction="never|withText"
        android:title="calculator"/>

    <item
        android:id="@+id/exit"
        app:showAsAction="never"
        android:title="exit"/>
</menu>

MainActivity.java

package com.example.menu;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

import static android.widget.Toast.LENGTH_LONG;

public class MainActivity extends AppCompatActivity {

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

    public boolean onCreateOptionsMenu(Menu menu)
    {
        getMenuInflater().inflate(R.menu.menu, menu);
        return true;
    }

    public boolean onOptionsItemSelected(MenuItem item)
    {
        switch (item.getItemId()) {
        case R.id.message:
            Toast
                .makeText(
                    getApplicationContext(),
                    "Shows share icon",
                    Toast.LENGTH_SHORT)
                .show();
            return true;

        case R.id.picture:
            Toast
                .makeText(
                    getApplicationContext(),
                    "Shows image icon",
                    Toast.LENGTH_SHORT)
                .show();
            startActivity(i2);
            return (true);

        case R.id.mode:
            Toast
                .makeText(
                    getApplicationContext(),
                    "Shows call icon",
                    Toast.LENGTH_SHORT)
                .show();
            return (true);

        case R.id.about:
            Toast
                .makeText(
                    getApplicationContext(),
                    "calculator menu",
                    Toast.LENGTH_SHORT)
                .show();
            return (true);

        case R.id.exit:
            finish();
            return (true);
        }
        return (super.onOptionsItemSelected(item));
    }
}

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