Menu菜单

常用的菜单

菜单	显示菜单	事件监听
系统菜单	onCreateOptionsMenu	onOptionsItemSelected
上下文菜单	AlertDialog.Builder()	setSingleChoiceItems()

系统菜单

步骤

1.在res下面创建一个menu文件夹，并新建一个xml文件作为OptionMenu的布局文件

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/red" android:title="红色"></item>
    <item android:id="@+id/blue" android:title="蓝色"></item>
    <item android:id="@+id/green" android:title="绿色"></item>
</menu>

2.Activity重写onCreateOptionsMenu加载资源文件
3.Activity重写onOptionsItemSelected加设置事件监听

package com.example.day02_homework;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        getMenuInflater().inflate(R.menu.option_menu,menu);
        return super.onCreateOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.red:
                Toast.makeText(this, item.getTitle(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.blue:
                Toast.makeText(this, item.getTitle(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.green:
                Toast.makeText(this, item.getTitle(), Toast.LENGTH_SHORT).show();
                break;
        }
        return super.onOptionsItemSelected(item);
    }
}

注意：一个Activity只有一个系统菜单

上下文菜单ContextMenu

1.在res下面创建一个menu文件夹，并新建一个xml文件作为ContextMenu的布局文件，我们复用上面的menu布局
2.Activity重写onCreateConextMenu加载资源文件
3.Activity重写onConextItemSelected设置事件监听
4.为控件添加长按属性并将菜单绑定到这个控件上：registerForContextMenu(控件)

package com.example.day02_homework;

import androidx.annotation.NonNull;
import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.ContextMenu;
import android.view.MenuItem;
import android.view.View;
import android.widget.TextView;
import android.widget.Toast;

public class Main2Activity extends AppCompatActivity {

    private TextView textId;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main2);

        textId = (TextView) findViewById(R.id.text_id);

        registerForContextMenu(textId);
    }

    @Override
    public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        getMenuInflater().inflate(R.menu.option_menu,menu);
        super.onCreateContextMenu(menu, v, menuInfo);
    }

    @Override
    public boolean onContextItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.blue:
                Toast.makeText(this, item.getTitle(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.red:
                Toast.makeText(this, item.getTitle(), Toast.LENGTH_SHORT).show();
                break;
            case R.id.green:
                Toast.makeText(this, item.getTitle(), Toast.LENGTH_SHORT).show();
                break;
        }
        return super.onContextItemSelected(item);
    }
}

弹出菜单

步骤1：在res下面创建一个menu文件夹，并新建一个xml文件作为PoupMenu的布局文件。
步骤2：把PopupMenu相关逻辑封装到showPopupMenu()方法中，包含PopupMenu的实例化、布局设置、显示、添加MenuItem的点击监听及响应等
步骤3：为控件设置事件监听直接调用showPopupMenu()方法

package com.example.day02_homework;

import androidx.appcompat.app.AppCompatActivity;

import android.os.Bundle;
import android.view.MenuItem;
import android.view.View;
import android.widget.PopupMenu;
import android.widget.PopupWindow;
import android.widget.TextView;
import android.widget.Toast;

public class Main3Activity extends AppCompatActivity {

    private TextView textId;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main3);

        textId = (TextView) findViewById(R.id.text_id);
        textId.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                showPopupMenu(view);
            }
        });

    }

    private void showPopupMenu(View view) {
        PopupMenu popupMenu = new PopupMenu(this, view);
        popupMenu.inflate(R.menu.option_menu);
        popupMenu.setOnMenuItemClickListener(new PopupMenu.OnMenuItemClickListener() {
            @Override
            public boolean onMenuItemClick(MenuItem menuItem) {
                switch (menuItem.getItemId()) {
                    case R.id.blue:
                        Toast.makeText(Main3Activity.this, menuItem.getTitle(), Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.red:
                        Toast.makeText(Main3Activity.this, menuItem.getTitle(), Toast.LENGTH_SHORT).show();
                        break;
                    case R.id.green:
                        Toast.makeText(Main3Activity.this, menuItem.getTitle(), Toast.LENGTH_SHORT).show();
                        break;
                }
                return false;
            }
        });
        popupMenu.show();
    }
}

注意：弹出菜单，默认弹出的位置在控件view的下方