1.創建Menu選單

右鍵 res > New > Android Resource Directory > Resource type 選擇 menu

右鍵 menu > New > Menu Resource File

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/developer" android:title="開發" app:showAsAction="ifRoom"/>
    <item android:id="@+id/setting" android:title="設定" app:showAsAction="ifRoom"/>
    <item android:id="@+id/save" android:title="保存"/>
    <item android:title="更多操作">
        <menu>
            <item android:id="@+id/edit" android:title="編輯" android:icon="@mipmap/ic_launcher"/>
            <item android:id="@+id/share" android:title="分享"/>
        </menu>
    </item>
</menu>

1. android:id: 唯一標示
2. android:icon：圖示
3. android:title：標題
4. android:showAsAction：顯示方式
- always：永遠顯示在menu外
- ifRoom：有空間會顯示在menu外,否則到menu中
- withText：只會顯示標題
- never：永遠顯示在menu中

2.Options Menu

//顯示menu
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
    menuInflater.inflate(R.menu.option, menu)
    return super.onCreateOptionsMenu(menu)
}

//menu監聽
override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.developer -> {
            Toast.makeText(this, "開發", Toast.LENGTH_SHORT).show()
        }
        R.id.setting -> {
            Toast.makeText(this, "設定", Toast.LENGTH_SHORT).show()
        }
        R.id.save -> {
            Toast.makeText(this, "保存", Toast.LENGTH_SHORT).show()
        }
        R.id.edit -> {
            Toast.makeText(this, "編輯", Toast.LENGTH_SHORT).show()
        }
        R.id.share -> {
            Toast.makeText(this, "分享", Toast.LENGTH_SHORT).show()
        }
    }

    return super.onOptionsItemSelected(item)
}

3.Context Menu

//註冊長按點擊顯示menu
override fun onCreate(savedInstanceState: Bundle?) {
    super.onCreate(savedInstanceState)
    setContentView(R.layout.activity_main)

    registerForContextMenu(findViewById(R.id.contextMenu))
}

//menu監聽
override fun onContextItemSelected(item: MenuItem): Boolean {
    Toast.makeText(this, "您選擇的是" + item.title, Toast.LENGTH_SHORT).show();
    return super.onContextItemSelected(item)
}

//顯示menu
override fun onCreateContextMenu(menu: ContextMenu?, v: View?, menuInfo: ContextMenu.ContextMenuInfo?) {
    menuInflater.inflate(R.menu.option, menu)
    super.onCreateContextMenu(menu, v, menuInfo)
}

4.Popup Menu

fun popMenu(view: View) {
    val menu = PopupMenu(this , view)

    menu.menuInflater.inflate(R.menu.option, menu.menu)

    //menu監聽
    menu.setOnMenuItemClickListener {
        Toast.makeText(applicationContext, it.title, Toast.LENGTH_SHORT).show()
        super.onOptionsItemSelected(it);
    }

    //顯示menu
    menu.show()
}