AndroidToolbar应用栏使用方法简介

<Androidx.appcompat.widget.Toolbar
    android:id="@+id/toolbar"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    />

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="Http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto">
    <item android:id="@+id/back"
        android:icon="@mipmap/ic_launcher"
        android:title="Back"
        app:showAsAction="always" />
    <item android:id="@+id/delete"
        android:icon="@mipmap/ic_launcher"
        android:title="Delete"
        app:showAsAction="ifRoom" />
    <item android:id="@+id/settings"
        android:icon="@mipmap/ic_launcher"
        android:title="Settings"
        app:showAsAction="never" />
</menu>

onCreate() {
    //关联Toolbar(Manifest没有使用NoActionbar的主题会报错)
    val toolbar = findViewById<Toolbar>(R.id.toolbar)
    setSupportActionBar(toolbar)
}
//加载菜单
override fun onCreateOptionsMenu(menu: Menu?): Boolean {
    menuInflater.inflate(R.menu.toolbar, menu)
    return true
}
//处理点击事件
override fun onOptionsItemSelected(item: MenuItem): Boolean {
    when (item.itemId) {
        R.id.back -> Toast.makeText(this, "点击了back", Toast.LENGTH_SHORT).show()
        R.id.delete -> Toast.makeText(this, "点击了delete", Toast.LENGTH_SHORT).show()
        R.id.settings -> Toast.makeText(this, "点击了settings", Toast.LENGTH_SHORT).show()
    }
    return true
}