[Android] Context Menu

最近看到一個蠻特別的東西--Context Menu--，沒想到可以這樣用，
幫Button加入"長按"選單




首先這是MainActivity的layout，XML的部份，只有一個Button

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context="com.example.boywhychen.context_menu.MainActivity">

    <Button
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:id="@+id/menu_btn"
        android:text="Context Menu" />
</RelativeLayout>

接下來我們需要在menu資料來下建立一個my_menu.xml


內容就是列出Menu中要顯示的Item內容以及順序

<?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/color_blue"
    android:title="Blue"
    android:orderInCategory="1"
    app:showAsAction="ifRoom"/>
<item android:id="@+id/color_red"
    android:title="Red"
    android:orderInCategory="2"
    app:showAsAction="ifRoom"/>
<item android:id="@+id/color_green"
    android:title="Green"
    android:orderInCategory="3"
    app:showAsAction="ifRoom"/>
</menu>

接下來是主程式

package com.example.boywhychen.context_menu;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.ContextMenu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity {



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

        //初始化Button
        Button menu_btn=(Button)findViewById(R.id.menu_btn);
        //幫Button註冊ContextMenu
        registerForContextMenu(menu_btn);
    }


    @Override
     public void onCreateContextMenu(ContextMenu menu, View v, ContextMenu.ContextMenuInfo menuInfo) {
        super.onCreateContextMenu(menu, v, menuInfo);
        //要使用的Context Menu XML檔案
        getMenuInflater().inflate(R.menu.my_menu,menu);
    }

    @Override
    public boolean onContextItemSelected(MenuItem item) {
        //按下Context Menu Item要做的事
        switch ((item.getItemId()))
        {
            case R.id.color_blue:
                Toast.makeText(MainActivity.this,"Blue",Toast.LENGTH_SHORT).show();
                break;
            case R.id.color_green:
                Toast.makeText(MainActivity.this,"Green",Toast.LENGTH_SHORT).show();
                break;
            case R.id.color_red:
                Toast.makeText(MainActivity.this,"Red",Toast.LENGTH_SHORT).show();
                break;
        }

        return super.onContextItemSelected(item);
    }
}

執行效果（記住是長按才會跳出選單～我一開始都用click都沒反應～搞了半天）

點下Red後，Toast會顯示你按下的是Red




參考來源：

The Complete Android Material Design Course: Become a Pro
https://www.udemy.com/android-material-design-course-tutorial/learn/v4/overview
上課心得筆記一下