[Android] 長按選單(ContextMenu)

長按螢幕出現的選單，有點類似滑鼠右鍵選單。
不過平版或手機沒有滑鼠，所以則需要用長按的方法叫出選單。

MainActivity.java

import android.app.Activity;   
import android.os.Bundle;       
import android.view.ContextMenu;
import android.view.ContextMenu.ContextMenuInfo;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;    
import android.widget.Toast;


public class MainActivity extends Activity 
 {      
  protected static final int MENU_BUTTON_1 = Menu.FIRST;
  protected static final int MENU_BUTTON_2 = Menu.FIRST + 1;
  protected static final int MENU_BUTTON_3 = Menu.FIRST + 2;
  protected static final int MENU_BUTTON_4 = Menu.FIRST + 3;
 
    /* Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) 
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //註冊長按選單
        registerForContextMenu(findViewById(R.id.relativelayout));
                     
    }

 @Override
 public void onCreateContextMenu(ContextMenu menu, View v, ContextMenuInfo menuInfo) {
  //設定選單內容
  menu.setHeaderTitle("挑選您要的顏色"); 
  menu.add(0, MENU_BUTTON_1, 0, "紅");
  menu.add(0, MENU_BUTTON_2, 0, "橙");
  menu.add(0, MENU_BUTTON_3, 0, "黃");
  menu.add(0, MENU_BUTTON_4, 0, "綠");
 
  super.onCreateContextMenu(menu, v, menuInfo);
 }
 
 @Override
 public boolean onContextItemSelected(MenuItem item) {
  // 點選項目後,要做的事寫在這邊
  switch(item.getItemId()) {
  case MENU_BUTTON_1:
   Toast.makeText(getApplicationContext(), "您選了紅色", Toast.LENGTH_SHORT).show();
   break;
  case MENU_BUTTON_2:
   Toast.makeText(getApplicationContext(), "您選了橙色", Toast.LENGTH_SHORT).show();
   break;
  case MENU_BUTTON_3:
   Toast.makeText(getApplicationContext(), "您選了黃色", Toast.LENGTH_SHORT).show();
   break;
  case MENU_BUTTON_4:
   Toast.makeText(getApplicationContext(), "您選了綠色", Toast.LENGTH_SHORT).show();
   break;
  default:
   break;
  }
 
  return super.onContextItemSelected(item);
 }
}

我們希望在畫面任何一個地方按下去，都會出現長按選單，
所以要在這裡加入ID。如:android:id="@+id/relativelayout"
activity_main.xml

<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:id="@+id/relativelayout" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="152dp"
        android:text="請長按螢幕"
        android:textAppearance="?android:attr/textAppearanceLarge" />
  
</RelativeLayout>

結果: