Android使用PopupWindow創建一個簡單的菜單

PopupWindow是一個彈出式窗口，它可以展示任意View。他會浮在當前窗口的上方展示。

下面看代碼：

    public class MyActivity extends Activity  
    {  
        private PopupWindow menu;  
        private LayoutInflater inflater;  
        private View layout;  

        @Override  
        public void onCreate(Bundle savedInstanceState)  
        {  
            super.onCreate(savedInstanceState);  
            setContentView(R.layout.main);  
            //實例化PopupWindow創建菜單  
            initMenu();  
        }  

        //判斷按鍵 菜單的顯示與隱藏  
        @Override  
        public boolean onKeyDown(int keyCode, KeyEvent event) {  
            if(!menu.isShowing()&&keyCode == KeyEvent.KEYCODE_MENU){  
               show();  
            }else{  
                menu.dismiss();  
            }  
            if(keyCode == KeyEvent.KEYCODE_BACK&&menu.isShowing()){  
                menu.dismiss();  
            }  
            return true;  
        }  
        //實例化PopupWindow創建菜單  
        private void initMenu(){  

                //獲取LayoutInflater實例  
                inflater  = (LayoutInflater) this.getSystemService(LAYOUT_INFLATER_SERVICE);  
                //獲取彈出菜單的布局  
                layout = inflater.inflate(R.layout.menu,null);  
                //設置popupWindow的布局  
                menu = new PopupWindow(layout, WindowManager.LayoutParams.WRAP_CONTENT,WindowManager.LayoutParams.WRAP_CONTENT);  

        }  

        //顯示菜單  
        private void show(){  
               //設置位置  
                menu.showAtLocation(this.findViewById(R.id.main), Gravity.BOTTOM|Gravity.CENTER_HORIZONTAL,0,0); //設置在屏幕中的顯示位置  
        }  
    }  

菜單的布局文件：

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
              android:layout_width="fill_parent"
              android:layout_height="fill_parent"
              android:orientation="horizontal"
        >
    <ImageView
        android:id="@+id/icon_1"
        android:background="@drawable/icon_1"
        android:layout_width="40dp"
        android:layout_height="40dp"/>
    <ImageView
        android:id="@+id/icon_2"
        android:background="@drawable/icon_2"
        android:layout_width="40dp"
        android:layout_height="40dp"/>
    <ImageView
        android:id="@+id/icon_3"
        android:background="@drawable/icon3"
        android:layout_width="40dp"
        android:layout_height="40dp"/>
    <ImageView
        android:id="@+id/icon_4"
        android:background="@drawable/icon4"
        android:layout_width="40dp"
        android:layout_height="40dp"/>

</LinearLayout>