【Android】Menu不同選單的使用介紹

• 這是使用inflater XML的方式來建立一個Menu.顯然我們需要在res/menu/的目錄下建立類似下面的一個檔案：

<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/new_game" android:icon="@drawable/ic_new_game" android:title="@string/new_game" /> <item android:id="@+id/help" android:icon="@drawable/ic_help" android:title="@string/help" /> </menu> android:id A resource ID that's unique to the item, which allows the application can recognize the item when the user selects it. android:icon A reference to a drawable to use as the item's icon. android:title A reference to a string to use as the item's title.除了上面三個屬性外，更多的我們可以參考Menu Resource

• Inflating a Menu Resource

@Override public boolean onCreateOptionsMenu(Menu menu) { MenuInflater inflater = getMenuInflater(); inflater.inflate(R.menu.game_menu, menu); return true; }在3.0之前會預設顯示6個items,如果超出6個,最後一個就用more來顯示，點選more會顯示其餘的items.

3.0之前onCreateOptionsMenu是在第一次點選menu的時候被呼叫到，而3.0之後是在activity被建立的時候就被呼叫了

當點選menu按鍵的時候會call 到onCreateOptionsMenu.

• 當使用者點選其中的item的適合會call到下面的方法：

@Override public boolean onOptionsItemSelected(MenuItem item) { // Handle item selection switch (item.getItemId()) { case R.id.new_game: newGame(); return true; case R.id.help: showHelp(); return true; default: return super.onOptionsItemSelected(item); } }

• 根據AP執行情況來調整Menu的Item

On Android 2.3 and lower, the system callsonPrepareOptionsMenu()each time the user opens the Options Menu.

On Android 3.0 and higher, you must callinvalidateOptionsMenu()when you want to update the menu, because the menu is always open. The system will then callonPrepareOptionsMenu()so you can update the menu items.

【2】建立Context Menu

For example:

If your activity uses aListViewand you want all list items to provide a context menu, register all items for a context menu by passing theListViewtoregisterForContextMenu(). For example, if you're using aListActivity, register all list items like this:registerForContextMenu(getListView());

【3】Creating Submenus

<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/file" android:icon="@drawable/file" android:title="@string/file" > <!-- "file" submenu --> <menu> <item android:id="@+id/create_new" android:title="@string/create_new" /> <item android:id="@+id/open" android:title="@string/open" /> </menu> </item> </menu>
When the user selects an item from a submenu, the parent menu's respective on-item-selected callback method receives the event. For instance, if the above menu is applied as an Options Menu, then theonOptionsItemSelected()method is called when a submenu item is selected.

• Menu groups

A menu group is a collection of menu items that share certain traits. With a group, you can:

• Show or hide all items withsetGroupVisible()
• Enable or disable all items withsetGroupEnabled()
• Specify whether all items are checkable withsetGroupCheckable()

You can create a group by nesting<item>elements inside a<group>element in your menu resource or by specifying a group ID with the theadd()method.

下面是一個MenuGroups的例子：

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:id="@+id/item1"
          android:icon="@drawable/item1"
          android:title="@string/item1" />
    <!-- menu group -->
    <group android:id="@+id/group1">
        <item android:id="@+id/groupItem1"
              android:title="@string/groupItem1" />
        <item android:id="@+id/groupItem2"
              android:title="@string/groupItem2" />
    </group>
</menu>

• Checkable menu items

You can define the checkable behavior for individual menu items using theandroid:checkableattribute in the<item>element, or for an entire group with theandroid:checkableBehaviorattribute in the<group>element. For example, all items in this menu group are checkable with a radio button:

<?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <group android:checkableBehavior="single"> <item android:id="@+id/red" android:title="@string/red" /> <item android:id="@+id/blue" android:title="@string/blue" /> </group> </menu>
哎，今天先寫到這了，有機會下次再介紹，謝謝！