Android文檔Training之ActionBar

ActionBar 是Activity中最重要的設計元素之一，在你的app中添加ActionBar的方法如下

只兼容Android 3.0 及以上（SDK>=11）

1. Activity主題必須爲Theme.Holo一類的主題

  <activity
        android:name=".HomeActivity"
        android:theme="@android:style/Theme.Holo"/>

2. 給ActionBar添加Action

<menu xmlns:android="http://schemas.android.com/apk/res/android" >
    <!-- Search, should appear as action button -->
    <item android:id="@+id/action_search"
          android:icon="@drawable/ic_action_search"
          android:title="@string/action_search"
          android:showAsAction="ifRoom" />
    <!-- Settings, should always be in the overflow -->
    <item android:id="@+id/action_settings"
          android:title="@string/action_settings"
          android:showAsAction="never" />
</menu>

添加菜單

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu items for use in the action bar
    MenuInflater inflater = getMenuInflater();
    inflater.inflate(R.menu.main_activity_actions, menu);
    return super.onCreateOptionsMenu(menu);
}

添加點擊事件

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle presses on the action bar items
    switch (item.getItemId()) {
        case R.id.action_search:
            openSearch();
            return true;
        case R.id.action_settings:
            openSettings();
            return true;
        default:
            return super.onOptionsItemSelected(item);
    }
}

兼容Android 2.1 及以上（SDK>=7）

1. 添加支持庫

 compile 'com.android.support:appcompat-v7:25.1.0'

2. 設置Activity集成ActionBarActivity或者設置主題爲Theme.AppCompat一類的主題，即下面二選一

public class MainActivity extends ActionBarActivity {

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

或者

<activity android:name=".MainActivity"
android:theme="@style/Theme.AppCompat.Light.DarkActionBar"/>

3. 給ActionBar添加Action

<menu xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:yourapp="http://schemas.android.com/apk/res-auto">
    <!-- Search, should appear as action button -->
    <item android:id="@+id/action_search"
        android:icon="@mipmap/ic_launcher"
        android:title="@string/app_name"
        yourapp:showAsAction="ifRoom" />
    <!-- Settings, should always be in the overflow -->
    <item android:id="@+id/action_settings"
        android:title="@string/app_name"
        yourapp:showAsAction="never" />
</menu>

4. 剩下步驟與上面一樣

給ActionBar添加默認的返回上一頁action

<application ... >
    ...
    <!-- The main/home activity (it has no parent activity) -->
    <activity
        android:name="com.example.myfirstapp.MainActivity" ...>
        ...
    </activity>
    <!-- A child of the main activity -->
    <activity
        android:name="com.example.myfirstapp.DisplayMessageActivity"
        android:label="@string/title_activity_display_message"
        android:parentActivityName="com.example.myfirstapp.MainActivity" >
        <!-- Parent activity meta-data to support 4.0 and lower -->
        <meta-data
            android:name="android.support.PARENT_ACTIVITY"
            android:value="com.example.myfirstapp.MainActivity" />
    </activity>
</application>

使按鈕有效

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_displaymessage);
    getSupportActionBar().setDisplayHomeAsUpEnabled(true);
    // If your minSdkVersion is 11 or higher, instead use:
    // getActionBar().setDisplayHomeAsUpEnabled(true);
}

自定義ActionBar樣式（android3.0及以上）

使用系統樣式

<application android:theme="@android:style/Theme.Holo.Light" ... />

自定義樣式

在style.xml中定義並在manifest中使用

 <!-- the theme applied to the application or activity -->
    <style name="CustomActionBarTheme"
           parent="@style/Theme.Holo">
        <item name="android:actionBarStyle">@style/MyActionBar</item>
        <item name="android:actionBarTabTextStyle">@style/MyActionBarTabText</item>
        <item name="android:actionMenuTextColor">@color/actionbar_text</item>
    </style>

    <!-- ActionBar styles -->
    <style name="MyActionBar"
           parent="@style/Widget.Holo.ActionBar">
        <item name="android:titleTextStyle">@style/MyActionBarTitleText</item>
    </style>

    <!-- ActionBar title text -->
    <style name="MyActionBarTitleText"
           parent="@style/TextAppearance.Holo.Widget.ActionBar.Title">
        <item name="android:textColor">@color/actionbar_text</item>
    </style>

    <!-- ActionBar tabs text styles -->
    <style name="MyActionBarTabText"
           parent="@style/Widget.Holo.ActionBar.TabText">
        <item name="android:textColor">@color/actionbar_text</item>
    </style>

使用如下

<application android:theme="@style/CustomActionBarTheme" ... />

自定義ActionBar樣式（android2.1及以上）與上面基本一樣，不同點是基本Theme的設置，例如

<!-- the theme applied to the application or activity -->
    <style name="CustomActionBarTheme"
           parent="@style/Theme.AppCompat">
        <item name="android:actionBarStyle">@style/MyActionBar</item>
        <item name="android:actionBarTabTextStyle">@style/MyActionBarTabText</item>
        <item name="android:actionMenuTextColor">@color/actionbar_text</item>

        <!-- Support library compatibility -->
        <item name="actionBarStyle">@style/MyActionBar</item>
        <item name="actionBarTabTextStyle">@style/MyActionBarTabText</item>
        <item name="actionMenuTextColor">@color/actionbar_text</item>
    </style>

    <!-- ActionBar styles -->
    <style name="MyActionBar"
           parent="@style/Widget.AppCompat.ActionBar">
        <item name="android:titleTextStyle">@style/MyActionBarTitleText</item>

        <!-- Support library compatibility -->
        <item name="titleTextStyle">@style/MyActionBarTitleText</item>
    </style>

    <!-- ActionBar title text -->
    <style name="MyActionBarTitleText"
           parent="@style/TextAppearance.AppCompat.Widget.ActionBar.Title">
        <item name="android:textColor">@color/actionbar_text</item>
        <!-- The textColor property is backward compatible with the Support Library -->
    </style>

    <!-- ActionBar tabs text -->
    <style name="MyActionBarTabText"
           parent="@style/Widget.AppCompat.ActionBar.TabText">
        <item name="android:textColor">@color/actionbar_text</item>
        <!-- The textColor property is backward compatible with the Support Library -->
    </style>

對ActionBar的簡單使用

     @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //android 3.0 and above
        // ActionBar actionBar = getActionBar();
        //android 2.1 and above
        ActionBar actionBar = getSupportActionBar();
        actionBar.hide();
        //actionBar.show();
    }

開啓ActionBar覆蓋模式

當actionbar在hide或show時會引起佈局重繪浪資源，所以引進overlay mode使得actionbar一直在整個頁面的最上方（設置actionbar背景半透明） 不佔據屏幕位置

android3.0及以上

<!-- the theme applied to the application or activity -->
<style name="CustomActionBarTheme"
       parent="@android:style/Theme.Holo">
    <item name="android:windowActionBarOverlay">true</item>
</style>

android2.1及以上

<!-- the theme applied to the application or activity -->
<style name="CustomActionBarTheme"
       parent="@android:style/Theme.AppCompat">
    <item name="android:windowActionBarOverlay">true</item>

    <!-- Support library compatibility -->
    <item name="windowActionBarOverlay">true</item>
</style>

當設置覆蓋模式後，會使得部分應該顯示爲visible的佈局在actionbar下面顯示很模糊，爲了確保這部分完全可視，我們可以給這部分佈局的頂部設置margin或padding，屬性值設置爲actionBarSize,如下（android3.0及以上）

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?android:attr/actionBarSize">
    ...
</RelativeLayout>

當設置爲android2.1及以上可用時，改爲

<!-- Support library compatibility -->
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingTop="?attr/actionBarSize">
    ...
</RelativeLayout>