【Android】Android 移動應用資料到SD

【Android】Android 移動應用資料到SD

在應用的menifest檔案中指定就可以了，在 <manifest> 元素中包含android:installLocation 屬性，設定其值為"internalOnly"即可，如下：

<manifest xmlns:android="http://schemas.android.com/apk/res/android"  android:installLocation="internalOnly"  ... >  

android:installLocation 還有另外兩個屬性值："preferExternal"和"auto"，根據字面意思大概也能明白是什麼意思了，還是說明如下：

如果你定義了 "preferExternal"，意味着你要求你的應用安裝至擴充存儲，但是系統不能保證應用肯定會安裝至擴充存儲。如果擴充存儲沒有空間了，系統将把應用安裝到内置存儲。使用者可以在兩個位置之間移動你的應用。 

如果你定義了 "auto"，表示你的應用可能會安裝在擴充存儲，但是對安裝位置沒有特别的偏好。系統将基于很多因素決定你的應用安裝到哪裡。使用者同樣可以将應用在兩個位置之間移動

我們在使用Android手機時發現，有的程式允許被移動到SD卡，而有的不行？這是為什麼呢？

因為在Android 2.2版之後， Android應用才被允許移動到SD卡中。而在此之前開發的應用，全部沒有這個功能。

那麼究竟如何允許你的應用移動到SD卡呢？答案其實很簡單，隻要給Manifest設定一個installLocation屬性即可。

這個屬性設定的是預設安裝位置， 共有三個有效值，auto、internalOnly、preferExternal。

auto 表示自動，由系統決定安裝位置

internalOnly 安裝在手機記憶體

preferExternal 安裝在外部存儲中

看一下修改後的AndroidManifest.xml。

<manifest xmlns:android="http://schemas.android.com/apk/res/android"  
      package="com.yfz"  
      android:installLocation="auto"  
      android:versionCode="1"  
      android:versionName="1.0">      

是不是很簡單？

可能有人會問，如果我的還要支援2.1怎麼辦呢？ 其實不用管啦，你隻要設定  <uses-sdk android:minSdkVersion="7" /> 然後安裝到2.1的裝置上時，Android會忽略這個屬性，直接給你安裝到手機記憶體。

需要額外注意的是，并不是所有程式都适合移到SD卡上。下面就看一下，在哪些條件下，不建議允許程式移動到SD卡上。

Applications That Should NOT Install on External Storage

When the user enables USB mass storage to share files with their computer (or otherwise unmounts or removes the external storage), any application installed on the external storage and currently running is killed. The system effectively becomes unaware of the application until mass storage is disabled and the external storage is remounted on the device. Besides killing the application and making it unavailable to the user, this can break some types of applications in a more serious way. In order for your application to consistently behave as expected, you should not allow your application to be installed on the external storage if it uses any of the following features, due to the cited consequences when the external storage is unmounted:

Services

Your running Service will be killed and will not be restarted when external storage is remounted. You can, however, register for the ACTION_EXTERNAL_APPLICATIONS_AVAILABLE broadcast Intent, which will notify your application when applications installed on external storage have become available to the system again. At which time, you can restart your Service.

Alarm Services

Your alarms registered with AlarmManager will be cancelled. You must manually re-register any alarms when external storage is remounted.

Input Method Engines

Your IME will be replaced by the default IME. When external storage is remounted, the user can open system settings to enable your IME again.

Live Wallpapers

Your running Live Wallpaper will be replaced by the default Live Wallpaper. When external storage is remounted, the user can select your Live Wallpaper again.

Live Folders

Your Live Folder will be removed from the home screen. When external storage is remounted, the user can add your Live Folder to the home screen again.

App Widgets

Your App Widget will be removed from the home screen. When external storage is remounted, your App Widget will not be available for the user to select until the system resets the home application (usually not until a system reboot).

Account Managers

Your accounts created with AccountManager will disappear until external storage is remounted.

Sync Adapters

Your AbstractThreadedSyncAdapter and all its sync functionality will not work until external storage is remounted.

Device Administrators

Your DeviceAdminReceiver and all its admin capabilities will be disabled, which can have unforeseeable consequences for the device functionality, which may persist after external storage is remounted.

Broadcast Receivers listening for "boot completed"

The system delivers the ACTION_BOOT_COMPLETED broadcast before the external storage is mounted to the device. If your application is installed on the external storage, it can never receive this broadcast.

Copy Protection

Your application cannot be installed to a device's SD card if it uses Android Market's Copy Protection feature. However, if you use Android Market's Application Licensing instead, your application can be installed to internal or external storage, including SD cards.

If your application uses any of the features listed above, you should not allow your application to install on external storage. By default, the system will not allow your application to install on the external storage, so you don't need to worry about your existing applications. However, if you're certain that your application should never be installed on the external storage, then you should make this clear by declaring android:installLocation with a value of "internalOnly". Though this does not change the default behavior, it explicitly states that your application should only be installed on the internal storage and serves as a reminder to you and other developers that this decision has been made

上面這段一定要看，很重要。 比如你的程式如果想開機自啟動，那就一定不能允許移動到SD卡了。 因為開機啟動的廣播消息BOOT_COMPLETE在 SD 卡被裝載之前就發出來了，程式根本沒法收到。

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