android.intent.action.EXTERNAL_APPLICATIONS_UNAVAILABLE

String android.content.Intent.ACTION_EXTERNAL_APPLICATIONS_UNAVAILABLE = "android.intent.action.EXTERNAL_APPLICATIONS_UNAVAILABLE"

Broadcast Action: Resources for a set of packages are currently unavailable since the media on which they exist is unavailable. The extra data EXTRA_CHANGED_PACKAGE_LIST contains a list of packages whose availability changed. The extra data EXTRA_CHANGED_UID_LIST contains a list of uids of packages whose availability changed. The specified set of packages can no longer be launched and are practically unavailable on the system.

Inclues the following extras:

    * EXTRA_CHANGED_PACKAGE_LIST is the set of packages whose resources are no longer available. EXTRA_CHANGED_UID_LIST is the set of packages whose resources are no longer available.

This is a protected intent that can only be sent by the system.

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这个action从2.2版本才开始支持。

当SD卡从可用变为不可用且系统中有部门应用之前安装在SD卡上时，
则会发出这个广播，此时，这些之前安装在SD卡中的应用不存在系统中了。

这个广播的intent中包括如下数据：
1.变为不可用的应用包名列表
2.变为不可用的应用ID列表

这种广播只能由系统发出。