5

我目前正在开发一种从外部存储读取的动态壁纸。当设备启动时，我认为可以在存储准备好之前启动动态壁纸。特别是如果它进行定期错误检查。其他人正在报告问题，我认为这就是原因。我似乎无法对此进行测试，因为外部存储似乎会立即安装在我的设备上，而且我不确定如何强制它进行错误检查。所以我的第一个问题是，在启动动态壁纸之前，系统是否真的按照 BOOT_COMPLETED 意图进行操作。

如果没有，等待外部存储准备就绪的正确方法是什么。我正在考虑在应用程序的开头调用这样的东西

public void waitForExternalStorage()
{
    while(Environment.getExternalStorageState().equals(Environment.MEDIA_CHECKING))
    {
        try { Thread.sleep(1000L); }
        catch(InterruptedException e) { e.printStackTrace(); }
    }
}

我是否必须检查其他情况，以防它在启动时进入 MEDIA_REMOVED -> MEDIA_UNMOUNTED -> MEDIA_CHECKING(optional) -> MEDIA_READY？

4

3 回答 3

8

你可以注册一个BroadcastReceiver来监听外部存储状态的变化：

BroadcastReceiver externalStorageStateReceiver = new BroadcastReceiver() {
    @Override
    public void onReceive(Context context, Intent intent) {
        updateExternalStorageState();
    }
};

IntentFilter filter = new IntentFilter();
filter.addAction(Intent.ACTION_MEDIA_MOUNTED);
filter.addAction(Intent.ACTION_MEDIA_REMOVED);
registerReceiver(mExternalStorageReceiver, filter);
updateExternalStorageState(); // You can initialize the state here, before any change happens

并且updateExternalStorageState()您可以检查更改后的实际状态：

protected void updateExternalStorageState() {
    String state = Environment.getExternalStorageState();
    if (Environment.MEDIA_MOUNTED.equals(state)) {
        // SD card is mounted and ready for use
    } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
        // SD card is mounted, but it is read only
    } else {
        // SD card is unavailable
    }
}
于 2012-10-05T15:04:25.220 回答
3

使用广播接收器，监听Intent.ACTION_MEDIA_MOUNTED：广播动作：外部媒体存在并安装在其安装点。

于 2012-10-05T15:02:30.370 回答
1

我正是需要那个。我正在从 SD 卡中读取配置文件，而我的启动运行应用程序根本无法在不读取它的情况下运行。一个简单的解决方案是等待最多 15-30 秒，以便 Android 操作系统自动挂载 SD 卡。如果不是，则抛出异常。这是代码。只需增加最大计数限制即可增加等待时间。ExternalStorageNotReadyException 是一个自定义异常。

public void awaitExternalStorageInitialization()
        throws ExternalStorageNotReadyException {
    boolean mExternalStorageAvailable = false;
    boolean mExternalStorageWriteable = false;
    int count = 0;

    do {
        String state = Environment.getExternalStorageState();
        if(count > 0) {
            try {
                Thread.sleep(3000);
            } catch (InterruptedException e) {
                Log.e(Constants.LOG_TAG, e.getMessage(), e);
            }
        }
        if (Environment.MEDIA_MOUNTED.equals(state)) {
            // We can read and write the media
            mExternalStorageAvailable = mExternalStorageWriteable = true;
        } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
            // We can only read the media
            mExternalStorageAvailable = true;
            mExternalStorageWriteable = false;
        } else {
            // Something else is wrong. It may be one of many other states,
            // but all we need
            // to know is we can neither read nor write
            mExternalStorageAvailable = mExternalStorageWriteable = false;
        }
        count++;
    } while ((!mExternalStorageAvailable) && (!mExternalStorageWriteable) && (count < 5));
    if(!mExternalStorageWriteable)
        throw new ExternalStorageNotReadyException("External storage device (SD Card) not yet ready");
}
于 2013-07-16T22:05:30.887 回答