Question

我目前正在开发一个从外部存储中读取的动态壁纸。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。我似乎无法测试这个，因为外部存储似乎立即挂载在我的设备上，我不知道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，系统是否真正实现了BOOT_COMPLETED意图。

如果没有，等待外部存储准备就绪的正确方法是什么。我想在应用程序的开头调用类似的东西

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，以防它进入MEDIA_REMOVED - ＆gt; MEDIA_UNMOUNTED - ＆gt; MEDIA_CHECKING（可选） - ＆gt; MEDIA_READY开机了吗？

Answer 1

您可以注册BroadcastReceiver以收听外部存储状态的更改：

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

在updateExternalStorageState()中，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
    }
}

Answer 2

使用广播接收器，侦听Intent.ACTION_MEDIA_MOUNTED：广播操作：外部媒体存在并安装在其挂载点。

Answer 3

我非常需要。我正在从SD卡读取配置文件，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 OS自动安装SD卡。如果没有，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");
}

Android - 等待外部存储准备就绪

3 个答案: