Java 如何在 Asynctask 中获取共享首选项？
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How do I get sharedpreferences in Asynctask?
提问by user3316779
I am writing an android application for my school project but i am stuck here. The problem is i have to access a SharedPreferencesvalue and need it in an AsyncTaskclass. When I try to access it, it wont let me because of the context. How can i reach my SharedPreferencesin my AsyncTask?
我正在为我的学校项目编写一个 android 应用程序，但我被困在这里。问题是我必须访问一个SharedPreferences值并在AsyncTask类中需要它。当我尝试访问它时，它不会让我因为上下文。我怎样才能达到我SharedPreferences的AsyncTask？
public class CheckAccess extends AsyncTask<JSONObject, Integer, Boolean>{
@Override
protected Boolean doInBackground(JSONObject... params) {
//Trying to get sharedpreferences here wont work.
return null;
}
}
采纳答案by Green goblin
Override onPreExecuteor onPostExecutemethod of AsyncTaskand get SharedPreferencesthere:
覆盖onPreExecute或onPostExecute方法AsyncTask并到达SharedPreferences那里：
@Override
protected void onPreExecute() {
super.onPreExecute();
//get sharedPreferences here
SharedPreferences sharedPreferences = getSharedPreferences(<SharedPreferencesName>, <Mode>);
}
Please note that getSharedPreferencesis an Activitymethod. So, you need to call it through Contextif you are not using it in Activity.
请注意，这getSharedPreferences是一种Activity方法。因此，Context如果您不在Activity.
回答by tlahoda
You can get SharedPreferences in a background thread using the PreferenceManager like this:
您可以使用 PreferenceManager 在后台线程中获取 SharedPreferences，如下所示：
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(<YourActivity>.this);
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(<YourActivity>.this);
回答by Richard Le Mesurier
You can get SharedPreferencesin the background using an AsyncTask.
您可以SharedPreferences使用AsyncTask.
The mistake is in this line, where you are passing in the wrong type of variable:
错误在于这一行，您传入了错误类型的变量：
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
In your case, the word thisrefers to the AsyncTaskinstance that you are calling if from.
在您的情况下，该词this指的AsyncTask是您正在调用的实例。
What I do is I pass the Contextin to the task in the execute()method. See the code below for a working example:
我所做的是将Contextin传递给方法中的任务execute()。有关工作示例，请参阅下面的代码：
new AsyncTask<Context, Void, String>()
{
@Override
protected String doInBackground(Context... params)
{
Context context = params[0];
SharedPreferences prefs =
context.getSharedPreferences("name of shared preferences file",
Context.MODE_PRIVATE);
String myBackgroundPreference = prefs.getString("preference name", "default value");
return myBackgroundPreference;
}
protected void onPostExecute(String result)
{
Log.d("mobiRic", "Preference received in background: " + result);
};
}.execute(this);
In the above example, thisrefers to the Activityor Servicethat I call this from.
在上面的例子中，this指的是我称之为的Activity或Service。
