Fetch data in background and display in UI

问题

I'm using volley to fetch data using volley and display in User Interface, and it takes time to load the data. What i want to happen is, I want to fetch the data in background during the splash screen or loading screen and display it in User interface. I want the fetching part to be done in another activity and it should be a background service and this should be called in "main activity" to populate the fields.

回答1:

You can try using the AsyncTask. So the process goes like that:

In onPreExecute() you can show a ProgresDialog or a ProgresBar to visualize your loading process
in doInBackground(Params...) you start loading your data
and in onPostExecute(Result) you display your data in UI and hide your ProgresDialog/ProgresBar.

Example of AsyncTask usage.

Do it like this:

private class LoadDataBaseData extends AsyncTask<String, Void, String> {

    @Override
    protected String doInBackground(String... params) {
        //Start loading your data 

        return "Data loaded";
    }

    @Override
    protected void onPostExecute(String result) {
       //Update your UI with data you loaded/start your activity with loaded data

    }

    @Override
    protected void onPreExecute(){     
    }

    @Override
    protected void onProgressUpdate(Void... values) {
    }
}

回答2:

use AsyncTask like that

 private class LongOperation extends AsyncTask<String, Void, String>
   {

    @Override
    protected String doInBackground(String... params)
    {
       //do your work here 


        return "Executed";
    }

    @Override
    protected void onPostExecute(String result)
    {
        progressBar.dismiss();

    }

    @Override
    protected void onPreExecute()
    {
        progressBar = ProgressDialog.show(getActivity(), null, "message...");
        progressBar.show();
    }

    @Override
    protected void onProgressUpdate(Void... values)
    {
    }
}

来源：https://stackoverflow.com/questions/51647605/fetch-data-in-background-and-display-in-ui

标签

android

json

android-volley