等待JSON响应完成，然后再更新字段

Question

Currently in my application I execute a JSONDownloader, then tell my application to wait for a set period of time before updating fields with the retrieved data. How do I go about making the application wait for the JSONDownloader to finish its' task before I update the fields?

The JSONDowloader class is written (abridged) as follows and is run as an asynchronous activity. This class is called when needed and sets global variables which, after a set amount of time after being called are updated. I'd like the fields to be updated as soon as the class has finished running.

public class JSONDownloader extends AsyncTask<Object, Object, Object>{

    @Override
    protected Object doInBackground(Object... params) {
        if(JSONstate == false){
            try {
                final URL url = new URL("https://irrelevant");

                final URLConnection urlConnection = url.openConnection();
                urlConnection.setRequestProperty("Content-Type", "application/json; charset=utf-8");
                urlConnection.connect();
                final InputStream inputStream = urlConnection.getInputStream();
                final StringBuilder sb = new StringBuilder();
                while (inputStream.available() > 0) {
                    sb.append((char) inputStream.read());
                }
                System.out.println("up to setting string");
                String result = sb.toString();

                JSONObject jsonOrg = new JSONObject(result);

                String ok = "ok";

                Response = jsonOrg.getString("response");
                System.out.println(Response);

                if(Response.equals(ok)){
                    Settingsresponse = true;

                    orgName = jsonOrg.getString("orgName");
                    System.out.println("orgName" + orgName);
                    accessPointName = jsonOrg.getString("accessPointName");
                    System.out.println("accessPointName" + accessPointName);
                    lat = jsonOrg.getString("latitude");
                    System.out.println("lat" + lat);
                    longi = jsonOrg.getString("longitude");
                    System.out.println("longi" + longi);
                    floor = jsonOrg.getString("floor");
                    System.out.println("floor" + floor);
                    orgId = jsonOrg.getString("orgId");
                    System.out.println("orgId" + orgId);
                }
                else{
                    System.out.println("Data sent was erroneous");
                    Settingsresponse = false;
                }

            } catch (Exception e) {
                System.err.print(e);      
            }
        }
        return null;
    }
    protected void onPostExecute(Void result){
    }
}

The JSONDownloader is called within whatever method it is needed and then immediately after this is called; currently a set time is used before updating fields as thus:

public void waitthencall()
{
    long t0,t1;
    t0=System.currentTimeMillis();
    do{
        t1=System.currentTimeMillis();
    }
    while (t1-t0<2000);

    setfields();
}

Answer 1

you need a Callback listener to update your UI. Example

Create a callback listener and implement it inside your activity or from where you are updating the UI.

Answer 2

By using asynchronous task!

http://www.vogella.com/articles/AndroidBackgroundProcessing/article.html

May help!

Answer 3

杜德（Dude），一旦doInBackGround完成处理之后，就会调用onPostExecute方法，它将向您保证doInBackGround已完成执行