从另一个线程更新GUI线程

Question

我需要从另一个线程更新GUI线程中的文本区域。我知道我必须使用invokelater。但是不知道如何应用。

这是我尝试更新GUI的地方

MinFrame.logWriter(MinFrame.logGrabber(mf.screen) + "\nDatabase Download Started bhgh",mf.screen);

这是Downloader类的完整代码（辅助线程）

/*
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 * To change this template file, choose Tools | Templates
 * and open the template in the editor.
 */
package jvazrfid;

import java.io.BufferedReader;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.URL;
import java.sql.Statement;
import javax.swing.SwingUtilities;
import org.json.JSONArray;
import org.json.JSONObject;

/**
 *
 * @author tmaxs
 */
public class Downloader implements Runnable {

    public void run() {
        LoginValidator lv = new LoginValidator();
        String updateTime = lv.getupdateDb();

        updateGUI("db", dataDownload(updateTime));

        // Starting Images Download
    }

    public String dataDownload(String updateTime) {
        MinFrame mf = new MinFrame();
        String number = "";
        try {
            String url = "3000/protected/students?updatedAfter=" + updateTime;
            URL obj = new URL(url);
            HttpURLConnection con = (HttpURLConnection) obj.openConnection();
            con.setRequestProperty("Authorization", "BEARER "
                    + "eyJhbGciOiJIUzI1NiIsInR5cCI6IkpXVCJ9.eyJkYXRhIjp7Im5hbWUiOiJJc3VydSBSdWh1bmFnZSIsInMTU1ODkzOTI0NiwiZXhwIjoxNTU4OTQ2NDQ2fQ.1Vi0TNPWUNgE2e-OXNfQj92_bfOXkfEBjtymW1qGiDY");
            int responseCode = con.getResponseCode();
            System.out.println("\nSending 'GET' request to URL : " + url);
            System.out.println("Response Code : " + responseCode);
            BufferedReader in = new BufferedReader(
                    new InputStreamReader(con.getInputStream()));
            String inputLine;
            StringBuffer response = new StringBuffer();
            while ((inputLine = in.readLine()) != null) {
                response.append(inputLine);
            }
            in.close();
            //print in String

            // JSONObject objt = new JSONObject(response);
            JSONArray array = new JSONArray(response.toString());

            DownloadImage image = new DownloadImage();
            System.out.println("Text : " + MinFrame.logGrabber(mf.screen));
            MinFrame.logWriter(MinFrame.logGrabber(mf.screen) + "\nDatabase Download Started bhgh",mf.screen);
           // SwingUtilities.invokeLater(mf.screen);
            System.out.println("Database Download Started hhh");
            for (int i = 0; i < array.length(); i++) {
                JSONObject object = array.getJSONObject(i);
                String ImageStatus = image.ImageDownloader(object.getString("indexNo"));
                try {

                    Statement s = DBL.getConnection().createStatement();
                    s.executeUpdate("INSERT INTO `students` (`active`, "
                            + "`verified`, "
                            + "`_id`, "
                            + "`indexNo`, "
                            + "`initials`, "
                            + "`lastName`, "
                            + "`fullName`, "
                            + "`DOB`, "
                            + "`gender`, "
                            + "`address`, "
                            + "`grade`, "
                            + "`section`, "
                            + "`medium`, "
                            + "`homeTel`, "
                            + "`imageDownloaded`) VALUES "
                            + "('" + object.getBoolean("active") + "',"
                            + "'" + object.getBoolean("verified") + "', "
                            + "'" + object.getString("_id") + "', "
                            + "'" + object.getString("indexNo") + "', "
                            + "'" + object.getString("initials") + "', "
                            + "'" + object.getString("lastName") + "', "
                            + "'" + object.getString("fullName") + "', "
                            + "'" + object.getString("DOB") + "', "
                            + "'" + object.getString("gender") + "', "
                            + "'" + object.getString("address") + "', "
                            + "'" + object.getString("grade") + "', "
                            + "'" + object.getString("section") + "', "
                            + "'" + object.getString("medium") + "', "
                            + "'" + object.getString("homeTel") + "', "
                            + "'" + ImageStatus + "')");

                    Statement updateDate = DBL.getConnection().createStatement();
                    updateDate.executeUpdate("update updates set timestamp = '" + object.getString("updatedAt") + "' where id = 1");
                    number = Integer.toString(i);
                    DBL.getConnection().close();

                } catch (Exception ex) {

                    ex.printStackTrace();
                    mf.logWriter(mf.logGrabber(mf.screen) + "\nDatabase error",mf.screen);
                    return "Database error";

                }
                mf.logWriter(mf.logGrabber(mf.screen) + "\nDatabase Download finished",mf.screen);
                System.out.println("Database Download finished");
            }
  MinFrame.logWriter(MinFrame.logGrabber(mf.screen) + "\nNo values Retrieved",mf.screen);

            /*System.out.println("base -" + myresponse.getString("base"));
   System.out.println("date -" + myresponse.getString("date"));
   JSONObject rates_object = new JSONObject(myresponse.getJSONObject("rates").toString());
   System.out.println("rates -" + rates_object);
   System.out.println("AUD -" + rates_object.getDouble("AUD"));
   System.out.println("BGN -" + rates_object.getDouble("BGN"));
   System.out.println("BRL -" + rates_object.getDouble("BRL"));
    System.out.println("CAD -" + rates_object.getDouble("CAD"));*/
        } catch (Exception e) {
            System.out.println(e);
            return "URL Parse Error";

        }
        return number;
    }


    private void updateGUI(String key, String val) {
        if (key.equalsIgnoreCase("db")) {
            System.out.println("here");
            SpalshScreen screen = new SpalshScreen();
            screen.databaseDownload.setText("Database Download successful - " + val + " rows downloaded");
        }

    }
}