如何将 BackgroundWorker 的结果设置为 TextView

Question

我对 android 非常陌生，无法将数据库中的结果输入屏幕上的TextView。目前，我的应用程序在单击按钮后返回一条消息。我在屏幕上有两个TextView 元素txtViewBegin 和txtViewEind。从mySql（通过php）我得到一个像22-02-2014 24-05-2017 这样的字符串，我将其拆分为Strings (.split(" ")) 的数组。

我可以使用后台工作人员的setTextView（onPostExecute 吗？）

或者我应该在我的MainActivity 中这样做吗？在这方面仍然是菜鸟。对不起。

这是我的BackgroundWorker：

public class BackgroundWorker extends AsyncTask<String,Void,String> {
Context context;
AlertDialog alertDialog;
BackgroundWorker(Context ctx){
    context = ctx;
}


@Override
protected String doInBackground(String... params) {
    String type = params[0];
    String login_url= "http://*************/****.php";
    if(type.equals("Draai")){
        try {
            URL url = new URL(login_url);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(false);
            httpURLConnection.setDoInput(true);
            //OutputStream outputStream = httpURLConnection.getOutputStream();
            //BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
            //String post_data = URLEncoder.encode("user_name""UTF-8")// HIER KUN JE VARIABELEN INGEVEN DIE WORDEN GEIMPLEMENTEERD IN HET PHP DOCUMENT
            //bufferedWriter.write();
            //bufferedWriter.flush();
            // bufferedWriter.close();
            //outputStream.close();
            InputStream inputStream = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(inputStream, "iso-8859-1"));
            String result ="";
            String line="";
            while ((line=bufferedReader.readLine()) != null){
                result += line;
            }
            String[] separated = result.split(" ");
            bufferedReader.close();
            inputStream.close();
            httpURLConnection.disconnect();
            return result;

        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (Exception e){
            e.printStackTrace();
        }
    }
    return null;
}

@Override
protected void onPreExecute() {
        alertDialog = new AlertDialog.Builder(context).create();
        alertDialog.setTitle("TijdsDuur");
}

@Override
protected void onPostExecute(String result) {
    alertDialog.setMessage(result);
    alertDialog.show();
}

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

还有我的MainActivity:

public class MainActivity extends AppCompatActivity {
TextView ViewBegin, ViewEind;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    ViewBegin = (TextView) findViewById(R.id.txtViewBegin);
    ViewEind = (TextView) findViewById(R.id.txtViewEind);
}

public void onDraai(View view){
    String type = "Draai";

    BackgroundWorker backgroundWorker = new BackgroundWorker(this);
    backgroundWorker.execute(type);

}
}

Answer 1

1.) 在您的BackgroundWorker 中为回调创建一个interface

public interface DataCallBack{
     void onDataReceived(String s);
}

2.) 在 Activity 中实现该回调接口

public class MainActivity extends AppCompatActivity implements BackgroundWorker.DataCallBack {

3.) 任务完成后，通知您的活动并显示数据

你的MainActivity 看起来像

public class MainActivity extends AppCompatActivity implements BackgroundWorker.DataCallBack {
TextView ViewBegin, ViewEind;

  // .....code

    @Override
    void onDataReceived(String s){
         if(s!=null){
            String[] separated = result.split(" ");
            ViewBegin.setText(separated[0]);  
            ViewEind.setText(separated[1]);  
         }    
    }

  // .....code

}

你的 BackgroundWorker 类看起来像

public class BackgroundWorker extends AsyncTask<String,Void,String> {
    Context context;
    AlertDialog alertDialog;
    DataCallBack callback;

    BackgroundWorker(Context ctx){
        context = ctx;

        // initialize the callback reference
        callback = (DataCallBack) cxt;
    }

    public interface DataCallBack{
         void onDataReceived(String s);
    }

    // .....code

    @Override
    protected void onPostExecute(String result) {
        callback.onDataReceived(result);
        // ^^^ send data to Activity

        alertDialog.setMessage(result);
        alertDialog.show();
    }

    // .....code

}