从AsyncTask更新视图

Question

我想在android中从mysql数据库中检索数据，并在textview中显示

这是后台asynctask代码

public class BackgroundAsyncTask extends AsyncTask<String, Void, String> {
Context ctx;
TextView tv;

BackgroundAsyncTask(Context ctx) {
    this.ctx = ctx;
}
protected void onPreExecute() {
    super.onPreExecute();
}

@Override
protected String doInBackground(String... params) {
    String insert_url="http://192.168.10.3:81/android_exam_practice/insert.php";
    String select_url="http://192.168.10.3:81/android_exam_practice/select.php";
    String method=params[0];
    if(method.equals("insert"))
    {
        String name=params[1];
        String email=params[2];
        try {
            URL url=new URL(insert_url);
            HttpURLConnection httpURLConnection=(HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            OutputStream outputStream=httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter=new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
            String data= URLEncoder.encode("name","UTF-8")+"="+URLEncoder.encode(name,"UTF-8")+"&"+
                    URLEncoder.encode("email","UTF-8")+"="+URLEncoder.encode(email,"UTF-8");
            bufferedWriter.write(data);
            bufferedWriter.flush();
            outputStream.close();
            InputStream inputStream=httpURLConnection.getInputStream();
            inputStream.close();
            return "data inserted ";
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
    else if(method.equals("select"))
    {
 //   String Name=params[1];
   // String Email=params[2];
        try {
            URL url=new URL(select_url);
            HttpURLConnection httpURLConnection=(HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("post");
            httpURLConnection.setDoInput(true);
            httpURLConnection.setDoOutput(true);
            //OutputStream outputStream=httpURLConnection.getOutputStream();
            //BufferedWriter bufferedWriter=new BufferedWriter(new OutputStreamWriter(outputStream,"UTF-8"));
            //String data =URLEncoder.encode("");
            InputStream inputStream=httpURLConnection.getInputStream();
            BufferedReader bufferedReader=new BufferedReader(new InputStreamReader(inputStream,"iso-8859-1"));
            String response ="";
            String line ="";
            while((line=bufferedReader.readLine())!=null)
            {
                response+=line;
            }
            bufferedReader.close();
            inputStream.close();
            httpURLConnection.disconnect();
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    return null;
}

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

@Override
protected void onPostExecute(String aVoid) {
    super.onPostExecute(aVoid);
   // Toast.makeText(ctx, aVoid, Toast.LENGTH_SHORT).show();
    tv.setText(aVoid);
}

}

Answer 1

你的解决方案在这里。

在OnPostExecute()方法中初始化TextView

@Override
protected void onPostExecute(String aVoid) {
    super.onPostExecute(aVoid);
   // Toast.makeText(ctx, aVoid, Toast.LENGTH_SHORT).show();
    tv = findViewById(R.id.textView); 
    tv.setText(aVoid);
}