java - 使用 doInBackground 的结果设置 textView

Question

我是 Android 新手，我尝试使用 php 脚本与本地主机进行通信并访问一个简单的数据库。我在 doInBackground() 方法中定义了一个任务，该任务从存储在本地主机上的数据库中获取值(我不知道该部分是否有效)。我想使用 doInBackground 方法返回的结果在 Activity 的 TextView 中设置文本。

public class BackgroundWorker extends AsyncTask<String,Void,String> {

    Context context;


    BackgroundWorker(Context ctx)
    {
        context = ctx;
    }

    @Override
    protected String doInBackground(String... params) {
        String group = params[0];
        String child = params[1];
        String address = "http://10.0.2.2/conn.php";

        URL url = null;
        try {
            url = new URL(address);
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            httpURLConnection.setRequestMethod("POST");
            httpURLConnection.setDoOutput(true);
            httpURLConnection.setDoInput(true);
            OutputStream outputStream = httpURLConnection.getOutputStream();
            BufferedWriter bufferedWriter = new BufferedWriter(new OutputStreamWriter(outputStream, "UTF-8"));
            String post_data = URLEncoder.encode("group", "UTF-8") + "=" + URLEncoder.encode(group, "UTF-8") + "&"
                    + URLEncoder.encode("child", "UTF-8") + "=" + URLEncoder.encode(child, "UTF-8");
            bufferedWriter.write(post_data);
            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;
            }
            bufferedReader.close();
            inputStream.close();
            httpURLConnection.disconnect();
            return result;
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

    }


    @Override
    protected void onPreExecute() {
        super.onPreExecute();
    }

    @Override
    protected void onPostExecute(String s) {

        super.onPostExecute(s);
    }

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

以及 Activity 类:

public class viewTT extends Activity {
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_view_tt);


        Button btnNextScreen = (Button) findViewById(R.id.button);
        TextView txtName = (TextView) findViewById(R.id.textView);
        TextView txtName2 = (TextView) findViewById(R.id.textView2);

        Intent i = getIntent();
        // Receiving the Data
        String group= i.getStringExtra("group");
        String child = i.getStringExtra("child");
        txtName.setText(group+" "+child);

        BackgroundWorker backgroundWorker = new BackgroundWorker(this);
         backgroundWorker.execute(group,child);



        btnNextScreen.setOnClickListener(new View.OnClickListener() {

                    public void onClick(View arg0)
                    {
                //Starting a new Intent
                          Intent nextScreen = new Intent(getApplicationContext(), MainActivity.class);
                            startActivity(nextScreen);
                    }
         });
    }
}

我想设置txtName2。

Answer 1

您可以使用接口(interface)将数据返回到您的 Activity

界面

    public interface AsyncResponse {
    public void onFinish(Object output);
}

SomeAsyncTask 类

public class SomeAsyncTask extends AsyncTask<String, String, String> {
private AsyncResponse asyncResponse;

public SomeAsyncTask(AsyncResponse asyncResponse) {
    this.asyncResponse = asyncResponse;

}

@Override
protected String doInBackground(String... params) {

   //Do something 
    .....
   //Finally return something

   return "returnSomeString";
}

@Override
protected void onPostExecute(String s) {
    super.onPostExecute(s);
    asyncResponse.onFinish(s);
}}

在要设置 View 的 Activity 中，像这样调用 SomeAsyncTask 类

    SomeAsyncTask someAsyncTask=new SomeAsyncTask(new AsyncResponse() {
        @Override
        public void onFinish(Object output) {
            String result= (String) output;
            //Finally set your views
        }
    });
    someAsyncTask.execute();
}