AsyncTask_初级应用

package com.example.day3;

import android.graphics.Bitmap;
import android.os.AsyncTask;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.widget.TextView;

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.net.HttpURLConnection;
import java.net.MalformedURLException;
import java.net.URL;
import java.net.URLConnection;

public class AsyncTaskActivity extends AppCompatActivity {

private TextView info;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_async_task);

	
    info = findViewById(R.id.info);
    //
    //子线程处理数据   主线程处理ui
    //Thread + Handler
    //AsyncTask   -> 线程池(2)
    requestData();
}

private String apiUrl = "https://tcc.taobao.com/cc/json/mobile_tel_segment.htm?tel=18679906337";

private void requestData() {
    //创建AcyncTask，实现doInBackground方法
    //调execute执行 -> 会导致doInBackground执行
    //doInBackground执行完成，返回结果  -> 会导致onPostExecute执行
    //execute()  ->   doInBackground()子线程中  ->  onPostExecute()主线程中
    //三个泛型
    //Params   执行doInBackground的方法参数类型，调用execute()时传递过去
    //Progress
    //Result  执行doInBackground的返回类型
    new AsyncTask<String, Void, String>() {//void
        //实现doInBackground方法
        @Override
        protected String doInBackground(String[] objects) {//在子线程(后台)执行
            String result = "";

            try {
                URL url = new URL(objects[0]);
                HttpURLConnection urlConnection = (HttpURLConnection) url.openConnection();
                urlConnection.setRequestMethod("GET");
                urlConnection.setConnectTimeout(5000);
                urlConnection.setReadTimeout(5000);
                int responseCode = urlConnection.getResponseCode();
                if(responseCode == 200) {
                    result = stream2String(urlConnection.getInputStream(), "gbk");
                }
            } catch (MalformedURLException e) {
                e.printStackTrace();
            } catch (IOException e) {
                e.printStackTrace();
            }

            return result;
        }

        //当后台处理完成返回执行    在主线程中回调
        @Override
        protected void onPostExecute(String s) {
            info.setText(s);
        }
    }.execute(apiUrl);
}

private String stream2String(InputStream inputStream, String charsetName) throws IOException {
    StringBuilder stringBuilder = new StringBuilder();

    InputStreamReader isr = new InputStreamReader(inputStream, charsetName);

    BufferedReader br = new BufferedReader(isr);

    //读取一行
    //一行文本   null
    for (String tmp = br.readLine(); tmp != null; tmp = br.readLine()) {
        stringBuilder.append(tmp);
    }

    /*String tmp = br.readLine();
    while (tmp != null) {
        stringBuilder.append(tmp);
        tmp = br.readLine();
    }*/

    return stringBuilder.toString();
}

}