异步操作

public class MainActivity extends AppCompatActivity {

    private Button btn_go;
    private ListView list_view;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        btn_go = findViewById(R.id.btn_go);
        list_view = findViewById(R.id.list_view);
        btn_go.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                 //执行异步任务
                MyTask myTask = new MyTask();
                myTask.execute("https://www.toutiao.com/api/pc/focus/");
            }
        });

    }
  class MyTask  extends  AsyncTask<String,Void,String>{

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

          StringBuilder builder = new StringBuilder();
          //1.创建url
          try {
              URL url = new URL(strings[0]);

              //2.打開连接
              HttpURLConnection urlConnection =(HttpURLConnection) url.openConnection();
              //3.设置
              urlConnection.setRequestMethod("GET");
              urlConnection.setReadTimeout(5000);
              urlConnection.setConnectTimeout(5000);
              //4.判断响应码
              if (urlConnection.getResponseCode() ==200){
                  //5.获取数据
                  InputStream inputStream = urlConnection.getInputStream();

                  BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream));

                  String str;
                  while ((str = reader.readLine())!= null){

                      builder.append(str);
                  }
                  reader.close();
              }
          } catch (Exception e) {
              e.printStackTrace();
          }
          return builder.toString();
      }
      //在进行网络请求得到数据之后，要操作的事件，，解析，更新Ui


      @Override
      protected void onPostExecute(String s) {
          // s:代表doInBackground 返回的数据
          Gson gson = new Gson();
          Result_bean result = gson.fromJson(s, Result_bean.class);
          List<Result_bean.DataBean.PcFeedFocusBean> list = result.getData().getPc_feed_focus();

          //更新UI的代码
        MyAdapter adapter = new MyAdapter (list,MainActivity.this);
          list_view.setAdapter(adapter);

      }
  }
}