Android AsyncTask

private Button btn;
    private TextView tv;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        tv=(TextView) findViewById(R.id.tv);
        findViewById(R.id.btn).setOnClickListener(new OnClickListener() {
            
            @Override
            public void onClick(View v) {
                ReadURl("http://www.baidu.com");
                
            }
        });
    }
    
    
    public void ReadURl(String url){
        //初始化数据是传入的数据类型、处理过程中返回值的数据类型、处理完成后返回值的数据类型
        new AsyncTask<String, Float, String>() {

            //执行后台耗时操作
            @Override
            protected String doInBackground(String... params) {
                try {
                    URL url=new URL(params[0]);
                    URLConnection connection=url.openConnection();
                    long total=connection.getContentLength();
                    InputStream Istream=connection.getInputStream();
                    InputStreamReader isr=new InputStreamReader(Istream);
                    BufferedReader br=new BufferedReader(isr);
                    String line;
                    StringBuilder builder=new StringBuilder();
                    while ((line=br.readLine())!=null) {
                        builder.append(line);
                        publishProgress((float)builder.toString().length()/(float)total);    //调用publishProgress对外发布当前进度
                    }
                    br.close();
                    Istream.close();
                    return builder.toString();
                } catch (MalformedURLException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                } catch (IOException e) {
                    // TODO Auto-generated catch block
                    e.printStackTrace();
                }
                return null;
            }

            @Override
            protected void onCancelled() {
                // TODO Auto-generated method stub
                super.onCancelled();
            }

            @Override
            protected void onCancelled(String result) {
                // TODO Auto-generated method stub
                super.onCancelled(result);
            }

            @Override
            protected void onPostExecute(String result) {
                tv.setText(result);
                super.onPostExecute(result);
            }

            //在AsyncTask执行之前执行
            @Override
            protected void onPreExecute() {
                // TODO Auto-generated method stub
                super.onPreExecute();
            }

            //在AsyncTask执行的过程中，对外发布当前执行的进度
            @Override
            protected void onProgressUpdate(Float... values) {
                Toast.makeText(MainActivity.this, values[0]+"",Toast.LENGTH_SHORT).show();
                super.onProgressUpdate(values);
            }
            
        }.execute(url);
    }