get请求

package com.example.unit3_requestdata_asynctask_demo;

    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;    import android.os.AsyncTask;    import android.os.Bundle;    import android.app.Activity;    import android.app.ProgressDialog;    import android.view.Menu;    import android.view.View;    import android.widget.TextView;

public class MainActivity extends Activity {

private ProgressDialog pd;private TextView tv;@Overrideprotected void onCreate(Bundle savedInstanceState) {    super.onCreate(savedInstanceState);    setContentView(R.layout.activity_main);    tv = (TextView) findViewById(R.id.tv);}public void requestjoke(View v){    //1.构造出来    MyTask myTask=new MyTask();    myTask.execute("http://japi.juhe.cn/joke/content/list.from?sort=asc&page=1&pagesize=10&time=1418816972&key=fae8fe09dba9d27aab24308a21b53bce");}//定义异步任务//1.Params   一般是请求的网址 String Void //2.Progress 请求网络数据的进度 一般是  Integer void //3.Result   请求网络数据得到的结果 json xml  String Void 自定义一个对象  List<?> class MyTask extends AsyncTask<String, Void, String>{    //请求网络 的代码    @Override    protected String doInBackground(String... arg0) {//String... 可变长类型 相当于String[]        String str="";        try {            //1.根据路径创建一个URL对象            URL url=new URL(arg0[0]);            //2.打开连接            HttpURLConnection openConnection = (HttpURLConnection)url.openConnection();            //3.进行设置            openConnection.setRequestMethod("GET");            openConnection.setReadTimeout(3000);            openConnection.setConnectTimeout(3000);            //4.得到响应码            int code=openConnection.getResponseCode();            if(code==200){                //5.得到数据                InputStream inputStream = openConnection.getInputStream();                str=streamToString(inputStream);            }        } catch (MalformedURLException e) {            // TODO Auto-generated catch block            e.printStackTrace();        } catch (IOException e) {            // TODO Auto-generated catch block            e.printStackTrace();        }        return str;    }    //在执行操作之前    @Override    protected void onPreExecute() {        // TODO Auto-generated method stub        super.onPreExecute();        //创建一个进度对话框，并显示出来        pd=new ProgressDialog(MainActivity.this);        pd.setProgressStyle(ProgressDialog.STYLE_SPINNER);//小圆  设置样式        pd.setMessage("正在请求，请稍后...");        pd.show();    }    //在执行操作之后    @Override    protected void onPostExecute(String result) {        // TODO Auto-generated method stub        super.onPostExecute(result);        if(pd!=null && pd.isShowing()){            //关闭对话框            pd.dismiss();        }        //显示         tv.setText(result);    }}/** * 将字节流信息的内容读取出来 * @param is * @return */public String streamToString(InputStream is){    StringBuilder builder=new StringBuilder();    BufferedReader reader=new BufferedReader(new InputStreamReader(is));    String con;    try {        while((con=reader.readLine())!=null){            builder.append(con);        }        reader.close();    } catch (IOException e) {        // TODO Auto-generated catch block        e.printStackTrace();    }    return builder.toString();}

}

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"        xmlns:tools="http://schemas.android.com/tools"        android:layout_width="match_parent"        android:layout_height="match_parent"        android:paddingBottom="@dimen/activity_vertical_margin"        android:paddingLeft="@dimen/activity_horizontal_margin"        android:paddingRight="@dimen/activity_horizontal_margin"        android:paddingTop="@dimen/activity_vertical_margin"        tools:context=".MainActivity" ><Button        android:layout_width="match_parent"                android:layout_height="wrap_content"                android:text="请求笑话数据"                android:onClick="requestjoke"                android:id="@+id/btn"/><TextView android:layout_width="match_parent"        android:layout_height="match_parent"        android:id="@+id/tv"        android:layout_below="@+id/btn"        android:textColor="#00f"/></RelativeLayout>