第五章：Android开发之联网

1、OKhttp     常用
2、retrofit     常用
3、volley       常用
4、XUtils        偶尔
5、HttpURLConnection   不常用
6、HttpClient                    不常用

 需要

1、创建URL对象
     URL url = new URL(path);
2、利用url的openConnection方法返回HttpUrlConnection对象
     HttpURLConnection connection = (HttpURLConnection) url.openConnection();
3、设置请求方式
     connection.setRequestMethod("GET");

4、设置连接超时
     connection.setConnectTimeout(5 * 1000);
5、获得返回的输入流
      InputStream inputStream = connection.getInputStream();
6、关闭连接
     connection.disconnection（）；

String path = "http://49.232.114.172:8080/yunying/qufumanage/getList.json";
        try {
            URL url = new URL(path);
            //获得httpUrlConnection
            HttpURLConnection connection = (HttpURLConnection) url.openConnection();
            //设置请求的方式为get
            connection.setRequestMethod("GET");
            //设置连接的时间为5秒
            connection.setConnectTimeout(5 * 1000);
            //如果responseCode=200时
            if (connection.getResponseCode() == 200) {
                //获取输入流
                InputStream inputStream = connection.getInputStream();
            }

        } catch (IOException e) {
            e.printStackTrace();
        }

1、创建ByteArrayOutputStream对象
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
2、创建byte[]和int len
      byte[] bytes = new byte[1024];
      int len = 0;
3、将输入流读到byte[]字节数组里
       while ((len = inputStream.read(bytes)) != -1) {
                    outputStream.write(bytes, 0, len);
                }
4、关闭流和链接

1、创建ByteArrayOutputStream对象
    ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
2、创建byte[]和int len
      byte[] bytes = new byte[1024];
      int len = 0;
3、将输入流读到byte[]字节数组里
       while ((len = inputStream.read(bytes)) != -1) {
                    outputStream.write(bytes, 0, len);
                }
4、关闭流和链接

               ByteArrayOutputStream outputStream = new ByteArrayOutputStream();
                byte[] bytes = new byte[1024];
                int len = 0;
                //将输入流读到byte[]字节数组里
                while ((len = inputStream.read(bytes)) != -1) {
                    outputStream.write(bytes, 0, len);
                }
                outputStream.close();
                 connection.disconnect();
                return new String(outputStream.toByteArray());

“http://49.232.114.172:8080/yunying/qufumanage/login.php”      
1、创建URL对象
     URL url = new URL(path);
2、利用url的openConnection方法返回HttpUrlConnection对象
     HttpURLConnection connection = (HttpURLConnection) url.openConnection();
3、设置请求方式
     connection.setRequestMethod("POST");

String data = "username="+ URLEncoder.encode("root","UTF-8")
                    +"&password="+URLEncoder.encode("root123456","UTF-8");

OutputStream outputStream = httpURLConnection.getOutputStream();
outputStream.write(data.getBytes());
//刷新此输出流并写出所有的输出字节
outputStream.flush();

            InputStream inputStream = httpURLConnection.getInputStream();
            ByteArrayOutputStream output = new ByteArrayOutputStream();
            byte[] bytes = new byte[1024];
            int lent = 0;
            while ((lent =inputStream.read(bytes)) != -1){
                output.write(bytes,0,lent);
            }
            String ss  = new String(output.toByteArray());

            outputStream.close();
            output.close();
            inputStream.close();
            httpURLConnection.disconnect();

android.os.NetworkOnMainThreadException
在Android 4.0以上，网络连接不能放在主线程上，不然就会报错android.os.NetworkOnMainThreadException。但是4.0下版本可以不会报错。

解决办法——创建子线程

    new Thread(new Runnable() {
                    @Override
                    public void run() {
                        
                    }
                }).start();

一、gradle配置文件中

android{
            defaultConfig{
                  useLibrary "org.apache.http.legacy"
                   }
       }

一、gradle配置文件中

android{
            defaultConfig{
                  useLibrary "org.apache.http.legacy"
                   }
       }

 private void getHttpClient(){
        HttpClient client = new DefaultHttpClient(); //获取HttpClient对象
        String url = "http://49.232.114.172:8080/yunying/qufumanage/login.php";
        HttpGet httpGet = new HttpGet(url);  //获取httpget对象
        try {
            HttpResponse response = client.execute(httpGet);//执行后返回HttpResponse
            HttpEntity entity = response.getEntity();
            String string = EntityUtils.toString(entity,"UTF-8");
            Log.d("TAG", "string==" + string);
        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    异常：android.os.NetworkOnMainThreadException

     new Thread(new Runnable() {
                    @Override
                    public void run() {
                        
                    }
                }).start();

        String path = "http://49.232.114.172:8080/yunying/qufumanage/login.php";
        HttpClient httpClient = new DefaultHttpClient(); //获取httpClient对象
        HttpPost httpPost = new HttpPost(path); //获取HttpPost对象
        List pairs = new ArrayList<>();  //添加参数
        pairs.add(new BasicNamevaluePair("username","root"));
        pairs.add(new BasicNamevaluePair("password","root123456"));

        try {
            httpPost.setEntity(new UrlEncodedFormEntity(pairs, HTTP.UTF_8)); //获得实体
            HttpResponse execute = httpClient.execute(httpPost); //执行请求
            String s = EntityUtils.toString(execute.getEntity()); //把内容转换成String
            Log.d("TAG",s);

        }  catch (Exception e) {
            e.printStackTrace();
        }