HTTP Protocol

HttpURLConnection

• activity_main.xml

    <!--手机界面有限，需要这个控件来滚动展示内容-->
    <ScrollView
        android:layout_width="match_parent"
        android:layout_height="match_parent">
        <TextView
            android:layout_width="match_parent"
            android:layout_height="match_parent"
            android:id="@+id/textview0"/>
    </ScrollView>

• MainActivity.java

public class MainActivity extends Activity {


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        try {
            //实例化一个要访问的地址对象
            URL url = new URL("HTTP://360.net");
            //打开链接到url地址的连接通道，并强制转化成Http协议的连接类型
            HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
            //GET请求
            httpURLConnection.setRequestMethod("GET");
            //10s连接超时
            httpURLConnection.setConnectTimeout(10000);
            //从连接到的资源上读取时间不能超过5s
            httpURLConnection.setReadTimeout(5000);
            //从远程连接的地址上获取资源数据，流进到本地
            //BufferedReader: Reads text from a character-input stream
            InputStream in = httpURLConnection.getInputStream();
            BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in));
            //从BufferedReader对象中获取文本数据
            StringBuilder stringbuilder = new StringBuilder();
            String line;
            while ((line = bufferedReader.readLine()) != null){
                stringbuilder.append(line);
            }
            TextView text = (TextView)findViewById(R.id.textview0);
            text.setText(stringbuilder.toString());
        } catch (MalformedURLException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

• android.os.NetworkOnMainThreadException

官方：
The exception that is thrown when an application attempts to perform a networking operation on its main thread.
主线程内不能进行网络请求（早期版本还是可以的），尝试开启子线程进行这个工作

public class MainActivity extends Activity {

    //实例化一个Handler对象，并重写他的处理消息的方法，来处理我们发送的消息
    public Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 1:{
                    String string = (String) msg.obj;
                    TextView textview = (TextView)findViewById(R.id.textview0);
                    textview.setText(string);
                }
            }
        }
    };

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //开启子线程进行费时工作
        new Thread(new Runnable() {
            @Override
            public void run() {
                try {
                    //实例化一个要访问的地址对象
                    URL url = new URL("HTTP://360.net");
                    //打开链接到url地址的连接通道，并强制转化成Http协议的连接类型
                    HttpURLConnection httpURLConnection = (HttpURLConnection) url.openConnection();
                    //GET请求
                    httpURLConnection.setRequestMethod("GET");
                    //10s连接超时
                    httpURLConnection.setConnectTimeout(10000);
                    //从连接到的资源上读取时间不能超过5s
                    httpURLConnection.setReadTimeout(5000);
                    //从远程连接的地址上获取资源数据，流进到本地
                    //BufferedReader: Reads text from a character-input stream
                    InputStream in = httpURLConnection.getInputStream();
                    BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(in));
                    //从BufferedReader对象中获取文本数据
                    StringBuilder stringbuilder = new StringBuilder();
                    String line;
                    while ((line = bufferedReader.readLine()) != null){
                        stringbuilder.append(line);
                    }
                    //消息对象
                    Message message = new Message();
                    //消息标识符，方便接受者接收指定消息
                    message.what = 1;
                    //an arbitrary（任意） object to send to the recipient（接受者）.
                    message.obj = stringbuilder.toString();
                    handler.sendMessage(message);
                } catch (MalformedURLException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}

HttpClient(Interface)

HttpClient是 Apache 提供的 HTTP 网络访问接口，从一开始的时候就被引入到了 Android
API 中

• GET请求
  build.gradle

android {
    //主要在android字段下添加这一句
    useLibrary 'org.apache.http.legacy'
.....

MainActivity.java

public class MainActivity extends Activity {

    //实例化一个Handler对象，并重写他的处理消息的方法，来处理我们发送的消息
    public Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 1:{
                    String string = (String) msg.obj;
                    TextView textview = (TextView)findViewById(R.id.textview0);
                    textview.setText(string);
                }
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //开启子线程进行费时工作
        new Thread(new Runnable() {
            @Override
            public void run() {
                //Creates a new HTTP client
                HttpClient httpclient = new DefaultHttpClient();
                //实例化一个GET 请求对象
                HttpGet getRequest = new HttpGet("http://www.so.com");
                //客户端发起这个GET请求对象
                try {
                    httpclient.execute(getRequest);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }).start();
    }
}

• POST请求
  比GET请求只是多有一些参数数据
  MainActivity.java

public class MainActivity extends Activity {

    //实例化一个Handler对象，并重写他的处理消息的方法，来处理我们发送的消息
    public Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 1:{
                    String string = (String) msg.obj;
                    TextView textview = (TextView)findViewById(R.id.textview0);
                    textview.setText(string);
                }
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //开启子线程进行费时工作
        new Thread(new Runnable() {
            @Override
            public void run() {
                //Creates a new HTTP client
                HttpClient httpclient = new DefaultHttpClient();
                //实例化一个POST 请求对象
                HttpPost request = new HttpPost("https://mail.qq.com/cgi-bin/loginpage?autologin=n");
                //NameValuePair是一个接口，提供了获取键值对数据的功能
                ArrayList<NameValuePair> params = new ArrayList<NameValuePair>();
                //获取键值数据,拥有NameValuePair的类型
                params.add(new BasicNameValuePair("username","password"));
                try {
                    //对参数数据进行URL编码
                    UrlEncodedFormEntity entity = new UrlEncodedFormEntity(params, "utf-8");
                    //将编码后的数据实体放入请求中
                    request.setEntity(entity);
                    //发送请求,获取浏览器响应
                    HttpResponse httpresponse = (HttpResponse) httpclient.execute(request);
                    //查看返回的状态码
                    if (httpresponse.getStatusLine().getStatusCode() == 200){
                        Log.e("statuscode", "200");
//                        Toast.makeText(getApplicationContext(), "status code :200 ",Toast.LENGTH_LONG);
                    }else {
                        int codenumber = httpresponse.getStatusLine().getStatusCode();
//                        Toast.makeText(MainActivity.this, "status code :" + String.valueOf(codenumber),Toast.LENGTH_LONG);
                        Log.e("statuscode", String.valueOf(codenumber));
                    }
                    //将网站返回的数据，又消息传递给Handler
                    String responsecontent = EntityUtils.toString(httpresponse.getEntity());
                    Message message = new Message();
                    message.what = 1;
                    message.obj = responsecontent;
                    handler.sendMessage(message);
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        }).start();
    }
}

上面代码中注释了2句Toast，因为会报错java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()，很明显这是因为这个Toast内部应该创建handler来执行的

XML格式

千万不要少了eventType = xmlparse.next();这句里的next()方法，来推动解析往下进行

public class MainActivity extends Activity {

    //实例化一个Handler对象，并重写他的处理消息的方法，来处理我们发送的消息
    public Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 1:{
                    Toast.makeText(getApplicationContext(), "status code :200 ",Toast.LENGTH_LONG);
                    TextView textView = (TextView)findViewById(R.id.textview0);
                    textView.setText((String)msg.obj);
                }
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //开启子线程进行费时工作
        new Thread(new Runnable() {
            @Override
            public void run() {
                //Creates a new HTTP client
                HttpClient httpclient = new DefaultHttpClient();
                //实例化一个POST 请求对象
                HttpGet request = new HttpGet("http://10.91.35.22/aaa.xml");
                //NameValuePair是一个接口，提供了获取键值对数据的功能
                try {
                    //发送请求,获取浏览器响应
                    HttpResponse httpresponse = (HttpResponse) httpclient.execute(request);
                    //查看返回的状态码
                    if (httpresponse.getStatusLine().getStatusCode() == 200){
                        Log.e("statuscode", "200");
//                        Toast.makeText(getApplicationContext(), "status code :200 ",Toast.LENGTH_LONG);
                    }else {
                        int codenumber = httpresponse.getStatusLine().getStatusCode();
//                        Toast.makeText(MainActivity.this, "status code :" + String.valueOf(codenumber),Toast.LENGTH_LONG);
                        Log.e("statuscode", String.valueOf(codenumber));
                    }
                    //将网站返回的数据，又消息传递给Handler
                    String responsecontent = EntityUtils.toString(httpresponse.getEntity());
                    Message message = new Message();
                    message.what = 1;
                    message.obj = responsecontent;
                    handler.sendMessage(message);
                    xmlparse(responsecontent);
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        }).start();
    }

    public void xmlparse(String response){
        //这个对象使用来创建xml解析器
        try {
            XmlPullParserFactory xmlfactory = XmlPullParserFactory.newInstance();
            //XML解析器
            XmlPullParser xmlparse = xmlfactory.newPullParser();
            //给解析器传入响应数据流
            xmlparse.setInput(new StringReader(response));
            //返回当前事件的类型
            int eventType = xmlparse.getEventType();
            //标签
            String id = "";
            String name = "";
            String version = "";
            //END_DOCUMENT类型表示xml文件逻辑结束
            //也就是只要xml没有解析结束，继续执行
            while(eventType != XmlPullParser.END_DOCUMENT) {
                //节点名称
                String nodename = xmlparse.getName();
                //开始解析某个节点
                switch (eventType) {
                    //开始读取标签
                    case XmlPullParser.START_TAG: {
                        if ("id".equals(nodename)) {
                            id = xmlparse.nextText();
                            Log.e("[+] id: ",id);
                        } else if ("name".equals(nodename)) {
                            name = xmlparse.nextText();
                            Log.e("[+] name: ",name);
                        } else if ("version".equals(nodename)) {
                            version = xmlparse.nextText();
                            Log.e("[+] version: ",version);
                        }
                        break;
                    }
                    case XmlPullParser.END_TAG:{
                        Log.e("xml", "解析结束");
                        break;
                    }
                    default:
                        break;
                }
                //解析下一个节点
                eventType = xmlparse.next();
            }
        } catch (XmlPullParserException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

SAX解析

用到了一个类org.xml.sax.helpers.DefaultHandler
重写这五个方法来处理节点的数据
defaultHandler.java

public class defaultHandler extends org.xml.sax.helpers.DefaultHandler{
    private StringBuilder id;
    private StringBuilder name;
    private StringBuilder version;
    private String elementName;
    @Override
    //开始xml文档解析
    public void startDocument() throws SAXException {
        id = new StringBuilder();
        name = new StringBuilder();
        version = new StringBuilder();
    }

    @Override
    public void startElement(String uri, String localName, String qName, Attributes attributes) throws SAXException {
        Log.e("[+] ", "开始解析节点");
        //节点名称
        elementName = localName;
    }

    @Override
    //接收节点里数据的通知
    public void characters(char[] ch, int start, int length) throws SAXException {
        Log.e("[+] ", "处理节点里的数据");
       if("id".equals(elementName)){
           id.append(ch, start, length);
       }else if("name".equals(elementName)){
           name.append(ch, start, length);
       }else if("version".equals(elementName)){
           version.append(ch, start, length);
       }
    }

    @Override
    public void endElement(String uri, String localName, String qName) throws SAXException {
            Log.e("[+] ", "处理节点结束");
    }

    @Override
    public void endDocument() throws SAXException {
        Log.e("[+] id", "id is"+ id.toString());
        Log.e("[+] name", "name is"+ name.toString());
        Log.e("[+] version", "version is"+ version.toString());
        Log.e("[+] ", "xml文件解析完毕");
        //释放缓冲区
        id.setLength(0);
        name.setLength(0);
        version.setLength(0);
    }
}

MainActivity.java

public class MainActivity extends Activity {

    //实例化一个Handler对象，并重写他的处理消息的方法，来处理我们发送的消息
    public Handler handler = new Handler(){
        @Override
        public void handleMessage(Message msg) {
            switch (msg.what){
                case 1:{
                    Toast.makeText(getApplicationContext(), "status code :200 ",Toast.LENGTH_LONG);
                    TextView textView = (TextView)findViewById(R.id.textview0);
                    textView.setText((String)msg.obj);
                }
            }
        }
    };


    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        //开启子线程进行费时工作
        new Thread(new Runnable() {
            @Override
            public void run() {
                //Creates a new HTTP client
                HttpClient httpclient = new DefaultHttpClient();
                //实例化一个POST 请求对象
                HttpGet request = new HttpGet("http://10.91.35.22/aaa.xml");
                //NameValuePair是一个接口，提供了获取键值对数据的功能
                try {
                    //发送请求,获取浏览器响应
                    HttpResponse httpresponse = (HttpResponse) httpclient.execute(request);
                    //查看返回的状态码
                    if (httpresponse.getStatusLine().getStatusCode() == 200){
                        Log.e("statuscode", "200");
//                        Toast.makeText(getApplicationContext(), "status code :200 ",Toast.LENGTH_LONG);
                    }else {
                        int codenumber = httpresponse.getStatusLine().getStatusCode();
//                        Toast.makeText(MainActivity.this, "status code :" + String.valueOf(codenumber),Toast.LENGTH_LONG);
                        Log.e("statuscode", String.valueOf(codenumber));
                    }
                    //将网站返回的数据，又消息传递给Handler
                    String responsecontent = EntityUtils.toString(httpresponse.getEntity());
                    Message message = new Message();
                    message.what = 1;
                    message.obj = responsecontent;
                    handler.sendMessage(message);
                    xmlparse(responsecontent);
                } catch (UnsupportedEncodingException e) {
                    e.printStackTrace();
                } catch (ClientProtocolException e) {
                    e.printStackTrace();
                } catch (IOException e) {
                    e.printStackTrace();
                }

            }
        }).start();
    }

    public void xmlparse(String response){
        //这个对象使用来创建xml解析器
        try {
            SAXParserFactory saxfactory = SAXParserFactory.newInstance();
            //XML解析器
            SAXParser saxparse = saxfactory.newSAXParser();
            //开始解析,传入参数，和解析方式
            saxparse.parse(new InputSource(new StringReader(response)), new defaultHandler());

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

JSON解析

``
出现一个小问题就是android4.0之后，json检测utf bom头

用BOM: Zero Width No-Break Space来表明是UTF编码，看下面的代码，是需要检测编码的

    public JSONTokener(String in) {
        // consume an optional byte order mark (BOM) if it exists
        if (in != null && in.startsWith("\ufeff")) {
            in = in.substring(1);
        }
        this.in = in;
    }

添加bom头，继续报错...type org.json.JSONObject cannot be converted to JSONArray

response = "\ufeff"+ response;

根据 相似问题org.json.JSONObject cannot be converted to JSONArray in android，知道从json对象中先获取json数组，改成如下代码，还是报错，info of type org.json.JSONObject cannot be converted to JSONArray

        JSONObject jsondata = new JSONObject(response);
        JSONArray jsonArray = jsondata.getJSONArray("info");
        for (int i = 0; i<jsonArray.length(); i++){
            JSONObject jsonobj = jsonArray.getJSONObject(i);
            Log.e("获取的json数据：info",(String) jsonobj.get("name"));
        }

跟踪源代码运行，终于发现，这里JSON数据有5个字段，键值info对应的值还是一个JSON对象（可以将大括号{}看成一个JSON对象)

2018-10-09_202029.png
2018-10-09_202029.png

继续向下打开，发现JSONArray对象指的是键值对中的值为一个列表，所以代码需要多解析几步，上面哪些错误是不用理会的

2018-10-09_202820.png

    public void jsonParse(String response) throws JSONException {
        JSONObject jsondata = new JSONObject(response);
        JSONArray jsonArray = jsondata.getJSONObject("info").getJSONArray("builtin_modules");
        for (int i = 0; i<jsonArray.length(); i++){
            Log.e("获取的json数据：info",(String) jsonArray.get(i));
        }
    }

2018-10-09_203404.png

GSON解析Google提供的第三方库

1、先下载GJSON的jar包下载地址
2、将jar包放入libs目录下，然后右键这个jar包，选择add as libary选项，即可

2018-10-09_205314.png
3、代码

你真的会用Gson吗?Gson使用指南（一）
person.java

public class person {
    private String name;
    private int age;
    private String ads;
//省略setter、getter、constructor
    }

MainActivity.java

        //一个拥有名字和年龄的对象
        person p1 = new person("kingkary", 56);
        //获取一个Gson对象
        Gson gson = new Gson();
        //将这个对象中的数据转成json类型
        Log.e("JSON数据",gson.toJson(p1));

2018-10-09_214814.png