HTTP协议访问网络——HttpURLConnection

HttpURLConnection的使用

1、首先要获取到HttpURLConnection的实例，一般只需要new出一个URL对象，并传入目标的网络地址，然后调用一下openConnection()方法即可。

URL url=new URL(“http://www.baidu.com“);
HttpURLConnection connection=(HttpURLConnection)url.openConnection();

2、得到了HttpURLConnection的实例之后，我们可以设置一下HTTP请求所使用的方法。常用的方法主要有两个，GET和POST。GET表示希望从服务器那里获取数据，而POST则表示希望提交数据给服务器，写法如下：

connection.setRequestMethod(“GET”);

3、现在我们可以进行一些自由的定制了，比如设置连接超时。读取超时的毫秒数，以及服务器希望得到的一些消息头等。示例如下：

connection.setConnectTimeout(8000);
connection.setReadTimeout(8000);

4、调用getInputStream()方法就可以获取到服务器返回的输入流，剩下的就是对输入流进行读取，如下所示：

InputStream is=connection.getInputStream();

5、最后调用disconnect()方法将这个HTTP连接关闭掉。如下所示：

connection.disconnect();

HttpURLConnection的实例

主函数

public class MainActivity extends AppCompatActivity implements View.OnClickListener {    public static final int SHOW_RESPPONSE=0X12;    private Button mButtonSendRequest;    private TextView mTextViewResponse;    private Handler handler=new Handler(){        @Override        public void handleMessage(Message msg) {            switch (msg.what){                case SHOW_RESPPONSE:                    String content= (String) msg.obj;                    mTextViewResponse.setText(content);                    break;            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mButtonSendRequest= (Button) findViewById(R.id.send_request);        mTextViewResponse= (TextView) findViewById(R.id.response);        mButtonSendRequest.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.send_request:                new Thread(new Runnable() {                    @Override                    public void run() {                        HttpURLConnection connection=null;                        try {                            URL url=new URL("http://www.baidu.com");                            connection= (HttpURLConnection) url.openConnection();                            connection.setRequestMethod("GET");                            connection.setConnectTimeout(8000);                            connection.setReadTimeout(8000);                            InputStream is=connection.getInputStream();                            //下面对获取到的输入流进行读取                            BufferedReader br=new BufferedReader(new InputStreamReader(is));                            StringBuilder builder=new StringBuilder();//这里用StringBuilder和StringBuffer都可以                            String line=br.readLine();                            while (line!=null) {                                builder.append(line);                                line = br.readLine();                            }                                Message msg=handler.obtainMessage();                                msg.what=SHOW_RESPPONSE;                                msg.obj=builder.toString();                                handler.sendMessage(msg);                        } catch (MalformedURLException e) {                            e.printStackTrace();                        } catch (IOException e) {                            e.printStackTrace();                        }                    }                }).start();                break;        }    }

布局

<LinearLayout 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:paddingLeft="@dimen/activity_horizontal_margin"    android:paddingRight="@dimen/activity_horizontal_margin"    android:paddingTop="@dimen/activity_vertical_margin"    android:paddingBottom="@dimen/activity_vertical_margin"    android:orientation="vertical" tools:context=".MainActivity">    <Button        android:id="@+id/send_request"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:text="Send Request "/>    <ScrollView        android:layout_width="match_parent"        android:layout_height="match_parent">        <TextView            android:id="@+id/response"            android:layout_width="match_parent"            android:layout_height="wrap_content" />    </ScrollView>    </LinearLayout>

总结

1、在按钮点击事件中先是开启了一个子线程，然后在子线程里使用了HttpURLConnection发出一条HTTP请求，请求的目的地址就是百度的首页，接着利用BufferedReader对服务器返回的流进行读取，并将结果存放到builder中。最后在放入Message对象中，至于这里为什么要使用Message对象——是因为子线程中无法对UI进行操作。我们希望可以将服务器返回的内容显示到界面上，所以创建了UI个Message对象并使用Handler将它发送出去，之后在handlerMessage（）方法中对这条Message进行处理，最终取出结果并设置到TextView上。

2、在布局中我使用了一个新控件——ScrollView，由于手机屏幕空间一般较小，有时候过多的内容一屏是显示不下的，借助ScrollView控件的话就可以允许我们以滚动的形式查看屏幕以外的那部分内容。另外，布局中还设置了一个Button和一个TextView，Button用于发送HTTP请求，TextView用于将服务器返回的数据显示出来。

单线程下载和多线程下载、及网络连接

MainActivity

public class MainActivity extends AppCompatActivity implements View.OnClickListener{private Button mButtonContent;    private TextView mTextCiewContent;    private static final int URL_CONNECT=0X123;    private Handler handler=new Handler(){        @Override        public void handleMessage(Message msg) {            super.handleMessage(msg);            switch (msg.what){                case URL_CONNECT:                    String content= (String) msg.obj;                    mTextCiewContent.setText(content);                    break;            }        }    };    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_main);        mButtonContent= (Button) findViewById(R.id.button_content);        mButtonContent.setOnClickListener(this);        mTextCiewContent= (TextView) findViewById(R.id.textview_content);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.button_content:                new Thread(new Runnable() {                    @Override                    public void run() {                        ConnectURL();                    }                }).start();                break;        }    }    private void ConnectURL() {        try {//            URL url=new URL("http://192.168.0.102:8080/MyServerTest/MyTestServerlet");            URL url=new URL("http://www.360.com");            URLConnection connection=url.openConnection();            InputStream is=connection.getInputStream();            BufferedReader br=new BufferedReader(new InputStreamReader(is));            String line=br.readLine();            StringBuffer buffer=new StringBuffer();            while(line!=null){                Log.d("", line);                buffer.append(line);                line=br.readLine();            }            Message msg=handler.obtainMessage();            msg.what=URL_CONNECT;            msg.obj=buffer.toString().trim();            handler.sendMessage(msg);            br.close();            is.close();        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }}

IndexActivity

public class IndexActivity extends AppCompatActivity implements View.OnClickListener{   private Button mButtonURLConnection;    private Button mButtonDownload;    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);      setContentView(R.layout.activity_index);        mButtonURLConnection= (Button) findViewById(R.id.button_urlconnection);        mButtonDownload= (Button) findViewById(R.id.button_download);        mButtonURLConnection.setOnClickListener(this);        mButtonDownload.setOnClickListener(this);    }    @Override    public void onClick(View v) {        switch (v.getId()){            case R.id.button_download:                Intent intentDowanload=new Intent(getApplicationContext(),DownLoadActivity.class);                startActivity(intentDowanload);                break;            case R.id.button_urlconnection:                Intent intentUrl=new Intent(getApplicationContext(),MainActivity.class);                startActivity(intentUrl);                break;        }    }}

DownLoadActivity

public class DownLoadActivity extends AppCompatActivity implements View.OnClickListener {    private Button mButtonSingle;    private Button mButtonMore;    private ProgressBar mProgressBar;    private int length;    private static final int SEND_SUM = 0X123;    private Handler handler = new Handler() {        @Override        public void handleMessage(Message msg) {            switch (msg.what){                case SEND_SUM:                    mProgressBar.setProgress(msg.arg1*100/length);                    break;            }        }    };    @Override    public void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_download);        mButtonSingle = (Button) findViewById(R.id.button_single);        mButtonMore = (Button) findViewById(R.id.button_more);        mButtonSingle.setOnClickListener(this);        mButtonMore.setOnClickListener(this);        mProgressBar = (ProgressBar) findViewById(R.id.progressbar);    }    @Override    public void onClick(View v) {        switch (v.getId()) {            case R.id.button_single:                SingleDownloadTask singleDownloadTask = new SingleDownloadTask();                singleDownloadTask.execute();                break;            case R.id.button_more:                new Thread(new Runnable() {                    @Override                    public void run() {                        try {                            String urlPath = "http://192.168.0.43:8080/www/music/sj.mp3";                            URL url = new URL(urlPath);                            URLConnection connection = url.openConnection();                             length = connection.getContentLength();                            File file = new File(Environment.getExternalStorageDirectory(), "aa.mp3");                            if (!file.exists()) {                                file.createNewFile();                            }                            MultiThread[] threads = new MultiThread[5];                            for (int i = 0; i < 5; i++) {                                MultiThread thread = null;                                if (i == 4) {                                    thread = new MultiThread(length / 5 * 4, length, urlPath, file.getAbsolutePath());                                } else {                                    thread = new MultiThread(length / 5 * i, length / 5 * ((i + 1)-1), urlPath, file.getAbsolutePath());                                }                                thread.start();                                threads[i] = thread;                            }                            boolean isFinish = true;                            while (isFinish) {                                int sum = 0;                                for (MultiThread thread : threads) {                                    sum += thread.getSum();                                }                                Message msg = handler.obtainMessage();                                msg.what = SEND_SUM;                                msg.arg1 = sum;                                handler.sendMessage(msg);                                if (sum + 10 >= length) {                                    isFinish = false;                                }                                Thread.sleep(1000);                            }                        } catch (MalformedURLException e) {                            e.printStackTrace();                        } catch (IOException e) {                            e.printStackTrace();                        } catch (InterruptedException e) {                            e.printStackTrace();                        }                    }                }).start();                break;        }    }    class SingleDownloadTask extends AsyncTask<String, Integer, String> {        @Override        protected void onProgressUpdate(Integer... values) {//...三个点表示参数个数不定            super.onProgressUpdate(values);            mProgressBar.setProgress((int) (values[0] * 100.0 / values[1]));//sum表示数组[0],length表示数组[1]        }        @Override        protected void onPostExecute(String s) {            super.onPostExecute(s);        }        @Override        protected String doInBackground(String... params) {            try {                URL url = new URL("http://192.168.0.43:8080/www/music/sj.mp3");                URLConnection connection = url.openConnection();//打开连接                 length = connection.getContentLength();//得到内容总长度                InputStream is = connection.getInputStream();//得到输入流                //将Environment.getExternalStorageDirectory()路径下的takingmeaway.mp3文件实例化                File file = new File(Environment.getExternalStorageDirectory(), "takingmeaway.mp3");                if (!file.exists()) {                    file.createNewFile();                }                FileOutputStream outputStream = new FileOutputStream(file);//输出流将文件输入到file                byte[] array = new byte[1024];                int sum = 0;                int index = is.read(array);//从输入流中读出文件放在数组array中                while (index != -1) {                    outputStream.write(array, 0, index);//将数组中的文件写入到file中，从数组的第一个即下标号0处开始读入                    sum += index;                    publishProgress(sum, length);//将参数传入onProgressUpdate中，设置进度条                    index = is.read(array);                }                outputStream.flush();                outputStream.close();                is.close();            } catch (MalformedURLException e) {                e.printStackTrace();            } catch (IOException e) {                e.printStackTrace();            }            return null;        }    }}

MultiThread

public class MultiThread extends Thread{    private int sum=0;    private long start;    private long end;    private String urlPath;    private String filePath;    public MultiThread(long start,long end, String url, String filePath) {        this.start=start;        this.end=end;        this.urlPath=url;        this.filePath=filePath;    }    public int getSum(){        return sum;    }    @Override    public void run() {        try {            URL url=new URL(urlPath);            URLConnection connection=url.openConnection();            connection.setAllowUserInteraction(true);//允许用户进行交互            //setRequestProperty是告诉服务器 我的客户端的配置、需求.这里设置了从开始到结束的范围            connection.setRequestProperty("Range", "bytes=" + start + "-" + end);            InputStream is=connection.getInputStream();            File file=new File(filePath);            if (!file.exists()){                file.createNewFile();            }            //RandomAccessFile是用来访问那些保存数据记录的文件的            RandomAccessFile randomAccessFile=new RandomAccessFile(file,"rw");           randomAccessFile.seek(start);//在文件里移动用seek()方法;            byte []array=new byte[1024];            int index=is.read(array);             sum=0;            while (index!=-1){                randomAccessFile.write(array,0,index);                sum+=index;                index=is.read(array);            }            randomAccessFile.close();            is.close();        } catch (MalformedURLException e) {            e.printStackTrace();        } catch (IOException e) {            e.printStackTrace();        }    }}

activity_main.xml

<ScrollView 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:orientation="vertical"    tools:context=".MainActivity"><LinearLayout    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical">    <Button        android:id="@+id/button_content"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="连接网络"        />    <TextView        android:id="@+id/textview_content"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="内容"/></LinearLayout>   </ScrollView>

activity_index.xml

<?xml version="1.0" encoding="utf-8"?><ScrollView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent"    android:layout_height="match_parent"><LinearLayout    android:orientation="vertical"    android:layout_width="match_parent"    android:layout_height="match_parent">    <Button        android:id="@+id/button_urlconnection"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="HTTPurlconnectionn"/>    <Button        android:id="@+id/button_download"        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="下载文件"/></LinearLayout></ScrollView>

activity_download.xml

<?xml version="1.0" encoding="utf-8"?><ScrollView xmlns:android="http://schemas.android.com/apk/res/android"    android:layout_width="match_parent" android:layout_height="match_parent">    <LinearLayout        android:layout_width="match_parent"        android:layout_height="match_parent"        android:orientation="vertical">      <ProgressBar          android:id="@+id/progressbar"          android:layout_width="match_parent"          android:layout_height="25dp"          android:layout_marginTop="20dp"          style="@style/Base.Widget.AppCompat.ProgressBar.Horizontal"/>        <Button            android:id="@+id/button_single"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="单线程下载"/>        <Button            android:id="@+id/button_more"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="多线程下载"/>    </LinearLayout></ScrollView>

AndroidManifest.xml的配置

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"package="com.example.administrator.myurlconnection" >    <!--连接网络的权限--><uses-permission android:name="android.permission.INTERNET"></uses-permission>    <!--可写入存储卡的权限 --><uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>    <!--可读存储卡的权限 --><uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"></uses-permission><application    android:allowBackup="true"    android:icon="@mipmap/ic_launcher"    android:label="myurlconnection"    android:theme="@style/AppTheme" >    <activity android:name=".IndexActivity">        <intent-filter>            <action android:name="android.intent.action.MAIN" />            <category android:name="android.intent.category.LAUNCHER" />        </intent-filter>    </activity>    <activity android:name=".MainActivity"></activity>    <activity android:name=".DownLoadActivity"></activity></application></manifest>

总结：代码中用到了单线程和多线程，以及用来传递消息的Handler类、设置进度条的方法、RandomAccessFile类（是用来访问那些保存数据记录的文件的）和它的相关方法，比如： RandomAccessFile randomAccessFile=new RandomAccessFile(file,”rw”);
randomAccessFile.seek(start); 当然上面程序的很多方法我都已经给出了相应的解释，只要耐心看程序就会看懂滴*-*