HTTP协议访问网络——HttpURLConnection

HttpURLConnection的使用
HttpURLConnection的实例
主函数

布局

总结

单线程下载和多线程下载及网络连接
MainActivity

IndexActivity

DownLoadActivity

MultiThread

activity_mainxml

activity_indexxml

activity_downloadxml

AndroidManifestxml的配置

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

[code]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

[code]<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

[code]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

[code]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

[code]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

[code]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

[code]<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

[code]<?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

[code]<?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

[code]<?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

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