［Android基础］Android中使用HttpURLConnection

HttpURLConnection继承了URLConnection，因此也可以向指定网站发送GET请求、POST请求。它在URLConnetion的基础上提供了如下便捷的方法。

int getResponseCode():获取服务器的响应代码。
String getResponseMessage():获取服务器的访问信息。
String getRequestMethod():获取发送请求的方法。
void setRequestMethod(String method):设置发送请求的方法。
我们通过两个例子来体会一下：
一、将网站的内容显示在界面上：
1、创建一个WebView

<WebView
        android:id="@+id/webView"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true" />

2、MainActivity.java

public class MainActivity extends Activity {

    private WebView webview;
    //通过Handler在子线程更新主界面的UI
    private Handler handler = new Handler();
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        webview = (WebView) findViewById(R.id.webView);
        new HttpThread("http://www.sina.com", webview, handler).start();
    }
}

3、创建一个子线程

public class HttpThread extends Thread {
    private String url;
    private WebView webview;
    private Handler handler;
    //通过构造函数传三个参数
    public HttpThread(String url, WebView webView, Handler handler) {
        this.url = url;
        this.webview = webView;
        this.handler = handler;
    }
    }
    @Override
    public void run() {
        try {
            URL httpUri = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) httpUri.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");   
            final StringBuffer sb = new StringBuffer();
            BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream()));
            String str;
            while((str = reader.readLine()) != null)
            {
                sb.append(str);
            }
            handler.post(new Runnable() {

                @Override
                public void run() {
                //将数据加载到webview中
                    webview.loadData(sb.toString(), "text/html;charset=utf-8", null);
                }
            });
        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }
}

4、在AndroidManifest中添加权限：
android:name=”android.permission.INTERNET”

二、根据URL地址下载一张图片
1、创建一个webview

<ImageView 
        android:id="@+id/imageView1"
        android:layout_width="match_parent"
        android:layout_height="match_parent"/>

2、MainActivity.java

public class MainActivity extends Activity {

    private Handler handler = new Handler();
    private ImageView imageView;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        imageView = (ImageView) findViewById(R.id.imageView1);
        new     HttpThread("http://img5.duitang.com/uploads/item/201410/23/20141023211631_VKmfz.jpeg", imageView, handler).start();
    }

3、创建一个子线程

public class HttpThread extends Thread {
    private String url;
    private Handler handler;
    private ImageView imageView;
    public HttpThread(String url, ImageView imageView, Handler handler) {
        this.url = url;
        this.imageView = imageView;
        this.handler = handler;
    }
    @Override
    public void run() {
        try {
            URL httpUri = new URL(url);
            HttpURLConnection conn = (HttpURLConnection) httpUri.openConnection();
            conn.setReadTimeout(5000);
            conn.setRequestMethod("GET");
            //设置可以读取到输入流
            conn.setDoInput(true);
            InputStream in = conn.getInputStream();
            FileOutputStream out = null;
            String fileName = String.valueOf(System.currentTimeMillis());
            File downloadFile = null;
            if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))
            {
                //获得SDcard的目录文件
                File parent = Environment.getExternalStorageDirectory();
                downloadFile = new File(parent, fileName);
                out = new FileOutputStream(downloadFile);
            }
            //缓冲区
            byte[] b = new byte[2 * 1024];
            int len;
            if(out != null)
            {
                while((len = in.read(b)) != -1)
                {
                    out.write(b, 0, len);
                }
            }
            final Bitmap bitmap = BitmapFactory.decodeFile(downloadFile.getAbsolutePath());
            handler.post(new Runnable() {

                @Override
                public void run() {
                    imageView.setImageBitmap(bitmap);
                }
            });
        } catch (MalformedURLException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        } catch (IOException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    }

4、在AndroidManifest中添加权限：
android:name=”android.permission.WRITE_EXTERNAL_STORAGE”

这样下载的图片就显示在界面上了。