转载请注明出处：http://blog.csdn.net/bettarwang/article/details/41229955

       URL(Uniform Resource Locator)对象代表统一资源定位器，它是指向互联网资源的指针。URL由协议名、主机、端口和资源路径组件，即满足如下格式：

protocol://host:port/path

例如http://kan.sogou.com/dianying/就是一个URL地址。

(1)String getFile():获取此URL的资源名；

(2)String getHost():获取此URL的主机名；

(3)String getPath():获取此URL的路径部分；

(4)String getProtocol():获取此URL的协议名称；

(5)String getQuery():获取此URL的查询字符串部分；

(6)URLConnection openConnection():返回一个URLConnection对象，它表示URL所引用的远程对象与本进程的连接；

(7)InputStream openStream():打开与此URL的连接，并返回一个用于读取该URL资源的InputStream; 

下面以下载Baidu上的一张死神的图片为例，示范如何使用URL:

layout文件很简单，就两个button和一个ImageView，就不贴上来了，下面是源码：

public class MainActivity extends Activity implements View.OnClickListener{
	private static final String PIC_URL="http://pic7.nipic.com/20100528/4981527_163140644317_2.jpg";
	private static final int SHOW_IMAGE=0x123;
	private static final int SAVE_SUCC=0x124;
	private static final int SAVE_ERROR=0x125;
	
	Button showImageButton,saveImageButton;
	ImageView imageView;
	Bitmap bitmap;
	
	private Handler handler=new Handler()
	{
		@Override
		public void handleMessage(Message msg)
		{
			if(msg.what==SHOW_IMAGE)
			{
				imageView.setImageBitmap(bitmap);
			}
			else if(msg.what==SAVE_SUCC)
			{
				Toast.makeText(getBaseContext(), "图片保存成功", Toast.LENGTH_LONG).show();
			}
			else if(msg.what==SAVE_ERROR)
			{
				Toast.makeText(getBaseContext(), "图片保存出错", Toast.LENGTH_LONG).show();
			}
		}
	};
	
	private void initView()
	{
		showImageButton=(Button)findViewById(R.id.showImageButton);
		saveImageButton=(Button)findViewById(R.id.saveImageButton);
		imageView=(ImageView)findViewById(R.id.imageView);
	}
	
	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		
		initView();
		showImageButton.setOnClickListener(this);
		saveImageButton.setOnClickListener(this);
	}

	@Override
	public boolean onCreateOptionsMenu(Menu menu) {
		// Inflate the menu; this adds items to the action bar if it is present.
		getMenuInflater().inflate(R.menu.main, menu);
		return true;
	}

	private void showImage()
	{
		new Thread()
		{
			@Override
			public void run()
			{
				try 
				{
					URL url = new URL(PIC_URL);
					InputStream is=url.openStream();
					bitmap=BitmapFactory.decodeStream(is);
					handler.sendEmptyMessage(SHOW_IMAGE);
		            is.close();
				} 
				catch(Exception e) 
				{
					// TODO Auto-generated catch block
					e.printStackTrace();
				}
			}
		}.start();
		
	}
	
	public void saveImage()
	{
		new Thread()
		{
			@Override
			public void run()
			{
				try		
				{
					URL url=new URL(PIC_URL);
					InputStream is=url.openStream();
					BufferedInputStream bis=new BufferedInputStream(is);
					
					String filePath="animation.png";
					FileOutputStream fos=getBaseContext().openFileOutput(filePath,MODE_PRIVATE);
					BufferedOutputStream bos=new BufferedOutputStream(fos);
					
					byte[]buff=new byte[32];
					int hasRead=0;
					
					while((hasRead=bis.read(buff))>0)
					{
						bos.write(buff,0,hasRead);
					}
					
					
					bos.close();
					fos.close();
					
					bis.close();
					is.close();
					
				    handler.sendEmptyMessage(SAVE_SUCC);
				}
				catch(Exception ex)
				{
					handler.sendEmptyMessage(SAVE_ERROR);
					ex.printStackTrace();
				}
			}
		}.start();
	}
	
	@Override
	public void onClick(View v) {
		// TODO Auto-generated method stub
		switch(v.getId())
		{
		case R.id.showImageButton:
			showImage();
			break;
		case R.id.saveImageButton:
			saveImage();
			break;
		}
	}

}

Android中的网络编程系列(一):URLConnection