Network Programming series in Android (1): URLConnection

Network Programming series in Android (1): URLConnection

 

The URL (Uniform Resource Locator) object represents a unified Resource Locator, which is a pointer to Internet resources. The URL consists of the protocol name, host, port, and resource Path Components:

 

protocol://host:port/path

 

 

For example, http://kan.sogou.com/dianying/#a urladdress.

URL provides multiple constructor methods for creating URL objects. The main methods provided by URL are as follows:

 

(1) String getFile (): gets the Resource Name of this URL;

(2) String getHost (): Get the host name of this URL;

(3) String getPath (): obtains the path of the URL;

(4) String getProtocol (): Get the protocol name of this URL;

(5) String getQuery (): Obtain the query String of this URL;

(6) URLConnection openConnection (): returns a URLConnection object, which indicates the connection between the remote object referenced by the URL and the local process;

(7) InputStream openStream (): Open the connection to this URL and return an InputStream used to read the URL resource;

The following uses the example of downloading an image of death on Baidu to demonstrate how to use a URL:

The layout file is very simple. Two buttons and one ImageView are not attached. The following is the source code:

 

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 () {@ Overridepublic void handleMessage (Message msg) {if (msg. what = SHOW_IMAGE) {imageView. setImageBitmap (bitmap);} else if (msg. what = SAVE_SUCC) {Toast. makeText (getBaseContext (), the image is saved successfully, Toast. LENGTH_LONG ). show ();} else if (msg. what = SAVE_ERROR) {Toast. makeText (getBaseContext (), image saving error, 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) ;}@ Overrideprotected void onCreate (Bundle savedInstanceState) {super. onCreate (savedInstanceState); setContentView (R. layout. activity_main); initView (); showImageButton. setOnClickListener (this); saveImageButton. setOnClickListener (this) ;}@ Overridepublic 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 () {@ Overridepublic 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 blocke. printStackTrace ();}}}. start ();} public void saveImage () {new Thread () {@ Overridepublic 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 () ;}@ Overridepublic void onClick (View v) {// TODO Auto-generated method stubswitch (v. getId () {case R. id. showImageButton: showImage (); break; case R. id. saveImageButton: saveImage (); break ;}}}

Data/com. android. in urlsample/files, note that the order of closing the stream is the opposite to that of creating the stream. Otherwise, an exception is thrown.