Android Jamendo开源在线音乐播放器源码分析五 网络连接模块的分析

程序中实现网络连接和获取网络数据是通过JamendoGet2Api这个接口中的方法实现的，他的实现类是JamendoGet2ApiImpl.这里就从getPopularAlbumsWeek()这个获取本周最受欢迎的专辑为例分析如何实现的，其实这个返回的数据就是在HomeActivity中最上面显示的Gallery中的数据。



这个图还真是不会画，索性就将用到的相关类都列出来。

@Override
	public Album[] getPopularAlbumsWeek() throws JSONException, WSError {
		
		String jsonString = doGet("id+name+url+image+rating+artist_name/album/json/?n=20&order=ratingweek_desc");
		if (jsonString == null)
			return null;
		
		try {
			JSONArray jsonArrayAlbums = new JSONArray(jsonString); 
			return AlbumFunctions.getAlbums(jsonArrayAlbums);
		} catch (NullPointerException e) {
			e.printStackTrace();
			throw new JSONException(e.getLocalizedMessage());
		}
	}

首先通过doGet方法根据指定的url通过HTTP协议获取网络数据

private static String GET_API = "http://api.jamendo.com/get2/";

private String doGet(String query) throws WSError{
	return Caller.doGet(GET_API + query);
}

/**
	 * Performs HTTP GET using Apache HTTP Client v 4
	 * 
	 * @param url
	 * @return
	 * @throws WSError 
	 */
	public static String doGet(String url) throws WSError{
		
		String data = null;
		if(requestCache != null){
			data = requestCache.get(url);
			if(data != null){
				Log.d(JamendoApplication.TAG, "Caller.doGet [cached] "+url);
				return data;
			}
		}
		
		URI encodedUri = null;
		HttpGet httpGet = null;
		
		try {
			encodedUri = new URI(url);
			httpGet = new HttpGet(encodedUri);
		} catch (URISyntaxException e1) {
			// at least try to remove spaces
			String encodedUrl = url.replace(' ', '+');
			httpGet = new HttpGet(encodedUrl);
			e1.printStackTrace();
		}
		
		// initialize HTTP GET request objects
		HttpClient httpClient = new DefaultHttpClient();
		HttpResponse httpResponse;
		
		try {
			// execute request
			try {
				httpResponse = httpClient.execute(httpGet);
			} catch (UnknownHostException e) {
				throw new WSError("Unable to access " + e.getLocalizedMessage());
			} catch (SocketException e){
				throw new WSError(e.getLocalizedMessage());
			}
			
			// request data
			HttpEntity httpEntity = httpResponse.getEntity();
			
			if(httpEntity != null){
				InputStream inputStream = httpEntity.getContent();
				data = convertStreamToString(inputStream);
				// cache the result
				if(requestCache != null){
					requestCache.put(url, data);
				}
			}
			
		} catch (ClientProtocolException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		
		Log.d(JamendoApplication.TAG, "Caller.doGet "+url);
		return data;
	}

根据返回的字符串数据创建JSONArray对象，然后根据AlbumFunctions的静态函数getAlbums将封装在JSONArray中字符串数据转换为Album对象，然后放在数组中返回

public class AlbumFunctions {
	
	public static Album[] getAlbums(JSONArray jsonArrayAlbums) throws JSONException {
		int n = jsonArrayAlbums.length();
		Album[] albums = new Album
;
		AlbumBuilder albumBuilder = new AlbumBuilder();
		
		for(int i=0; i < n; i++){
			albums[i] = albumBuilder.build(jsonArrayAlbums.getJSONObject(i));
		}
		
		return albums;
	}
}

albums[i] = albumBuilder.build(jsonArrayAlbums.getJSONObject(i));这里又使用到了封装Album对象的AlbumBuilder类

public class AlbumBuilder extends JSONBuilder<Album> {

	@Override
	public Album build(JSONObject jsonObject) throws JSONException {
		Album album = new Album();
		album.setImage(jsonObject.getString(root+"image"));
		album.setName(jsonObject.getString(root+"name"));
		album.setId(jsonObject.getInt(root+"id"));
		try {
			album.setArtistName(jsonObject.getString(root+"artist_name"));
		} catch (JSONException e) {
			// if we miss artist name an we are not in a subquery, abort!
			if(root.length()==0)
				throw e;
		}
		try {
			album.setRating(jsonObject.getDouble(root+"rating"));
		} catch (JSONException e) {
			album.setRating(-1);
		}
		return album;
	}
}

将JSONObject封装成Album对象

备注一：

以上只是对getPopularAlbumsWeek()这个函数的分析，但是具有通用性，其他的函数也都是这样实现的，首先通过HTTP根据url获取网络数据将流数据转换成字符串数据，然后通过JSON进行封装，然后通过相应的构造类如上面的AlbumBuilder将JSONArray中的JSONObject封装成相应的Album对象。

现在对这个代码最大的感觉是，这个代码写的很规范，无论是包结构还是类结构以及代码都非常规范，让人很容易就能了解整个程序的概貌，确实是值得好好学习的一个开源项目。