实现ListView图文混排 ——解析JSON到List中

接上文http://blog.csdn.net/tian_di_yi_jian/article/details/50437761。

从上文中，可以看出获取到了Json数据，在MainActivity的封装对象NewsBean继续写。首先我们把Json格式的字符串转化为JSONObject，取出data所对应的JSONArray，通过遍历整个JSONArray来取出JSONObject，并取出每个所对应的值。由于JSONArray中每个元素都是一个JSONObject，所以可以从JSONArray中getJSONObject，取出每个JSONObject，最后将值传递给newsBean，但需要初始化newsBean，然后设置属性，把newsBean塞到list中，最后将newsBeanList返回，完成JSON数据格式转换成newsBean对象，这样就可以再adapter中使用这些数据。

public class MainActivity extends Activity {
	private ListView listView;
	public static String URL = "http://www.imooc.com/api/teacher?type=4&num=30";

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		listView = (ListView) findViewById(R.id.lv_main);
		new NewsAsyncTask().execute(URL);
	}

	// 将url对应的JSON格式数据转化为我们所封装的NewsBean对象
	private List<NewsBean> getJsonData(String url) {
		List<NewsBean> newsBeansList = new ArrayList<NewsBean>();
		try {
			String jsonString = readStream(new URL(url).openStream());
			// 此句和url.openConnection().getInputStream()相同，可根据URL直接联网获取网络数据
			// 返回值的类型为InputStream
<span style="white-space:pre">			</span>JSONObject jsonObject;
			NewsBean newsBean;
			try {
				jsonObject = new JSONObject(jsonString);
				JSONArray jsonArray = jsonObject.getJSONArray("data");
				for (int i = 0; i < jsonArray.length(); i++) {
					jsonObject = jsonArray.getJSONObject(i);
					newsBean = new NewsBean();
					newsBean.newsIconUrl = jsonObject.getString("picSmall");
					newsBean.newsTitle = jsonObject.getString("name");
					newsBean.newsContent = jsonObject.getString("description");
					newsBeansList.add(newsBean);
				}
			} catch (JSONException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		} catch (IOException e) {
			e.printStackTrace();
		}
		return newsBeansList;
	}

	// 通过InputStream解析网页返回的数据
	private String readStream(InputStream is) {
		String result = "";
		InputStreamReader isr;
		try {
			String line = "";
			isr = new InputStreamReader(is, "utf-8");
			BufferedReader br = new BufferedReader(isr);
			while ((line = br.readLine()) != null) {
				result += line;
			}
		} catch (UnsupportedEncodingException e) {
			e.printStackTrace();
		} catch (IOException e) {
			e.printStackTrace();
		}
		return result;

	}

	// 显示网络的异步访问
	class NewsAsyncTask extends AsyncTask<String, Void, List<NewsBean>> {

		@Override
		protected List<NewsBean> doInBackground(String... params) {
			// TODO Auto-generated method stub
			return getJsonData(params[0]);
		}

		@Override
		protected void onPostExecute(List<NewsBean> newsBeans) {
			super.onPostExecute(newsBeans);
			NewsAdapter adapter = new NewsAdapter(MainActivity.this, newsBeans);
			listView.setAdapter(adapter);
		}
	}
}

首先在onCreate()方法中new一个NewsAsyncTask，将一个URL传递进去，实现对这个URL的异步访问；接着，URL传递给了getJsonData()方法，并转化为NewsBean对象，再在AsyncTask中的onPostExecute()方法中将数据传递给NewsAdapter，通过NewsAdapter去构造listView的数据源并显示出来。

public class NewsAdapter extends BaseAdapter {
	private List<NewsBean> list;
	private LayoutInflater layoutInflater;

	public NewsAdapter(Context context, List<NewsBean> data) {
		list = data;
		layoutInflater = LayoutInflater.from(context);
	}

	@Override
	public int getCount() {
		return list.size();
	}

	@Override
	public Object getItem(int position) {
		return list.get(position);
	}

	@Override
	public long getItemId(int position) {
		return position;
	}

	@Override
	public View getView(int position, View convertView, ViewGroup parent) {
		ViewHolder viewHolder = null;
		if (convertView == null) {
<span style="white-space:pre">			</span>viewHolder=new ViewHolder();
<span style="white-space:pre">			</span>convertView=layoutInflater.inflate(R.layout.item_layout, null);
			viewHolder.ivImage = (ImageView) convertView
					.findViewById(R.id.iv_image);
			viewHolder.tvTitle = (TextView) convertView
					.findViewById(R.id.tv_title);
			viewHolder.tvContent = (TextView) convertView
					.findViewById(R.id.tv_content);
			convertView.setTag(viewHolder);
		} else {
			viewHolder = (ViewHolder) convertView.getTag();
		}
		viewHolder.ivImage.setImageResource(R.drawable.ic_launcher);
		viewHolder.tvTitle.setText(list.get(position).newsTitle);
		viewHolder.tvContent.setText(list.get(position).newsContent);
		return convertView;
	}

	class ViewHolder {
		public TextView tvTitle, tvContent;
		public ImageView ivImage;
	}
}

首先在onCreate()方法中new一个NewsAsyncTask，将一个URL传递进去，实现对这个URL的异步访问；接着，URL传递给了getJsonData()方法，并转化为NewsBean对象，再在AsyncTask中的onPostExecute()方法中将数据传递给NewsAdapter，通过NewsAdapter去构造listView的数据源并显示出来。