接上文http://blog.csdn.net/tian_di_yi_jian/article/details/50437761。
從上文中,可以看出獲取到了Json數據,在MainActivity的封裝對象NewsBean繼續寫。首先我們把Json格式的字符串轉化爲JSONObject,取出data所對應的JSONArray,通過遍歷整個JSONArray來取出JSONObject,並取出每個所對應的值。由於JSONArray中每個元素都是一個JSONObject,所以可以從JSONArray中getJSONObject,取出每個JSONObject,最後將值傳遞給newsBean,但需要初始化newsBean,然後設置屬性,把newsBean塞到list中,最後將newsBeanList返回,完成JSON數據格式轉換成newsBean對象,這樣就可以再adapter中使用這些數據。
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);
}
// 將url對應的JSON格式數據轉化爲我們所封裝的NewsBean對象
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,可根據URL直接聯網獲取網絡數據
// 返回值的類型爲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;
}
// 通過InputStream解析網頁返回的數據
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;
}
// 顯示網絡的異步訪問
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一個NewsAsyncTask,將一個URL傳遞進去,實現對這個URL的異步訪問;接着,URL傳遞給了getJsonData()方法,並轉化爲NewsBean對象,再在AsyncTask中的onPostExecute()方法中將數據傳遞給NewsAdapter,通過NewsAdapter去構造listView的數據源並顯示出來。
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一個NewsAsyncTask,將一個URL傳遞進去,實現對這個URL的異步訪問;接着,URL傳遞給了getJsonData()方法,並轉化爲NewsBean對象,再在AsyncTask中的onPostExecute()方法中將數據傳遞給NewsAdapter,通過NewsAdapter去構造listView的數據源並顯示出來。