舊方法：【Java】實作從html讀取JSON (應該是說在Android API 22之後Apache HTTP Client Removal，Http Get /post的方法被捨棄 )
新方法：以HttpURLConnection實作讀取
因為是要顯示在Android 手機上，那種耗時的網路連線、資料整理的動作並不能在main thread中做處理，所以需要額外開一條Thread在background做處理或是以AsyncTask。
在這裡使用AsyncTask來處理相關動作。(更多關於AsyncTask)
較重要的程式碼，如下：
AndroidManifest.xml
須加上
<uses-permission android:name="android.permission.INTERNET" />允許使用網路
<uses-permission android:name="android.permission.ACCESS_NETWORK_STATE">
</uses-permission>
允許檢查網路狀態FetchTask.java
public class FetchTask extends AsyncTask<String,Void,String> { interface OnFetchListener { public void OnAirDataFetchFinished(); } private OnFetchListener onFetchListener; public void setOnFetchListener(OnFetchListener listener) { onFetchListener =listener; } @Override protected String doInBackground(String... params) { DataFetcher.getInstance().fetchAirData(); return DataFetcher.getInstance().getResult(); } @Override protected void onPostExecute(String s) { onFetchListener.OnAirDataFetchFinished(); } }DataFetcher.java
public class DataFetcher { private StringBuilder airData = new StringBuilder(); private String path = "http://......"; private ArrayList<AirSiteObject> mItems; private DataFetcher() { } private static DataFetcher mFetcher; public static DataFetcher getInstance() { if (null == mFetcher) { mFetcher = new DataFetcher(); } return mFetcher; } public void fetchAirData() { HttpURLConnection httpURLConnection = null; try { URL url = new URL(path); httpURLConnection = (HttpURLConnection) url.openConnection(); httpURLConnection.connect(); int status = httpURLConnection.getResponseCode(); switch (status) { case 200: case 201: BufferedReader bufferedReader = new BufferedReader(new InputStreamReader(httpURLConnection.getInputStream(), "UTF-8")); String line; while ((line = bufferedReader.readLine()) != null) { airData.append(line + "\n"); } bufferedReader.close(); } } catch (IOException e) { e.printStackTrace(); } finally { if (httpURLConnection != null) { httpURLConnection.disconnect(); } } } public String getResult() { return airData.toString(); } //JSONParser public ArrayList<AirSiteObject> GetAirData(String result) { mItems =new ArrayList<AirSiteObject>(); JSONObject obj; try { JSONArray jsonArray = new JSONArray(result); for (int i = 0; i < jsonArray.length(); i++) { obj = jsonArray.getJSONObject(i); mItems.add(new AirSiteObject(obj)); } } catch (JSONException e) { Log.e("MYAPP", "unexpected JSON exception", e); } return mItems; } }MainActivity.java
private FetchTask mFetchAirDataTask;記得要
implements FetchTask.OnFetchListeneronCraete method
mFetchAirDataTask = new FetchTask();mFetchAirDataTask.setOnFetchListener(this);executeTask();
判斷網路是否正常
private void executeTask() { if (ToolsHelper.isNetworkAvailable(this)) { mFetchAirDataTask.execute(); } else { Toast.makeText(this, "未偵測到網路，請確認網路狀況。", Toast.LENGTH_LONG).show(); } }
實作OnFetchListener介面的OnAirDataFetchFinished method
@Override
public void OnAirDataFetchFinished() {
String result = DataFetcher.getInstance().getResult();
listView.setAdapter(new ViewItemAdapter(this, DataFetcher.getInstance().GetAirData(result)));
if (DataFetcher.getInstance().GetAirData(result).size() == 0) {
Toast.makeText(this, "資料讀取失敗，請稍候再重試。", Toast.LENGTH_LONG).show();
}
}
