在我的项目中打开应用程序AsyncTask启动并从json页面获取数据时我添加if for check network是否可用。但是如果网络访问和启动AsyncTask网络后差或关闭突然加力关闭。这是JsonParser类：
public class JSONParser {
static InputStream is = null;
static JSONObject jObj = null;
static String json = "";
public Context mContext;
// constructor
public JSONParser(Context _context) {
mContext = _context;
}
public JSONObject getJSONFromUrl(String url) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpPost httpPost = new HttpPost(url);
HttpResponse httpResponse = httpClient.execute(httpPost);
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONObject(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
和AsyncTask是这样的：
public class myAsyncTask extends AsyncTask<String ,String,JSONObject> {
@Override
protected void onPreExecute(){
if(b == 0)
_func.showProgress("on");
}
@Override
protected JSONObject doInBackground(String... params) {
jParser = new JSONParser(mContext);
jObject = jParser.getJSONFromUrl(url);
return jObject;
}
@Override
protected void onPostExecute(JSONObject jObject){
try {
if (jObject.getString("code").equals("200")) {
if (b == 0)
_func.showProgress("off");
try {
jArray = jObject.getJSONArray("result");
for (int i = 0; i < jArray.length(); i++) {
JSONObject rItem = jArray.getJSONObject(i);
title.add(rItem.getString("title").toString());
id.add(rItem.getString("id").toString());
}
} catch (JSONException e) {
_func.toast(mContext.getString(R.string.nothingToShow));
}
}
}
} catch (JSONException e1) {
e1.printStackTrace();
}
}
}
当互联网变得糟糕或正在关闭时，我如何能够停止asyncTask ??? ：（
12-12 18:18:03.940 15313-15339/ir.jobcenterplace.app.jobfinder E/Buffer Error: Error converting result java.lang.NullPointerException: lock == null
12-12 18:18:03.940 15313-15339/ir.jobcenterplace.app.jobfinder E/JSON Parser: Error parsing data org.json.JSONException: End of input at character 0 of
12-12 18:18:03.940 15313-15313/ir.jobcenterplace.app.jobfinder D/AndroidRuntime: Shutting down VM
12-12 18:18:03.940 15313-15313/ir.jobcenterplace.app.jobfinder W/dalvikvm: threadid=1: thread exiting with uncaught exception (group=0x4187ada0)
12-12 18:18:03.940 15313-15313/ir.jobcenterplace.app.jobfinder E/AndroidRuntime: FATAL EXCEPTION: main
Process: ir.jobcenterplace.app.jobfinder, PID: 15313
java.lang.NullPointerException
at ir.jobcenterplace.app.jobfinder.myAsyncTask.onPostExecute(myAsyncTask.java:87)
at ir.jobcenterplace.app.jobfinder.myAsyncTask.onPostExecute(myAsyncTask.java:24)
at android.os.AsyncTask.finish(AsyncTask.java:632)
at android.os.AsyncTask.access$600(AsyncTask.java:177)
at android.os.AsyncTask$InternalHandler.handleMessage(AsyncTask.java:645)
at android.os.Handler.dispatchMessage(Handler.java:102)
at android.os.Looper.loop(Looper.java:146)
at android.app.ActivityThread.main(ActivityThread.java:5679)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:515)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:1291)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:1107)
at dalvik.system.NativeStart.main(Native Method)