//檢查網路連線狀況
public void chkNetwork(){
ConnectivityManager connMgr = (ConnectivityManager)getSystemService(Context.CONNECTIVITY_SERVICE);
NetworkInfo networkInfo = connMgr.getActiveNetworkInfo();
if (networkInfo != null && networkInfo.isConnected()) {
Log.d("CHECK_POINT", "網路連線中 " );
tv.setText("網路連線中");
//呼叫AsyncTask
new DownloadWebpageTask().execute();
} else {
Log.d("CHECK_POINT", "網路斷線 ");
tv.setText("網路斷線");
}
}
private class DownloadWebpageTask extends AsyncTask<String[],Integer,String[]>
{
@Override
protected String[] doInBackground(String[]... params) {
try {
return getWebData();
} catch (IOException e) {
e.printStackTrace();
return null;
}
}
@Override
//背景工作處理完"後"需作的事
protected void onPostExecute(String[] result) {
super.onPostExecute(result);
//進度BAR消失
ProgressBar pb=(ProgressBar)findViewById(R.id.progressBar);
pb.setVisibility(-1);
ArrayList<String> list=new ArrayList<String>();
for(int i=0;i<result.length;i++){
list.add(i,"recNo");
list.add(i,"sort");
}
ArrayAdapter<String> listA=new ArrayAdapter<String>(MainActivity.this,android.R.layout.simple_expandable_list_item_1,
list);
lv.setAdapter(listA);
}
//建立連線
private DefaultHttpClient getHttpClient(){
HttpParams httpparams = new BasicHttpParams();
int timeoutConnection = 5000;
HttpConnectionParams.setConnectionTimeout(httpparams,timeoutConnection);
int timeoutSocket=3000;
HttpConnectionParams.setSoTimeout(httpparams,timeoutSocket);
DefaultHttpClient dfaultHC = new DefaultHttpClient(httpparams);
return dfaultHC;
}
//取得網路資料
public String[] getWebData() throws IOException{
URL url=new URL("http://140.131.114.140/WebService/VB_test_browse.aspx");
HttpURLConnection conn = (HttpURLConnection)url.openConnection();
conn.setReadTimeout(10000);
conn.setConnectTimeout(15000);
conn.setRequestMethod("GET");
conn.setDoInput(true);
conn.connect();
BufferedReader reader = new BufferedReader(new InputStreamReader(conn.getInputStream(), "UTF-8"));
String jsonString= reader.readLine();
reader.close();
try {
Log.e("JSONdata",jsonString);
return (getJson(jsonString));
} catch (JSONException e) {
e.printStackTrace();
return null;
}
/*String url ="http://140.131.114.140/WebService/VB_test_browse.aspx";
HttpGet httpget = new HttpGet(url);
try{
HttpResponse httpresponse = getHttpClient().execute(httpget);
String jSONdata=EntityUtils.toString(httpresponse.getEntity());
Log.e("JSONdata",jSONdata);
return (getJson(jSONdata));
}catch(Exception err){
return null;
}*/
}
//將JSON字串解析
public String[] getJson(String jsonString) throws JSONException {
JSONArray jsonArr =new JSONArray(jsonString);
//JSONArray jsonArray = jsonObject.getJSONArray(jsonString);
String[] result = null;
//String[] recNo = null;
// String[] sort = null;
//String[] mMno =new String[jsonObject.length()];
// String[] mName = null ;
//String[] mTxt = null ;
//ArrayList<String> mpic =new ArrayList<String>(jsonObject.length());
//String[] itemArr = null ;
for(int i=0;i<jsonArr.length();i++)
{
try{
JSONObject lib = jsonArr.getJSONObject(i);
Log.e("recNo",lib.getString("recNo"));
result[i] +=lib.getString("recNo");
result[i] +=lib.getString("sort");
}catch(JSONException e){
e.printStackTrace();
}
}
return result;
}
堆栈跟踪：
04-30 16:13:09.803: W/dalvikvm(9714): threadid=11: thread exiting with uncaught exception (group=0x4160fd88)
04-30 16:13:09.803: E/AndroidRuntime(9714): FATAL EXCEPTION: AsyncTask #1
04-30 16:13:09.803: E/AndroidRuntime(9714): Process: com.example.jsonconnet, PID: 9714
04-30 16:13:09.803: E/AndroidRuntime(9714): java.lang.RuntimeException: An error occured while executing doInBackground()
04-30 16:13:09.803: E/AndroidRuntime(9714): at android.os.AsyncTask$3.done(AsyncTask.java:300)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.util.concurrent.FutureTask.finishCompletion(FutureTask.java:355)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.util.concurrent.FutureTask.setException(FutureTask.java:222)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.util.concurrent.FutureTask.run(FutureTask.java:242)
04-30 16:13:09.803: E/AndroidRuntime(9714): at android.os.AsyncTask$SerialExecutor$1.run(AsyncTask.java:231)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1112)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:587)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.lang.Thread.run(Thread.java:841)
04-30 16:13:09.803: E/AndroidRuntime(9714): Caused by: java.lang.NullPointerException
04-30 16:13:09.803: E/AndroidRuntime(9714): at com.example.jsonconnet.MainActivity$DownloadWebpageTask.getJson(MainActivity.java:179)
04-30 16:13:09.803: E/AndroidRuntime(9714): at com.example.jsonconnet.MainActivity$DownloadWebpageTask.getWebData(MainActivity.java:140)
04-30 16:13:09.803: E/AndroidRuntime(9714): at com.example.jsonconnet.MainActivity$DownloadWebpageTask.doInBackground(MainActivity.java:81)
04-30 16:13:09.803: E/AndroidRuntime(9714): at com.example.jsonconnet.MainActivity$DownloadWebpageTask.doInBackground(MainActivity.java:1)
04-30 16:13:09.803: E/AndroidRuntime(9714): at android.os.AsyncTask$2.call(AsyncTask.java:288)
04-30 16:13:09.803: E/AndroidRuntime(9714): at java.util.concurrent.FutureTask.run(FutureTask.java:237)
04-30 16:13:09.803: E/AndroidRuntime(9714): ... 4 more
答案 0 :(得分：2)
在getJson()中，您要为未初始化的result数组分配值。
考虑使用例如而是ArrayList<String>。