我是android新手。我创建了“重复调用JSON Web服务”应用程序。但它无法奏效。它意外停止了。在这里我使用Timer.Here我也给了代码。我如何清除这个意外的错误。请帮助我。应用程序被预期停止
这里也给出了错误。请更正错误
07-16 11:31:17.404: I/Process(275): Sending signal. PID: 275 SIG: 9
07-16 11:36:36.624: W/dalvikvm(285): Exception Ljava/lang/RuntimeException; thrown during Landroid/os/AsyncTask;.<clinit>
07-16 11:36:36.634: W/dalvikvm(285): threadid=7: thread exiting with uncaught exception (group=0x4001d800)
07-16 11:36:36.664: E/AndroidRuntime(285): FATAL EXCEPTION: Timer-0
07-16 11:36:36.664: E/AndroidRuntime(285): java.lang.ExceptionInInitializerError
07-16 11:36:36.664: E/AndroidRuntime(285): at com.example.repeat.MainActivity$1.run(MainActivity.java:51)
07-16 11:36:36.664: E/AndroidRuntime(285): at java.util.Timer$TimerImpl.run(Timer.java:289)
07-16 11:36:36.664: E/AndroidRuntime(285): Caused by: java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
07-16 11:36:36.664: E/AndroidRuntime(285): at android.os.Handler.<init>(Handler.java:121)
07-16 11:36:36.664: E/AndroidRuntime(285): at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421)
07-16 11:36:36.664: E/AndroidRuntime(285): at android.os.AsyncTask$InternalHandler.<init>(AsyncTask.java:421)
07-16 11:36:36.664: E/AndroidRuntime(285): at android.os.AsyncTask.<clinit>(AsyncTask.java:152)
07-16 11:36:36.664: E/AndroidRuntime(285): ... 2 more
07-16 11:41:36.887: I/Process(285): Sending signal. PID: 285 SIG:
代码：
Timer t;
private Context context;
private static String url = "http://docs.blackberry.com/sampledata.json";
private static final String TAG_VTYPE = "vehicleType";
private static final String TAG_VCOLOR = "vehicleColor";
private static final String TAG_FUEL = "fuel";
private static final String TAG_TREAD = "treadType";
private static final String TAG_OPERATOR = "approvedOperators";
private static final String TAG_NAME = "name";
private static final String TAG_POINTS = "experiencePoints";
ArrayList<HashMap<String, String>> jsonlist = new ArrayList<HashMap<String, String>>();
ListView lv ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
t=new Timer();
t.schedule(new TimerTask(){
@Override
public void run() {
// TODO Auto-generated method stub
new progress(MainActivity.this).execute();
}
}, 1000 * 15);
}
private class progress extends AsyncTask<String, Void, Boolean>{
private ProgressDialog dialog;
public progress(ListActivity activity){
Log.i("1", "Called");
context = activity;
dialog = new ProgressDialog(context);
}
protected void onPreExecute() {
this.dialog.setMessage("Progress start");
this.dialog.show();
}
protected void onPostExecute(final Boolean success) {
if (dialog.isShowing()) {
dialog.dismiss();
}
ListAdapter Adapter=new SimpleAdapter(context,jsonlist,
R.layout.list_item,new String[]{TAG_VTYPE, TAG_VCOLOR,
TAG_FUEL, TAG_TREAD },new int[] {
R.id.vehicleType,R.id.vehicleColor,R.id.fuel,
R.id.treadType});
setListAdapter(Adapter);
// selecting single ListView item
lv = getListView();
}
@Override
protected Boolean doInBackground(String... params) {
// TODO Auto-generated method stub
JSONParser parser=new JSONParser();
JSONArray array=parser.getJSONFromUrl(url);
for (int i = 0; i < array.length(); i++){
try{
JSONObject c= array.getJSONObject(i);
String vtype = c.getString(TAG_VTYPE);
String vcolor = c.getString(TAG_VCOLOR);
String vfuel = c.getString(TAG_FUEL);
String vtread = c.getString(TAG_TREAD);
HashMap<String, String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_VTYPE, vtype);
map.put(TAG_VCOLOR, vcolor);
map.put(TAG_FUEL, vfuel);
map.put(TAG_TREAD, vtread);
jsonlist.add(map);
}catch(JSONException e){
e.printStackTrace();
}
}
return null;
}
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
}
答案 0 :(得分：1)
您正在尝试在非UI线程中执行UI操作。从代码中看，这是因为您在这行代码中访问Context内的活动TimerTask：
t.schedule(new TimerTask(){
@Override
public void run() {
// TODO Auto-generated method stub
new progress(MainActivity.this).execute();
}
}, 1000 * 15);
编辑我会使用Handler代替Timer，因为您希望操作在后台定期运行。在处理程序的runnable中调用方法postDelayed，以便在经过指定的时间后再次运行进程，并使用UI处理程序更新UI。有关处理程序的信息，请参阅here。