我有Service和AsyncTask，由于检查服务器上的更新。如果获得一些数据，它必须重新执行，如果没有，则必须重新执行。所以我的AsyncTask实现是：
private class DklabExecute extends AsyncTask<Void, String, Void> {
int count;
Calendar calendar = Calendar.getInstance();
java.util.Date now = calendar.getTime();
java.sql.Timestamp currentTimestamp = new java.sql.Timestamp(now.getTime());
String url = "http://192.168.0.250:81/?identifier=nspid_"+md5(LoginActivity.passUserId)+
",nspc&ncrnd="+Long.toString(currentTimestamp.getTime());
HttpGet rplPost = new HttpGet(url);
protected Void doInBackground(Void... args)
{
Log.i("service count", Integer.toString(count));
count ++;
Log.i("md5 func", md5(LoginActivity.passUserId));
String testData = "http://192.168.0.250/app_dev.php/api/comet/testOrder/";
JSONParser parser = new JSONParser();
DefaultHttpClient testClient = new DefaultHttpClient();
DefaultHttpClient rplClient = new DefaultHttpClient();
try {
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("", ""));
HttpGet httpTest = new HttpGet(testData);
httpTest.setHeader("Cookie", CookieStorage.getInstance().getArrayList().get(0).toString());
rplPost.setHeader("Cookie", CookieStorage.getInstance().getArrayList().get(0).toString());
try {
httpResponse = rplClient.execute(rplPost);
}
catch (ClientProtocolException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
} catch (IOException e1) {
// TODO Auto-generated catch block
e1.printStackTrace();
}
Header[] head = httpResponse.getAllHeaders();
Log.i("http Response",httpResponse.toString());
for (Header one:head)
{
Log.i("headers",one.toString());
}
Log.i("response code", Integer.toString(httpResponse.getStatusLine().getStatusCode()));
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
BufferedReader reader = new BufferedReader(new InputStreamReader(is));
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null)
{
sb.append(line);// + "n");
}
try
{
is.close();
}
catch (IOException e)
{
e.printStackTrace();
}
json = sb.toString();
Log.i("rpl response",json);
if (new JSONArray(json) != null)
jArr = new JSONArray(json);
else
this.cancel(true);
JSONObject toObj = jArr.getJSONObject(0);
JSONObject data = toObj.getJSONObject(KEY_DATA);
if (data.has(KEY_ORDER))
{
for (Order a : ServiceMessages.orderExport)
{
Log.i("service before list", a.toString());
}
Log.i(" ", " ");
for (Order a : DashboardActivityAlt.forPrint)
{
Log.i("before dashboard list", a.toString());
}
JSONObject jsonOrder = data.getJSONObject(KEY_ORDER);
Gson gson = new Gson();
Order orderObj= gson.fromJson(jsonOrder.toString(), Order.class);
try
{
for (ListIterator<Order> itr = orderExport.listIterator(); itr.hasNext();)
{
Order a = itr.next();
Log.i("order count", a.toString());
if(orderObj.getOrderid()==a.getOrderid())
{
Log.i("Service","order was changed");
a = orderObj;
someMethod("Your order "+ orderObj.getTitle() + " was changed");
}
else
{
Log.i("Service","order"+ orderObj.getTitle()+" was added");
// DashboardActivityAlt.forPrint.add(0, orderObj);
ServiceMessages.orderExport.add(0,orderObj);
Log.i("status",Integer.toString(orderObj.getProcess_status().getProccessStatusId()));
someMethod("Your order "+ orderObj.getTitle() + " was added");
}
}
}
catch (Exception e)
{
e.printStackTrace();
}
for (Order a : ServiceMessages.orderExport)
{
Log.i("service after list", a.toString());
}
Log.i(" ", " ");
for (Order a : DashboardActivityAlt.forPrint)
{
Log.i("after dashboard list", a.toString());
}
// intentOrder.putParcelableArrayListExtra("ordersService", orderExport);
sendBroadcast(intentOrder);
Log.i("after parse order",orderObj.toString());
Log.i("orders after updating",DashboardActivityAlt.orders.toString() );
}
else if (data.has(KEY_MESSAGE))
{
JSONObject jsonMessage = data.getJSONObject(KEY_MESSAGE);
Gson gson = new Gson();
Log.i("messages before parse", jsonMessage.toString());
for (Order a: DashboardActivityAlt.forPrint)
{
Log.i("messages count", Integer.toString(a.getCusThread().getMessages().size()));
}
Log.i("disparse message",jsonMessage.toString());
Message message = gson.fromJson(jsonMessage.toString(),Message.class);
Log.i("incomming message",message.toString());
JSONObject jsonThread = jsonMessage.getJSONObject(KEY_THREAD);
Threads thread = gson.fromJson(jsonThread.toString(),Threads.class);
Log.i("incomming thread",thread.toString());
Order orderChanged = new Order();
String orderName = null;
for(Order as : DashboardActivityAlt.forPrint)
{
if (as.getOrderid() == thread.getTreadOrder().getOrderid())
{
orderName = as.getTitle();
orderChanged = as;
Log.i("messages count after", Integer.toString(as.getCusThread().getMessages().size()));
}
}
Log.i("orderchanged",orderChanged.toString());
someMethod("Your order "+ thread.getTreadOrder().getTitle() + " was changed. Message was added");
orderChanged.getCusThread().addMessage(message);
sendBroadcast(intentMessage);
Log.i("messages service", "before sleep");
Log.i("messages service", "after sleep");
}
else
{
this.cancel(true);
}
}
catch (IllegalStateException e2) {
// TODO Auto-generated catch block
e2.printStackTrace();
} catch (IOException e2) {
rplClient.getConnectionManager().shutdown();
testClient.getConnectionManager().shutdown();
someMethod("You've lost internet connection. You should try later.");
e2.printStackTrace();
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return null;
}
protected void onPostExecute(Void bitmap) {
this.cancel(true);
new DklabExecute().execute();
}
}
如果我将一些数据发送到服务器，它会通过rpl服务器以JSON格式返回给我。一切都运行良好，但问题是当我从服务器获取一些数据时，在onPostExecute()方法中重新执行了AsyncTask，并且在我的订单列表中重复了一两次数据。如果我不重新执行AsyncTask，则仅在onStartCommand()方法中进行监听，但不是永久性的。请告诉我如何以最佳方式实现这一点......
答案 0 :(得分：1)
如果是服务，则没有理由使用AsyncTask。 构建AyncTasks是为了在原始线程（通常是UI线程）上传回内容，但服务没有这些内容。
我建议您使用ScheduledExecutorService而不是http://developer.android.com/reference/java/util/concurrent/ScheduledExecutorService.html
private ScheduledExecutorService executor;
// call those on startCommand
executor = Executors.newSingleThreadScheduledExecutor();
executor.scheduleWithFixedDelay(run, 250,3000, TimeUnit.MILLISECONDS);
并让Runnable完成工作
private Runnable run = new Runnable() {
@Override
public void run() {
// do your network stuff
}
};
并且不要忘记在服务停止时取消所有内容
executor.shutdown();
或者在循环中使用线程，你可以：
boolean isRunning;
// this on your start
Thread t = new Thread(run);
isRunning = true;
t.start();
runnable
private Runnable run = new Runnable() {
@Override
public void run() {
while(isRunning){
// do your network stuff
}
}
};
再次，不要忘记在服务结束时完成：
isRunning = false;