我正在开发一个基本的聊天类应用程序，目前我正在运行代码，如下所示：
class GetMsgs extends AsyncTask<String, String, String> {
@Override
protected void onPreExecute() {
super.onPreExecute();
pDialog = new ProgressDialog(MsgViewActivity.this);
pDialog.setMessage("Fetching..");
pDialog.setIndeterminate(false);
pDialog.setCancelable(true);
pDialog.show();
}
@Override
protected String doInBackground(String... arg0) {
Intent intent = getIntent();
String tmp = intent.getStringExtra("Header");
List<NameValuePair> params = new ArrayList<NameValuePair>();
params.add(new BasicNameValuePair("Header", tmp));
// getting JSON Object
// Note that create product url accepts POST method
json = jsonParser.makeHttpRequest(url,
"POST", params);
return null;
}
protected void onPostExecute(String file_url) {
pDialog.dismiss();
ListView listView_msg = (ListView)findViewById(R.id.MsgView);
int j = 0;
String Msgs[];
try{
msgs = json.getJSONArray("Messages");
auths = json.getJSONArray("Authors");
id = json.getString("ID");
Msgs = new String[msgs.length()];
for(int i = 0; i < msgs.length(); i++){
if ((msgs.getString(i) != "")&&(auths.getString(i) != "")){
Msgs[j++] = auths.getString(i) + " : " + msgs.getString(i);
}
}
msg_adapter = new ArrayAdapter<String>(MsgViewActivity.this,
android.R.layout.simple_list_item_1, Msgs);
listView_msg.setChoiceMode(ListView.CHOICE_MODE_SINGLE);
listView_msg.setAdapter(msg_adapter);
}
catch(JSONException e){
e.printStackTrace();
}
}
}
这样：
new GetMsgs().execute();
当我在Android的事件开始时运行它，甚至点击按钮时，它的工作和完美表现。但是当我尝试以给定间隔运行它来刷新消息屏幕时，应用程序崩溃。
我尝试过我在这里找到的方法： i）How to set a timer in android ii）Android timer? How-to?
但我不断遇到应用程序崩溃。
由于某种原因，是否无法以特定的时间间隔运行代码，或者是否存在实施问题。
一些帮助将不胜感激。
logcat的：
04-06 11:45:40.396: V/Provider/Setting(5644): invalidate [system]: current 286 != cached 0
04-06 11:45:40.406: V/Provider/Setting(5644): from db cache, name = sound_effects_enabled value = 1
04-06 11:45:40.407: V/InputMethodManager(5644): focusOut: android.widget.EditText@41c27350 mServedView=android.widget.EditText@41c27350 winFocus=true
04-06 11:45:40.456: D/dalvikvm(5644): create interp thread : stack size=32KB
04-06 11:45:40.456: D/dalvikvm(5644): create new thread
04-06 11:45:40.456: D/dalvikvm(5644): new thread created
04-06 11:45:40.456: D/dalvikvm(5644): update thread list
04-06 11:45:40.456: D/dalvikvm(5644): threadid=11: interp stack at 0x52af2000
04-06 11:45:40.457: D/dalvikvm(5644): threadid=11: created from interp
04-06 11:45:40.457: D/dalvikvm(5644): start new thread
04-06 11:45:40.457: D/dalvikvm(5644): threadid=11: notify debugger
04-06 11:45:40.457: D/dalvikvm(5644): threadid=11 (AsyncTask #1): calling run()
04-06 11:45:40.529: V/InputMethodManager(5644): Starting input: view=android.widget.TabHost@41c23ab0
04-06 11:45:40.529: V/InputMethodManager(5644): Starting input: tba=android.view.inputmethod.EditorInfo@41c68d80 ic=null
04-06 11:45:40.529: V/InputMethodManager(5644): START INPUT: android.widget.TabHost@41c23ab0 ic=null tba=android.view.inputmethod.EditorInfo@41c68d80 controlFlags=#100
04-06 11:45:40.531: V/InputMethodManager(5644): Starting input: Bind result=InputBindResult{com.android.internal.view.IInputMethodSession$Stub$Proxy@41c698a0 com.touchtype.swiftkey/com.touchtype.KeyboardService #4807}
04-06 11:45:40.534: V/InputMethodManager(5644): onWindowFocus: null softInputMode=288 first=true flags=#1820002
04-06 11:45:40.534: V/InputMethodManager(5644): Not IME target window, ignoring
04-06 11:45:40.540: D/dalvikvm(5644): threadid=12: interp stack at 0x537ff000
04-06 11:45:40.542: D/libc-netbsd(5644): getaddrinfo: myphptestsite.bugs3.com get result from proxy >>
04-06 11:45:40.549: I/System.out(5644): propertyValue:true
04-06 11:45:40.550: I/System.out(5644): [socket][0] connection /93.188.160.82:80;LocalPort=45152(0)
04-06 11:45:40.551: I/System.out(5644): [CDS]connect[/93.188.160.82:80] tm:90
04-06 11:45:40.552: D/Posix(5644): [Posix_connect Debug]Process com.example.groupchat :80
04-06 11:45:40.925: I/SurfaceTextureClient(5644): [STC::queueBuffer] (this:0x51247728) fps:11.83, dur:1014.51, max:391.89, min:15.83
04-06 11:45:41.562: I/SurfaceTextureClient(5644): [STC::queueBuffer] (this:0x52afe8e0) fps:54.92, dur:1001.41, max:60.19, min:7.67
04-06 11:45:41.912: I/System.out(5644): [socket][/100.69.10.243:45152] connected
04-06 11:45:41.913: I/System.out(5644): [CDS]rx timeout:0
04-06 11:45:41.922: I/System.out(5644): >doSendRequest
04-06 11:45:41.930: I/System.out(5644): <doSendRequest
04-06 11:45:42.573: I/SurfaceTextureClient(5644): [STC::queueBuffer] (this:0x52afe8e0) fps:56.37, dur:1011.19, max:23.49, min:12.03
04-06 11:45:43.365: D/dalvikvm(5644): GC_CONCURRENT freed 211K, 12% free 13462K/15171K, paused 2ms+2ms, total 17ms
04-06 11:45:43.372: D/OpenGLRenderer(5644): Flushing caches (mode 0)
04-06 11:45:43.439: I/SurfaceTextureClient(5644): [STC::queueBuffer] (this:0x51247728) fps:5.57, dur:2514.10, max:2279.30, min:12.11
04-06 11:45:43.455: V/InputMethodManager(5644): onWindowFocus: android.widget.ListView@41c2fd98 softInputMode=16 first=false flags=#1810100
04-06 11:45:43.456: V/InputMethodManager(5644): Starting input: view=android.widget.ListView@41c2fd98
04-06 11:45:43.456: V/InputMethodManager(5644): Starting input: tba=android.view.inputmethod.EditorInfo@41bf0db8 ic=null
04-06 11:45:43.456: V/InputMethodManager(5644): START INPUT: android.widget.ListView@41c2fd98 ic=null tba=android.view.inputmethod.EditorInfo@41bf0db8 controlFlags=#101
04-06 11:45:43.458: V/InputMethodManager(5644): Starting input: Bind result=InputBindResult{com.android.internal.view.IInputMethodSession$Stub$Proxy@41c0ada8 com.touchtype.swiftkey/com.touchtype.KeyboardService #4808}
04-06 11:45:45.101: D/VelocityTracker(5644): Couldn't open '/dev/touch' (No such file or directory)
04-06 11:45:45.101: D/VelocityTracker(5644): tpd read x fail: Bad file number
04-06 11:45:45.101: D/VelocityTracker(5644): tpd read y fail: Bad file number
04-06 11:45:45.260: I/SurfaceTextureClient(5644): [STC::queueBuffer] (this:0x51247728) fps:1.65, dur:1821.68, max:1796.98, min:9.99
04-06 11:45:46.205: V/Provider/Setting(5644): from settings cache , name = sound_effects_enabled value = 1
04-06 11:45:46.262: I/SurfaceTextureClient(5644): [STC::queueBuffer] (this:0x51247728) fps:3.00, dur:1001.27, max:782.15, min:67.85
04-06 11:45:46.464: D/AbsListView(5644): checkAbsListViewlLogProperty get invalid command
04-06 11:45:46.468: D/dalvikvm(5644): create interp thread : stack size=32KB
04-06 11:45:46.468: D/dalvikvm(5644): create new thread
04-06 11:45:46.469: D/dalvikvm(5644): new thread created
04-06 11:45:46.469: D/dalvikvm(5644): update thread list
04-06 11:45:46.469: D/dalvikvm(5644): threadid=13: interp stack at 0x51cc3000
04-06 11:45:46.469: D/dalvikvm(5644): threadid=13: created from interp
04-06 11:45:46.469: D/dalvikvm(5644): start new thread
04-06 11:45:46.470: D/dalvikvm(5644): threadid=13: notify debugger
04-06 11:45:46.470: D/dalvikvm(5644): threadid=13 (Timer-0): calling run()
04-06 11:45:46.470: D/dalvikvm(5644): threadid=13: exiting
04-06 11:45:46.471: W/dalvikvm(5644): threadid=13: thread exiting with uncaught exception (group=0x40f1e908)
04-06 11:45:46.473: E/AndroidRuntime(5644): FATAL EXCEPTION: Timer-0
04-06 11:45:46.473: E/AndroidRuntime(5644): java.lang.RuntimeException: Can't create handler inside thread that has not called Looper.prepare()
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.os.Handler.<init>(Handler.java:121)
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.app.Dialog.<init>(Dialog.java:107)
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.app.AlertDialog.<init>(AlertDialog.java:114)
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.app.AlertDialog.<init>(AlertDialog.java:98)
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.app.ProgressDialog.<init>(ProgressDialog.java:77)
04-06 11:45:46.473: E/AndroidRuntime(5644): at com.example.groupchat.MsgViewActivity$GetMsgs.onPreExecute(MsgViewActivity.java:100)
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.os.AsyncTask.executeOnExecutor(AsyncTask.java:586)
04-06 11:45:46.473: E/AndroidRuntime(5644): at android.os.AsyncTask.execute(AsyncTask.java:534)
04-06 11:45:46.473: E/AndroidRuntime(5644): at com.example.groupchat.MsgViewActivity$1.run(MsgViewActivity.java:57)
04-06 11:45:46.473: E/AndroidRuntime(5644): at java.util.Timer$TimerImpl.run(Timer.java:284)
04-06 11:45:46.482: V/InputMethodManager(5644): focusOut: android.widget.ListView@41c2fd98 mServedView=android.widget.ListView@41c2fd98 winFocus=false
04-06 11:45:46.493: V/InputMethodManager(5644): Not IME target window, ignoring
04-06 11:45:46.675: D/OpenGLRenderer(5644): Flushing caches (mode 0)
04-06 11:45:46.838: D/OpenGLRenderer(5644): Flushing caches (mode 0)
04-06 11:45:48.058: D/OpenGLRenderer(5644): Flushing caches (mode 0)
04-06 11:45:48.071: D/OpenGLRenderer(5644): Flushing caches (mode 0)
04-06 11:45:48.074: D/OpenGLRenderer(5644): Flushing caches (mode 1)
工作代码：
public void callAsynchronousTask() {
final Handler handler = new Handler();
Timer timer = new Timer();
TimerTask doAsynchronousTask = new TimerTask() {
@Override
public void run() {
handler.post(new Runnable() {
public void run() {
try {
GetMsgs performBackgroundTask = new GetMsgs();
// PerformBackgroundTask this class is the class that extends AsynchTask
performBackgroundTask.execute();
} catch (Exception e) {
// TODO Auto-generated catch block
}
}
});
}
};
timer.schedule(doAsynchronousTask, 0, 1000*10); //execute in every 50000 ms
}
答案 0 :(得分：4)
重要的删除代码
new GetMsgs().execute();
从Timer中启动并在您的活动的onCreate方法中启动它，并在您的活动的Destroy方法中停止您的异步任务
class GetMsgs extends AsyncTask<String, String, String> {
boolean flag = false;
@Override
protected void onPreExecute() {
super.onPreExecute();
flag = true;
}
@Override
protected String doInBackground(String... arg0) {
while(flag)
{
publishProgress("start");
//Your Code what you are doing in the Do inBackground
try
{
Thread.sleep(3000);//Your Interval after which you want to refresh the screen
}
catch (InterruptedException e)
{
}
publishProgress("stop");
}
return null;
}
@Override
protected void onProgressUpdate(String... values)
{
super.onProgressUpdate(values);
if(values[0].equalsIgnoreCase("start"))
{
//Create Your Dialog in it
//Do here what you are doing in the onPreExecute
}
else if(values[0].equalsIgnoreCase("stop"))
{
//Code you are doing in the onPostExecute
}
}
@Override
protected void onCancelled() {
// TODO Auto-generated method stub
super.onCancelled();
flag = false;
}
}
答案 1 :(得分：0)
如果以特定间隔运行代码，您可以使用AlarmManager在需要时运行。您可以使用setRepeating()按指定的时间间隔运行它。
This answer gives a small snippet on starting with AlarmManager你可以在SO上找到很多关于它的帖子。