android - 重新安排。取消后的计时器给出 "java.lang.IllegalStateException: Timer cancelled."

Question

我想知道取消后是否可以重新安排计时器。这里说，http://www.coderanch.com/t/452066/java/java/Exception-timer-IllegalStateException ，一旦你取消了定时器，就不可能在同一个定时器上安排任何事情，除非我创建一个新的定时器。而且，我遇到了以下错误，java.lang.IllegalStateException: Timer was cancelled.我正在尝试推出一个可以定期执行 Wifi 扫描的计时器。但是我希望“暂停”或者如果不是，则在扫描后执行某些计算时取消计时器。只有在它完成计算并返回一些结果后，我才会恢复计时器。谁能告诉我如何着手解决这个问题？

忘记提到只有在我使用 AsyncTask 完成图像加载后我才会启动计时器。

我试图在一个单独的线程中实现这一点，这样它就不会占用 UI 线程。

这是程序的粗略框架和启动计时器，只有在图像完全加载后(在“load.execute(context);"):

public class LargeImageScroller extends Activity {
@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
        setContentView(new SampleView(this));
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {...}

@Override
public boolean onOptionsItemSelected(MenuItem item) {...}

//this is the class where the program would do all the UI and display images
private static class SampleView extends View {

    public SampleView(Context context) {
                    :
        loadMap load = new loadMap();
        load.execute(context);

        scanTask = new TimerTask(){

            @Override
            public void run() {
                // TODO Auto-generated method stub
               handler.post(new Runnable() {
                        public void run() {
                         wifi = (WifiManager)context.getSystemService(WIFI_SERVICE);
                         context.registerReceiver(receiverWifi, new IntentFilter(WifiManager.SCAN_RESULTS_AVAILABLE_ACTION));
                         wifi.startScan();
                         Log.d("TIMER", "Timer set off");
                        }
               });
            }

        };

        scanTimer.schedule(scanTask, refreshRate);
    }

    public class wifiReceiver extends BroadcastReceiver{

        @Override
        public void onReceive(Context context, Intent intent) {
            // TODO Auto-generated method stub
            List<ScanResult> sc = wifi.getScanResults(); 
            for(int i=0; i<sc.size(); i++){
                Log.e("AndroidRuntime", sc.get(i).SSID);
            }
        }

    }
    public boolean onTouchEvent(MotionEvent event) {...}
    protected void onDraw(Canvas canvas) {...}
    private static Drawable LoadImageFromWebOperations(String url){...}
    private static Bitmap decodeFile(File f, int requiredSize){...}
    private class loadMap extends AsyncTask<Context, Void, ArrayList<Bitmap>>{...}
}

使用包含的权限:

<uses-permission android:name="android.permission.ACCESS_WIFI_STATE" />
<uses-permission android:name="android.permission.CHANGE_WIFI_STATE"></uses-permission>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"></uses-permission>
<uses-permission android:name="android.permission.DELETE_CACHE_FILES"></uses-permission>
<uses-permission android:name="android.permission.INTERNET"></uses-permission>

广播接收器遇到的错误:

10-25 05:53:04.903: ERROR/ActivityThread(1551): Activity android.wps.LargeImageScroller has leaked IntentReceiver android.wps.LargeImageScroller$SampleView$wifiReceiver@43d1bca0 that was originally registered here. Are you missing a call to unregisterReceiver()?
10-25 05:53:04.903: ERROR/ActivityThread(1551): android.app.IntentReceiverLeaked: Activity android.wps.LargeImageScroller has leaked IntentReceiver android.wps.LargeImageScroller$SampleView$wifiReceiver@43d1bca0 that was originally registered here. Are you missing a call to unregisterReceiver()?
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.app.ActivityThread$PackageInfo$ReceiverDispatcher.<init>(ActivityThread.java:797)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.app.ActivityThread$PackageInfo.getReceiverDispatcher(ActivityThread.java:608)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.app.ApplicationContext.registerReceiverInternal(ApplicationContext.java:724)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.app.ApplicationContext.registerReceiver(ApplicationContext.java:711)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.app.ApplicationContext.registerReceiver(ApplicationContext.java:705)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.content.ContextWrapper.registerReceiver(ContextWrapper.java:308)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.wps.LargeImageScroller$SampleView$1$1.run(LargeImageScroller.java:187)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.os.Handler.handleCallback(Handler.java:587)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.os.Handler.dispatchMessage(Handler.java:92)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.os.Looper.loop(Looper.java:123)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at android.app.ActivityThread.main(ActivityThread.java:4363)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at java.lang.reflect.Method.invokeNative(Native Method)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at java.lang.reflect.Method.invoke(Method.java:521)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:860)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:618)
10-25 05:53:04.903: ERROR/ActivityThread(1551):     at dalvik.system.NativeStart.main(Native Method)

Answer 1

是的，取消计时器会终止其线程，因此您无法再次使用它。定时器没有任何内置的暂停方法。当你想“暂停”时，你可以取消计时器，当你想“恢复”时，你可以创建一个新的计时器。