为超时设置计时器-取消和清除后，new Timer()将失败

Question

我有一些位置查找代码，在等待适当精度的读取时，我也想暂停并使用到目前为止的最佳位置读取。

我似乎误解了如何取消和重新启动计时器。

我想在开始搜索时启动超时计时器，并在每次重复搜索时重新启动计时器。。。

private void refreshLocation() {
    if (locationTimeoutTimer != null) {
        locationTimeoutTimer.cancel();
        locationTimeoutTimer.purge();
    }
    locationTimeoutTimer = new Timer();
    locationTimeoutTimer.schedule(timeoutReached, 60000);
        //Do other things...
}

然而，每当第二次调用这个refreshLocation时，我都会收到以下错误。

java.lang.IllegalStateException: TimerTask is scheduled already

Answer 1

您的代码与我的代码非常相似，正在运行。但我注意到的一些差异是

• 您可能需要将新计时器创建为命名守护进程，例如locationTimer = new Timer("locationtimer", true);
• 您可能需要在每次计划时创建一个新的TimerTask（我假设timeoutReached是TimerTask？），例如locationTimer.schedule(new timeoutReached(), 60000);

Answer 2

计时器在UI上无法正常工作。从不使用处理程序。你也可以参加我的课程：它启动/停止计时，并在注册的TextView字段中显示时间和/或日期。

import java.text.SimpleDateFormat;
import java.util.ArrayList;
import java.util.Date;
import android.os.Handler;
import android.widget.TextView;
/**
 * The class for creating and refreshing many different fields on different layouts,
 * that can hold actual time and/or date in different formats 
 * The formats should be as in http://developer.android.com/reference/java/text/SimpleDateFormat.html. 
 * Only present and visible fields are being actualized, so there is no need to clean the clock list after closing an activity
 * 
 * Examples of use:
 * 
 *      Clock.registerClock((TextView) findViewById(R.id.TimeField), "HH:mm");
 *      Clock.registerClock((TextView) findViewById(R.id.DateField), "d.M.yyyy EEE");
 *      Clock.start(10000L);
 *
 * @author Petr Gangnus
 */
public final class Clock {
    /**
     * the handler that works instead of timer and supports UI
     */
    static private Handler handler = new Handler();
    /**
     * the interval of the time refreshing
     */
    static private long refreshStep;
    /**
     * pairs TextView timer+time/date format
     */
    private TextView clockFace;
    private String format;
    private Clock(TextView clockFace, String format){
        this.clockFace=clockFace;
        this.format=format;
    }
    // here is the list of views containing the visual timers that should be held actual
    static private ArrayList<Clock> clocks=new ArrayList<Clock>();
    /**
     * fills all timer fields by actual time value, according to their formats.
     */
    static private Runnable mUpdateTimeTask = new Runnable() {
       public void run() {
           for(Clock clock:clocks){
               showActualTimeDate(clock);
           }
           handler.postDelayed(this,refreshStep);
       }
    };
    //============================================ public members ====================================================================
    /**
     * add a clock to the list of updating clocks
     * @param clockFace - the place where the time or date will be shown 
     * @param format - the format of the time/date 
     * @return
     */
    public static boolean registerClock(TextView clockFace, String format){
        if (clockFace==null) return false;
        if(clocks.contains(clockFace)){
            // old clockFace
            clocks.get(clocks.indexOf(clockFace)).format=format;
        } else {
            // new clockFace
            clocks.add(new Clock(clockFace, format));
        }
        return true;
    }
    /**
     * remove a clock from the updating list
     * @param clockFace
     * @return
     */
    public static boolean unRegisterClock(TextView clockFace){
        if (clockFace==null) return false;
        if(clocks.contains(clockFace)){
            // found clockFace
            clocks.remove(clocks.indexOf(clockFace));
        } else {
            // not found clockFace
            return false;
        }
        return true;
    }
    /**
     * put in the "place" the actual date/time in the appropriate "format"
     * @param place
     * @param format
     */
    public static void showActualTimeDate(Clock clock){
        if (clock.clockFace==null) return;
        if (clock.clockFace.getVisibility()!=TextView.VISIBLE) return;
        Date thisDate=new Date();
        SimpleDateFormat df=new SimpleDateFormat(clock.format);
        clock.clockFace.setText(df.format(thisDate));
    }
    /**
     * start the ticking for all clocks
     * @param step the tick interval
     */
    public static void start(long step) { 
        refreshStep=step;
        handler.removeCallbacks(mUpdateTimeTask);
        handler.postDelayed(mUpdateTimeTask, 0);
    }
    /**
     * Stopping ticking all clocks (not removing them)
     * the calling could be put somewhere in onStop
     */
    public static void stop() { 
        handler.removeCallbacks(mUpdateTimeTask);
    }
}