我有一个相当简单的JavaFX GUI应用程序,它有一个标签,显示在某个操作开始之前还有多少时间。为了实现这一点,我创建了一个DownloadTimer类,如下所示:
public class DownloadTimer(){
private int minutes;
private int seconds;
private Timer innerTimer = new Timer();
private TimerTask innerTask;
private boolean isActive;
public DownloadTimer(int minutes, int seconds) {
if (seconds > 60) {
int minToAdd = seconds / 60;
this.minutes = minutes;
this.minutes += minToAdd;
this.seconds = seconds % 60;
} else {
this.minutes = minutes;
this.seconds = seconds;
}
}
public void start() {
innerTask = new TimerTask() {
@Override
public void run() {
isActive = true;
System.out.println(getTime());
if (seconds == 0 && minutes > 0){
minutes -= 1;
seconds = 59;
} else if (seconds == 0 && minutes == 0){
isActive = false;
innerTimer.cancel();
innerTimer.purge();
System.out.println("DownloadTimer DONE");
} else {
seconds -= 1;
}
}
};
innerTimer.scheduleAtFixedRate(innerTask, 0, 1000);
}
}
然后,我创建DownloadTimer对象,并从我的Main(JavaFX)类开始倒计时:
/*
code omitted for better readability
*/
downloadTimer = new DownloadTimer(0, 5);
// label gets the .getTime() value, which returns a formatted String like "00:05", "00:04", etc.
lblTimer.setText( downloadTimer.getTime() );
// start the countdown
downloadTimer.start();
// create a new timer which checks if the downloadTimer is still counting
final Timer timer = new Timer();
TimerTask timerTask = new TimerTask(){
@Override
public void run(){
if (downloadTimer.getIsActive() == false){
timer.cancel();
timer.purge();
System.out.println("GUI timer DONE");
} else {
// if it's still running, then continuously update the label's text
lblTimer.setText( downloadTimer.getTime() );
// this is where I get the error described below
}
}
};
// repeat after 1000ms
timer.scheduleAtFixedRate(timerTask, 0, 1000);
我遇到的问题是,我无法从Main类中使用lblTimer.setText( downloadTimer.getTime() );
设置标签文本,并且我得到的错误是TimerThread.run() line: not available [local variables unavailable]
,如图所示。
我读过关于ScheduledThreadPoolExecutor和Java Timer与ExecutorService的文章,但我很好奇这是否可以使用两个单独的Timer和TimerTasks来完成。如有任何帮助和/或提示,我们将不胜感激。
我很惊讶你没有看到异常。要从单独的线程更新标签,需要安排在FX线程中运行更新:
Platform.runLater(new Runnable() {
public void run() {
lblTimer.setText(downloadTimer.getTime());
}
});