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我正在开发针对Android 2.2+的简单视频录制应用程序，并且无法按预期方式使Timer线程正常工作。代码如下，所以步骤如下：在Java中使用通知/等待来停止/重新启动线程
- 当用户pres开始录制按钮时，开始录制并调用fightTimer.start（）方法。
- 它调用timer.start（）方法开始运行线程。定时器是fightTimer内部的线程对象
- 当用户单击停止按钮时，调用stopTimer方法stop（）。在那里，我设置了一个标志stopTimer = true，并停止线程方法运行并调用timer.wait（）方法，以便线程在用户单击开始录制按钮时等待
- 然后再次调用fightTimer.start（）方法。它调用线程timer.start（），因为计时器已经启动，但是它会抛出异常。
- 我发现异常并调用fightTimer.restart（）方法。此方法设置标志stopTimer我在步骤3中设置为true，所以现在我们有stopTimer = true。计时器线程仍在运行的内等待（）方法
- 然后调用timer.notify（），让定时器知道，它不需要等待了，可以继续运行
- 现在我期待的计时器线程启动再次运行，但由于某种原因，此时执行跳转到调用notify（）（restart（））的同一方法的开头，并设置标志stopTimer = false，然后尝试再次通知定时器线程。它引发运行时异常，并且它是结束的地方。
我认为我对线程的整体同步的理解是不正确的，所以如果任何人都能指出我搞砸的地方那会很好。下面是FightTimeris的代码，我甚至没有在logCat中获得任何输出信息。就像我说的任何帮助将不胜感激，因为我不明白为什么会发生这种情况，以及如何解决它。
public class FightTimer extends SurfaceView implements Runnable, SurfaceHolder.Callback {
public Thread timer;
public SurfaceHolder surfaceHolder;
public Canvas canvas;
public int counter=0;
public volatile boolean stopTimer=false;
public volatile boolean pauseTimer=false;
public FightTimer(Context context)
{
super(context);
surfaceHolder=getHolder();
// this is necessary to make surfaceview transparent
surfaceHolder.setFormat(PixelFormat.TRANSLUCENT);
setZOrderOnTop(true);
surfaceHolder.addCallback(this);
timer=new Thread(this);
}
public void start()
{
try
{
timer.start();
}
catch(IllegalThreadStateException ex)
{
reStart();
}
}
public synchronized void reStart()
{
// here the method is executed twice as I described in step 7
// after notify() it actually jumps back to stopTimer=false again and then exits the function. Then outside of this object I catch RuntimeException
stopTimer=false;
timer.notify();
}
public synchronized void pause()
{
pauseTimer=true;
}
public synchronized void resume()
{
pauseTimer=false;
timer.notify();
}
public void stop()
{
stopTimer=true;
}
public void run() {
TimeWatch timeWatch=TimeWatch.start();
Paint paint=new Paint();
paint.setColor(Color.RED);
paint.setTypeface(Typeface.create("Arial",Typeface.NORMAL));
paint.setTextSize(20);
while(true)
{
// this is to pause timer
try
{
if(pauseTimer)
{
synchronized(timer) {
while(pauseTimer)
timer.wait();
}
// TODO heres the code should be executed when timer is resumed eg.
// maybe calculate how timer should count now as it wasn't counting for a while etc
}
} catch(InterruptedException ex)
{
}
// this is to pause timer
try
{
if(stopTimer)
{
synchronized(timer) {
while(stopTimer)
timer.wait();
}
// TODO heres the code should be executed when timer is restarted
// maybe reset timer completely etc
timeWatch.reset();
}
} catch(InterruptedException ex)
{
}
canvas=surfaceHolder.lockCanvas();
// canvas might not exists at this point as we might be in activitis onStop() callback and stopping preview
// etc. so we need to check if so then we exit run function
if(canvas==null) return;
//canvas.drawARGB(0,255,255,255);
canvas.drawColor(0, android.graphics.PorterDuff.Mode.CLEAR);
long minutes=timeWatch.time(TimeUnit.SECONDS)/60;
canvas.drawText(counter+" "+minutes+":"+timeWatch.time(TimeUnit.SECONDS)%60,0,counter%60, paint);
counter++;
surfaceHolder.unlockCanvasAndPost(canvas);
}
}
public void surfaceChanged(SurfaceHolder holder, int format, int width,
int height) {
// TODO Auto-generated method stub
//Toast.makeText(getContext(), "Surface Changed", Toast.LENGTH_LONG).show();
}
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
//timer.start();
}
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
// when surface is destroyed it means it cannot be displayed anymore and there is no canvas to draw
// meaning the run() method cannot draw anything and calls to surfaceHolder will throw exception
// so we need to stop thread here
// this will happen when activity is in onStop() callback and when is already invisible and we are going to
// remove the object anyway so we don't care what will happenn later and make it wait. All we need is stop
// run() from calling any other methods on canvas from surfaceHolder
Toast.makeText(getContext(), "Surface Destroyed", Toast.LENGTH_LONG).show();
}
public void setSurfaceHolder(SurfaceHolder surfaceHolder2) {
// TODO Auto-generated method stub
surfaceHolder=surfaceHolder2;
}
}
另请参阅在重新启动（）方法中编辑的注释。当重新启动（）方法退出时，以下是调用堆栈。请让我知道是否需要更多信息。
DalvikVM[localhost:8754]
Thread [<1> main] (Suspended)
<VM does not provide monitor information>
MyFirstAppActivity.startRecording(View) line: 271
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]
Method.invoke(Object, Object...) line: 521
View$1.onClick(View) line: 2077
Button(View).performClick() line: 2461
View$PerformClick.run() line: 8888
ViewRoot(Handler).handleCallback(Message) line: 587
ViewRoot(Handler).dispatchMessage(Message) line: 92
Looper.loop() line: 123
ActivityThread.main(String[]) line: 4627
Method.invokeNative(Object, Object[], Class, Class[], Class, int, boolean) line: not available [native method]
Method.invoke(Object, Object...) line: 521
ZygoteInit$MethodAndArgsCaller.run() line: 858
ZygoteInit.main(String[]) line: 616
NativeStart.main(String[]) line: not available [native method]
Thread [<7> Binder Thread #2] (Running)
Thread [<6> Binder Thread #1] (Running)
Thread [<8> Binder Thread #3] (Running)
Thread [<9> Thread-9] (Running)
发布从Eclipse的调试窗口发布的异常调用堆栈 – nandeesh 2012-08-17 01:24:04
。它有帮助还是我应该提供更多信息？ – spirytus 2012-08-17 01:40:35