当我启动我的应用程序时，我启动一个AsyncTask来下载。这可能需要一段时间。
当那个线程正在下载数据时，我已经在监听位置更新了。当我收到一个新的位置时，我会启动一个新的AsyncTask来进行一些处理。但是，该类依赖于下载的数据，因此必须等到下载完成：
public void setLocation(Location location) throws IOException {
Logger.log("New location - calculating nearest stations");
if (!initialStationsRead) {
Logger.log("Location update waiting for stations to be read");
while (!initialStationsRead)
;
Logger.log("Location update done waiting");
}
/* Do the processing */
}
第一个线程在完成时将
initialStationsRead设置为true，因此第二个线程可以在完成后拾取。在我的测试设备上一切正常。不过，我收到一个用户的电子邮件，告诉我这个应用程序不会启动。加载屏幕出现，10-12秒后消失，没有任何警告。他用的是宏达电的。
这是他寄给我的那只猫：
07-05 22:11:04.938: W/dalvikvm(19961): threadid=2: spin on suspend #2 threadid=11 (pcf=1)
07-05 22:11:04.938: I/dalvikvm(19961): "GC" daemon prio=5 tid=2 RUNNABLE
07-05 22:11:04.938: I/dalvikvm(19961): | group="system" sCount=0 dsCount=0 obj=0x40d5c580 self=0x1669ae8
07-05 22:11:04.938: I/dalvikvm(19961): | sysTid=19965 nice=0 sched=0/0 cgrp=default handle=21931384
07-05 22:11:04.938: I/dalvikvm(19961): | schedstat=( 0 0 0 ) utm=2 stm=0 core=1
07-05 22:11:04.938: I/dalvikvm(19961): at dalvik.system.NativeStart.run(Native Method)
07-05 22:11:04.938: I/dalvikvm(19961): "AsyncTask #3" prio=5 tid=11 RUNNABLE JIT
07-05 22:11:04.938: I/dalvikvm(19961): | group="main" sCount=1 dsCount=0 obj=0x40f90588 self=0x1b35b00
07-05 22:11:04.938: I/dalvikvm(19961): | sysTid=19991 nice=0 sched=0/0 cgrp=default handle=29193008
07-05 22:11:04.938: I/dalvikvm(19961): | schedstat=( 0 0 0 ) utm=287 stm=1 core=1
07-05 22:11:04.938: I/dalvikvm(19961): at com.busybits.treinverkeer.data.Data.setLocation(Data.java:~102)
07-05 22:11:04.938: I/dalvikvm(19961): at com.busybits.treinverkeer.TreinVerkeer$SetLocationAsyncTask.doInBackground(TreinVerkeer.java:408)
07-05 22:11:04.938: I/dalvikvm(19961): at com.busybits.treinverkeer.TreinVerkeer$SetLocationAsyncTask.doInBackground(TreinVerkeer.java:1)
07-05 22:11:04.938: I/dalvikvm(19961): at android.os.AsyncTask$2.call(AsyncTask.java:264)
07-05 22:11:04.938: I/dalvikvm(19961): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-05 22:11:04.938: I/dalvikvm(19961): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-05 22:11:04.938: I/dalvikvm(19961): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
07-05 22:11:04.938: I/dalvikvm(19961): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
07-05 22:11:04.938: I/dalvikvm(19961): at java.lang.Thread.run(Thread.java:864)
07-05 22:11:05.629: D/WifiStateMachine(436): fetchRssiAndLinkSpeedNative RSSI = -32
07-05 22:11:05.689: W/dalvikvm(19961): threadid=2: spin on suspend #3 threadid=11 (pcf=1)
07-05 22:11:05.689: I/dalvikvm(19961): "GC" daemon prio=5 tid=2 RUNNABLE
07-05 22:11:05.689: I/dalvikvm(19961): | group="system" sCount=0 dsCount=0 obj=0x40d5c580 self=0x1669ae8
07-05 22:11:05.689: I/dalvikvm(19961): | sysTid=19965 nice=0 sched=0/0 cgrp=default handle=21931384
07-05 22:11:05.689: I/dalvikvm(19961): | schedstat=( 0 0 0 ) utm=2 stm=0 core=1
07-05 22:11:05.689: I/dalvikvm(19961): at dalvik.system.NativeStart.run(Native Method)
07-05 22:11:05.689: I/dalvikvm(19961): "AsyncTask #3" prio=5 tid=11 RUNNABLE JIT
07-05 22:11:05.689: I/dalvikvm(19961): | group="main" sCount=1 dsCount=0 obj=0x40f90588 self=0x1b35b00
07-05 22:11:05.689: I/dalvikvm(19961): | sysTid=19991 nice=0 sched=0/0 cgrp=default handle=29193008
07-05 22:11:05.689: I/dalvikvm(19961): | schedstat=( 0 0 0 ) utm=362 stm=1 core=1
07-05 22:11:05.689: I/dalvikvm(19961): at com.busybits.treinverkeer.data.Data.setLocation(Data.java:~102)
07-05 22:11:05.689: I/dalvikvm(19961): at com.busybits.treinverkeer.TreinVerkeer$SetLocationAsyncTask.doInBackground(TreinVerkeer.java:408)
07-05 22:11:05.689: I/dalvikvm(19961): at com.busybits.treinverkeer.TreinVerkeer$SetLocationAsyncTask.doInBackground(TreinVerkeer.java:1)
07-05 22:11:05.689: I/dalvikvm(19961): at android.os.AsyncTask$2.call(AsyncTask.java:264)
07-05 22:11:05.689: I/dalvikvm(19961): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-05 22:11:05.689: I/dalvikvm(19961): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-05 22:11:05.689: I/dalvikvm(19961): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
07-05 22:11:05.689: I/dalvikvm(19961): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
07-05 22:11:05.689: I/dalvikvm(19961): at java.lang.Thread.run(Thread.java:864)
07-05 22:11:05.719: D/skia(1004): AndroidImageRef[ 0x2438190 ] releasePixel fail as lockCount=1
07-05 22:11:06.439: W/dalvikvm(19961): threadid=2: spin on suspend #4 threadid=11 (pcf=1)
07-05 22:11:06.439: I/dalvikvm(19961): "GC" daemon prio=5 tid=2 RUNNABLE
07-05 22:11:06.439: I/dalvikvm(19961): | group="system" sCount=0 dsCount=0 obj=0x40d5c580 self=0x1669ae8
07-05 22:11:06.439: I/dalvikvm(19961): | sysTid=19965 nice=0 sched=0/0 cgrp=default handle=21931384
07-05 22:11:06.439: I/dalvikvm(19961): | schedstat=( 0 0 0 ) utm=2 stm=0 core=1
07-05 22:11:06.439: I/dalvikvm(19961): at dalvik.system.NativeStart.run(Native Method)
07-05 22:11:06.439: I/dalvikvm(19961): "AsyncTask #3" prio=5 tid=11 RUNNABLE JIT
07-05 22:11:06.439: I/dalvikvm(19961): | group="main" sCount=1 dsCount=0 obj=0x40f90588 self=0x1b35b00
07-05 22:11:06.439: I/dalvikvm(19961): | sysTid=19991 nice=0 sched=0/0 cgrp=default handle=29193008
07-05 22:11:06.439: I/dalvikvm(19961): | schedstat=( 0 0 0 ) utm=437 stm=1 core=1
07-05 22:11:06.439: I/dalvikvm(19961): at com.busybits.treinverkeer.data.Data.setLocation(Data.java:~102)
07-05 22:11:06.439: I/dalvikvm(19961): at com.busybits.treinverkeer.TreinVerkeer$SetLocationAsyncTask.doInBackground(TreinVerkeer.java:408)
07-05 22:11:06.439: I/dalvikvm(19961): at com.busybits.treinverkeer.TreinVerkeer$SetLocationAsyncTask.doInBackground(TreinVerkeer.java:1)
07-05 22:11:06.439: I/dalvikvm(19961): at android.os.AsyncTask$2.call(AsyncTask.java:264)
07-05 22:11:06.439: I/dalvikvm(19961): at java.util.concurrent.FutureTask$Sync.innerRun(FutureTask.java:305)
07-05 22:11:06.439: I/dalvikvm(19961): at java.util.concurrent.FutureTask.run(FutureTask.java:137)
07-05 22:11:06.439: I/dalvikvm(19961): at java.util.concurrent.ThreadPoolExecutor.runWorker(ThreadPoolExecutor.java:1076)
07-05 22:11:06.439: I/dalvikvm(19961): at java.util.concurrent.ThreadPoolExecutor$Worker.run(ThreadPoolExecutor.java:569)
07-05 22:11:06.439: I/dalvikvm(19961): at java.lang.Thread.run(Thread.java:864)
重复X次。
现在，
Data.java:102是行，所以肯定出了问题。发生了什么，我该怎么解决？
最佳答案
第一个线程在完成时将initialstationsread设置为true，这样第二个线程就可以在完成后进行拾取。
繁忙的循环是邪恶的化身。如果我手边有圣水的话，你现在会很湿的。-）
（这也意味着我有很好的圣水远射目标，但事实并非如此）
Java有很多线程同步的选项，并且已经有十年了，从低级wait()和notify() on Object到java.util.concurrent构造，如Semaphore。选一个，用它，摆脱繁忙的循环。
或者，按照jan henk的建议，基于一个标志，在同一个线程上连续地执行该工作。
你知道为什么这会发生在他的设备上，而不是我的或其他我认识的人的设备上吗？
好吧，首先，一个s是双核的，所以你的线程可能同时运行（每个核一个）。在多核环境中，线程问题更容易出现。
另外，安吉洛的回答——我写这篇文章的时候贴出来的——也值得注意。