我有这个简单的 Activity (在 Scala 中,省略了导入):
class TestActivity extends Activity {
private val TAG = "TestActivity"
private val mHandler = new Handler {
override def handleMessage(msg: Message) {
Log.d(TAG, "handleMessage")
}
}
private val mThread = new Thread {
override def run {
mHandler.sendEmptyMessage(0)
Thread.sleep(10)
run
}
}.start
override def onCreate(savedInstanceState: Bundle) {
super.onCreate(savedInstanceState)
setContentView(new TextView(this) {
setText("hello, world")
})
}
}
如您所见,mThread
立即启动,run
被尾递归覆盖,它向 mHandler
发送空消息, hibernate 短时间并再次发送相同的消息。 Activity 开始时,出现此错误:
....
D/TestActivity(28224): handleMessage
D/TestActivity(28224): handleMessage
D/TestActivity(28224): handleMessage
D/TestActivity(28224): handleMessage
I/dalvikvm(28224): threadid=9: stack overflow on call to Landroid/os/MessageQueue;.nativeWake:VI
I/dalvikvm(28224): method requires 8+20+0=28 bytes, fp is 0x43e33310 (16 left)
I/dalvikvm(28224): expanding stack end (0x43e33300 to 0x43e33000)
I/dalvikvm(28224): Shrank stack (to 0x43e33300, curFrame is 0x43e35fe0)
W/dalvikvm(28224): threadid=9: thread exiting with uncaught exception (group=0x40015560)
E/AndroidRuntime(28224): FATAL EXCEPTION: Thread-10
E/AndroidRuntime(28224): java.lang.StackOverflowError
E/AndroidRuntime(28224): at android.os.MessageQueue.enqueueMessage(MessageQueue.java:223)
E/AndroidRuntime(28224): at android.os.Handler.sendMessageAtTime(Handler.java:457)
E/AndroidRuntime(28224): at android.os.Handler.sendMessageDelayed(Handler.java:430)
E/AndroidRuntime(28224): at android.os.Handler.sendEmptyMessageDelayed(Handler.java:394)
E/AndroidRuntime(28224): at android.os.Handler.sendEmptyMessage(Handler.java:379)
E/AndroidRuntime(28224): at com.iped.audiotest.MainActivity$$anon$2.run(Activity.scala:20)
E/AndroidRuntime(28224): at com.iped.audiotest.MainActivity$$anon$2.run(Activity.scala:22)
E/AndroidRuntime(28224): at com.iped.audiotest.MainActivity$$anon$2.run(Activity.scala:22)
E/AndroidRuntime(28224): at com.iped.audiotest.MainActivity$$anon$2.run(Activity.scala:22)
...
现在,如果我不在 mThread
创建后立即启动它,就像这样:
private val mThread = new Thread {
override def run {
mHandler.sendEmptyMessage(0)
Thread.sleep(10)
run
}
}
并在其他地方触发它,例如,在触摸事件上:
override def onTouchEvent(event: MotionEvent): Boolean = {
if (event.getAction == MotionEvent.ACTION_DOWN)
mThread.start
true
}
一切都会好起来的。
我无法解释这个。
最佳答案
所以我做了一些实验,我必须得出结论,如果尾递归覆盖 run
的 Thread 在其创建时的相同表达式中启动,则尾调用优化将失败(还是其他任何可能导致错误的原因?)
差:
class Test {
val mThread = new Thread {
override def run {
println("hello")
run
}
}.start
}
好:
class Test {
val mThread = new Thread {
override def run {
println("hello")
run
}
}
mThread.start
}
附言我正在运行 Scala 2.9.1,但由于库较小,我使用 2.8.2 进行 Android 开发。
关于java - Android(在 Scala 中): StackOverflowError depends on when to start a thread?,我们在Stack Overflow上找到一个类似的问题: https://stackoverflow.com/questions/7884482/