错误java.lang.IndexOutOfBoundsException:索引0无效,我的程序android中的大小为0

Question

我开始在android中开发,我尝试修改Snake代码,包括调用浏览器来显示网页,当我执行我的应用程序时它显示在brwser中的页面,但问题是当我回到蛇应用程序时它显示应用程序意外停止的消息,logCat显示下面的例外情况

02-19 01:06:50.920: W/dalvikvm(3394): threadid=1: thread exiting with uncaught exception (group=0x4015a760)
02-19 01:06:50.930: E/AndroidRuntime(3394): FATAL EXCEPTION: main
02-19 01:06:50.930: E/AndroidRuntime(3394): java.lang.IndexOutOfBoundsException: Invalid index 0, size is 0
02-19 01:06:50.930: E/AndroidRuntime(3394):     at java.util.ArrayList.throwIndexOutOfBoundsException(ArrayList.java:255)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at java.util.ArrayList.get(ArrayList.java:308)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.example.android.snake.SnakeView.updateSnake(SnakeView.java:448)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.example.android.snake.SnakeView.update(SnakeView.java:403)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.example.android.snake.SnakeView.setMode(SnakeView.java:335)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.example.android.snake.SnakeView.onKeyDown(SnakeView.java:278)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.KeyEvent.dispatch(KeyEvent.java:2387)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.View.dispatchKeyEvent(View.java:4569)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1113)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1113)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1113)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewGroup.dispatchKeyEvent(ViewGroup.java:1113)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchKeyEvent(PhoneWindow.java:1692)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.android.internal.policy.impl.PhoneWindow.superDispatchKeyEvent(PhoneWindow.java:1260)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.app.Activity.dispatchKeyEvent(Activity.java:2231)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1648)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewRoot.deliverKeyEventPostIme(ViewRoot.java:2730)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewRoot.handleFinishedEvent(ViewRoot.java:2703)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1958)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.os.Handler.dispatchMessage(Handler.java:99)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.os.Looper.loop(Looper.java:126)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at android.app.ActivityThread.main(ActivityThread.java:3997)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at java.lang.reflect.Method.invokeNative(Native Method)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at java.lang.reflect.Method.invoke(Method.java:491)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:841)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:599)
02-19 01:06:50.930: E/AndroidRuntime(3394):     at dalvik.system.NativeStart.main(Native Method)
02-19 01:08:07.450: D/A    

Answer 1

我认为这里很清楚

在com.example.android.snake.SnakeView.updateSnake(SnakeView.java:448)

如果您至少阅读了错误,那么您正在访问ArrayList已被实例化的内容new ArrayList(0),非常简单.

ArrayList 对象意味着自动调整大小,但如果您没有在零大小的数组列表中放置任何内容,则会出现此错误.

Answer 2

你有一个ArrayList0元素.并且在第448行SnakeView的updateSnake()方法中的类中,您尝试访问索引0处的arraylist.索引0是您的第一个元素ArrayList,但如果它是空的,则索引0处没有元素.所以你得到一个IndexOutOfBoundsException