定义为 static function1(), function1() 中不能引用this或super.
在android 中这样用的话,会出现以下的报错
W/dalvikvm( 2783): JNI WARNING: instance fieldID 0x57ee6ab8 not valid for class Ljava/lang/Class;
W/dalvikvm( 2783): in Lcom/tcl/media/TMediaPlayer;._setAudioTrack:(I)V (GetIntField)
I/dalvikvm( 2783): "main" prio=5 tid=1 RUNNABLE
I/dalvikvm( 2783): | group="main" sCount=0 dsCount=0 obj=0x41e3f578 self=0x41e2a738
I/dalvikvm( 2783): | sysTid=2783 nice=0 sched=0/0 cgrp=apps handle=1074913276
I/dalvikvm( 2783): | state=R schedstat=( 2625678561 263517020 5312 ) utm=176 stm=85 core=1
I/dalvikvm( 2783): at com.tcl.media.TMediaPlayer._setAudioTrack(Native Method)
I/dalvikvm( 2783): at com.tcl.media.TMediaPlayer.setAudioTrack(TMediaPlayer.java:186)
I/dalvikvm( 2783): at com.tcl.common.mediaplayer.video.contrl.IVideoPlayControlHandler.setAudioTrackNms(IVideoPlayControlHandler.java:1007)
I/dalvikvm( 2783): at com.tcl.common.mediaplayer.video.UI.VideoAdvanceDialogActivity.onKeyDown(VideoAdvanceDialogActivity.java:117)
I/dalvikvm( 2783): at android.view.KeyEvent.dispatch(KeyEvent.java:2960)
I/dalvikvm( 2783): at android.app.Activity.dispatchKeyEvent(Activity.java:2389)
I/dalvikvm( 2783): at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchKeyEvent(PhoneWindow.java:1861)
I/dalvikvm( 2783): at android.view.ViewRootImpl$ViewPostImeInputStage.processKeyEvent(ViewRootImpl.java:3832)
I/dalvikvm( 2783): at android.view.ViewRootImpl$ViewPostImeInputStage.onProcess(ViewRootImpl.java:3815)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3420)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3470)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3439)
I/dalvikvm( 2783): at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3524)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3447)
I/dalvikvm( 2783): at android.view.ViewRootImpl$AsyncInputStage.apply(ViewRootImpl.java:3581)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3420)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3470)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3439)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.apply(ViewRootImpl.java:3447)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.deliver(ViewRootImpl.java:3420)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.onDeliverToNext(ViewRootImpl.java:3470)
I/dalvikvm( 2783): at android.view.ViewRootImpl$InputStage.forward(ViewRootImpl.java:3439)
I/dalvikvm( 2783): at android.view.ViewRootImpl$AsyncInputStage.forward(ViewRootImpl.java:3557)
I/dalvikvm( 2783): at android.view.ViewRootImpl$ImeInputStage.onFinishedInputEvent(ViewRootImpl.java:3707)
I/dalvikvm( 2783): at android.view.inputmethod.InputMethodManager$PendingEvent.run(InputMethodManager.java:1982)
I/dalvikvm( 2783): at android.view.inputmethod.InputMethodManager.invokeFinishedInputEventCallback(InputMethodManager.java:1698)
I/dalvikvm( 2783): at android.view.inputmethod.InputMethodManager.finishedInputEvent(InputMethodManager.java:1689)
I/dalvikvm( 2783): at android.view.inputmethod.InputMethodManager$ImeInputEventSender.onInputEventFinished(InputMethodManager.java:1959)
I/dalvikvm( 2783): at android.view.InputEventSender.dispatchInputEventFinished(InputEventSender.java:141)
I/dalvikvm( 2783): at android.os.MessageQueue.nativePollOnce(Native Method)
I/dalvikvm( 2783): at android.os.MessageQueue.next(MessageQueue.java:132)
I/dalvikvm( 2783): at android.os.Looper.loop(Looper.java:124)
I/dalvikvm( 2783): at android.app.ActivityThread.main(ActivityThread.java:5103)
I/dalvikvm( 2783): at java.lang.reflect.Method.invokeNative(Native Method)
I/dalvikvm( 2783): at java.lang.reflect.Method.invoke(Method.java:525)
I/dalvikvm( 2783): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:773)
I/dalvikvm( 2783): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:589)
I/dalvikvm( 2783): at dalvik.system.NativeStart.main(Native Method)
I/dalvikvm( 2783):
E/dalvikvm( 2783): VM aborting
以下转自:http://developer.51cto.com/art/200611/35011.htm
Java中static的作用
如果一个成员被声明为static,它就能够在它的类的任何对象创建之前被访问,而不必引用任何对象。你可以将方法和变量都声明为static。static 成员的最常见的例子是main( ) 。因为在程序开始执行时必须调用main() ,所以它被声明为static。
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有时你希望定义一个类成员,使它的使用完全独立于该类的任何对象。通常情况下,类成员必须通过它的类的对象访问,但是可以创建这样一个成员,它能够被它自己使用,而不必引用特定的实例。在成员的声明前面加上关键字static(静态的)就能创建这样的成员。如果一个成员被声明为static,它就能够在它的类的任何对象创建之前被访问,而不必引用任何对象。你可以将方法和变量都声明为static。static 成员的最常见的例子是main( ) 。因为在程序开始执行时必须调用main() ,所以它被声明为static。
声明为static的变量实质上就是全局变量。当声明一个对象时,并不产生static变量的拷贝,而是该类所有的实例变量共用同一个static变量。声明为static的方法有以下几条限制:
◆它们仅能调用其他的static 方法。
◆它们只能访问static数据。
◆它们不能以任何方式引用this 或super
package com.birdme; public class UseStatic { /** * @param args */ private static int s; public UseStatic(){ System.out.println("Create new Class"); } static { System.out.println("static block initialized"); } public int getStatic(){ return s; } public void setStatic(int i){ s=i; }
public static void main(String[] args) { // TODO Auto-generated method stub UseStatic classA= new UseStatic(); UseStatic classB= new UseStatic(); System.out.println("classA.s="+classA.getStatic()+";classB.s= "+classB.getStatic()); classA.setStatic(10); System.out.println("classA.s="+classA.getStatic()+";classB.s= "+classB.getStatic()); classB.setStatic(classB.getStatic()+10); System.out.println("classA.s="+classA.getStatic()+";classB.s= "+classB.getStatic()); } } |
下面是该程序的输出:
static block initialized Create new Class Create new Class classA.s=0;classB.s=0 classA.s=10;classB.s=10 classA.s=20;classB.s=20 |
从结果可以看出类中static块程序是在类被装载的时候开始执行。而不是在创建对象的时候执行。
来源链接:http://tb.blog.csdn.net/TrackBack.aspx?PostId=1392616