并发修改例外：增加一个ArrayList [英] Concurrent Modification Exception : adding to an ArrayList

问题描述

该问题发生在

Element element = it.next();

这code，其中包含该行，是内部的onTouchEvent

for(Iterator<Element> it = mElements.iterator(); it.hasNext();){
                Element element = it.next();

                if(touchX > element.mX  && touchX < element.mX + element.mBitmap.getWidth() && touchY > element.mY   
                        && touchY < element.mY + element.mBitmap.getHeight()) {  

                    //irrelevant stuff..

                    if(element.cFlag){
                        mElements.add(new Element("crack",getResources(), (int)touchX,(int)touchY));
                        element.cFlag = false;

                    }           
                }
            }

所有这一切都是在同步（mElements），其中 mElements 是的ArrayList＆LT ;组件＆gt;

当我触摸元素，它可以激活 CFLAG ，这将创造另一个元素使用不同的特性，这将脱落的画面和破坏本身在不到一秒的时间。这是我创造粒子特效的方法。我们可以称之为粒子破解，像在构造函数的字符串参数。

When I touch an Element, it may activate cFlag, which will create another Element with different properties, which will fall off the screen and destroy itself in less than a second. It's my way of creating particle effects. We can call this "particle" crack, like the String parameter in the constructor.

这一切工作正常，直到我添加其他主元素。现在我有两个元素屏幕在同一时间，如果我接触最新的元素，它工作正常，并启动颗粒。

This all works fine until I add another main Element. Now I have two Elements on the screen at the same time, and if I touch the newest Element, it works fine, and launches the particles.

不过，如果我触摸并激活 CFLAG 上了年纪的元素，然后它给我的异常。

However, if I touch and activate cFlag on the older Element, then it gives me the exception.

 07-28 15:36:59.815: ERROR/AndroidRuntime(4026): FATAL EXCEPTION: main
07-28 15:36:59.815: ERROR/AndroidRuntime(4026): java.util.ConcurrentModificationException
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at java.util.ArrayList$ArrayListIterator.next(ArrayList.java:573)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at com.Juggle2.Panel.onTouchEvent(Panel.java:823)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.view.View.dispatchTouchEvent(View.java:3766)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.view.ViewGroup.dispatchTouchEvent(ViewGroup.java:863)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at com.android.internal.policy.impl.PhoneWindow$DecorView.superDispatchTouchEvent(PhoneWindow.java:1767)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at com.android.internal.policy.impl.PhoneWindow.superDispatchTouchEvent(PhoneWindow.java:1119)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.app.Activity.dispatchTouchEvent(Activity.java:2086)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at com.android.internal.policy.impl.PhoneWindow$DecorView.dispatchTouchEvent(PhoneWindow.java:1751)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.view.ViewRoot.handleMessage(ViewRoot.java:1785)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.os.Handler.dispatchMessage(Handler.java:99)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.os.Looper.loop(Looper.java:123)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at android.app.ActivityThread.main(ActivityThread.java:4627)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at java.lang.reflect.Method.invokeNative(Native Method)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at java.lang.reflect.Method.invoke(Method.java:521)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:893)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:651)
07-28 15:36:59.815: ERROR/AndroidRuntime(4026):     at dalvik.system.NativeStart.main(Native Method)

我怎样才能使这项工作？

How can I make this work?

推荐答案

<一个href="http://download.oracle.com/javase/6/docs/api/java/util/ConcurrentModificationException.html">ConcurrentModificationException当你修改列表（通过添加或删除元素），而穿越与迭代列表时发生。

ConcurrentModificationException occurs when you modify the list (by adding or removing elements) while traversing a list with Iterator.

尝试

List<Element> thingsToBeAdd = new ArrayList<Element>();
for(Iterator<Element> it = mElements.iterator(); it.hasNext();) {
    Element element = it.next();
    if(...) {  
        //irrelevant stuff..
        if(element.cFlag){
            // mElements.add(new Element("crack",getResources(), (int)touchX,(int)touchY));
            thingsToBeAdd.add(new Element("crack",getResources(), (int)touchX,(int)touchY));
            element.cFlag = false;
        }           
    }
}
mElements.addAll(thingsToBeAdd );

你也应该考虑加强对各环路，乔恩建议。

Also you should consider enhanced for each loop as Jon suggested.

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