Question

我尝试调试几个代码并给出并发修改异常

码

final GestureLibrary store1 = GestureLibraries.fromFile(new File(Environment.getExternalStorageDirectory(), "Gesture_launcher"));

     if (store1.load()) 
     {
        for (String name : store1.getGestureEntries()) 
        {
             for (Gesture gesture : store1.getGestures(name)) 
             {
                 if(name.contains(gesture_name))
                 {
                     store1.removeGesture(name, gesture);
                     store1.addGesture(name, mGesture);
                     store1.save();

                     Toast.makeText(getApplicationContext(), getResources().getString(R.string.saved), Toast.LENGTH_LONG).show();
                 }
             }
        }
     }

执行上述语句会产生concurrentModificationException

logcat的

03-28 02:47:45.422: E/AndroidRuntime(449): FATAL EXCEPTION: main
03-28 02:47:45.422: E/AndroidRuntime(449): java.util.ConcurrentModificationException
03-28 02:47:45.422: E/AndroidRuntime(449):  at java.util.HashMap$HashIterator.nextEntry(HashMap.java:796)
03-28 02:47:45.422: E/AndroidRuntime(449):  at java.util.HashMap$KeyIterator.next(HashMap.java:823)
03-28 02:47:45.422: E/AndroidRuntime(449):  at com.likith.gesturebuilder.change_gestures.setGestures(change_gestures.java:69)
03-28 02:47:45.422: E/AndroidRuntime(449):  at com.likith.gesturebuilder.change_gestures$1.onClick(change_gestures.java:110)
03-28 02:47:45.422: E/AndroidRuntime(449):  at android.view.View.performClick(View.java:2485)
03-28 02:47:45.422: E/AndroidRuntime(449):  at android.view.View$PerformClick.run(View.java:9080)
03-28 02:47:45.422: E/AndroidRuntime(449):  at android.os.Handler.handleCallback(Handler.java:587)
03-28 02:47:45.422: E/AndroidRuntime(449):  at android.os.Handler.dispatchMessage(Handler.java:92)
03-28 02:47:45.422: E/AndroidRuntime(449):  at android.os.Looper.loop(Looper.java:123)
03-28 02:47:45.422: E/AndroidRuntime(449):  at android.app.ActivityThread.main(ActivityThread.java:3683)
03-28 02:47:45.422: E/AndroidRuntime(449):  at java.lang.reflect.Method.invokeNative(Native Method)
03-28 02:47:45.422: E/AndroidRuntime(449):  at java.lang.reflect.Method.invoke(Method.java:507)
03-28 02:47:45.422: E/AndroidRuntime(449):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:839)
03-28 02:47:45.422: E/AndroidRuntime(449):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:597)
03-28 02:47:45.422: E/AndroidRuntime(449):  at dalvik.system.NativeStart.main(Native Method)

请告诉我们如何避免此异常的任何方法谢谢

编辑1： 现在我修改了代码

List<Gesture> list = store1.getGestures(gesture_name);
         Set<String> List_name = store1.getGestureEntries();

         for (String name : List_name) 
         {
             for (Gesture gesture : list) 
             {
                 if(name.contains(gesture_name))
                 {
                     store1.removeGesture(name, gesture);
                     store1.addGesture(name, mGesture);
                     store1.save();

                     Toast.makeText(getApplicationContext(), getResources().getString(R.string.saved), Toast.LENGTH_LONG).show();
                 }
             }
        }

它再次给了我同样的错误。

Answer 1

您在调用store1.removeGesture（）和store1.addGesture（）的同时循环遍历store1.getGestures（）。

尝试复制手势数组并循环复制。

Array<Gesture> newArray = new Array<>();
newArray.addAll(store1.getGestures(name));
for (Gesture gesture : newArray) 
         {
             if(name.contains(gesture_name))
             {
                 store1.removeGesture(name, gesture);
                 store1.addGesture(name, mGesture);
                 store1.save();
...

Answer 2

避免并发修改异常的一种简单方法是使用常规for循环。

使用ehanced for循环时，使用迭代器。使用迭代器时，不允许修改集合。

常规for循环看起来像这样

List<String> list;

for(int i = 0; i < list.size(); i++) {
    String string = list.get(i);
    //use string
}

与使用增强的for循环相反，它看起来像这样

List<String> list;

for(String string : list) {
     //use string
}

避免并发修改异常

2 个答案: