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我在从FragmentActivity向前和向后导航时收到异常，其中包含 ListView 和从自定义 Loader 加载的数据（它是从本地 sqlite 数据库加载），并且不知道如何处理它......

这是一个堆栈跟踪：

Uncaught exception: Unable to destroy activity {com.snyer.bestprice/com.snyer.bestprice.PriceTracerActivity}: java.lang.RuntimeException: Unable to destroy activity {com.snyer.bestprice/com.snyer.bestprice.CartFragmentActivity}: java.util.ConcurrentModificationException
java.lang.RuntimeException: Unable to destroy activity {com.snyer.bestprice/com.snyer.bestprice.PriceTracerActivity}: java.lang.RuntimeException: Unable to destroy activity {com.snyer.bestprice/com.snyer.bestprice.CartFragmentActivity}: java.util.ConcurrentModificationException
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3106)
    at android.app.ActivityThread.handleDestroyActivity(ActivityThread.java:3171)
    at android.app.ActivityThread.access$2100(ActivityThread.java:132)
    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1071)
    at android.os.Handler.dispatchMessage(Handler.java:99)
    at android.os.Looper.loop(Looper.java:150)
    at android.app.ActivityThread.main(ActivityThread.java:4293)
    at java.lang.reflect.Method.invokeNative(Native Method)
    at java.lang.reflect.Method.invoke(Method.java:507)
    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:849)
    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:607)
    at dalvik.system.NativeStart.main(Native Method)
Caused by: java.lang.RuntimeException: Unable to destroy activity {com.snyer.bestprice/com.snyer.bestprice.CartFragmentActivity}: java.util.ConcurrentModificationException
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3106)
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:2994)
    at android.app.LocalActivityManager.dispatchDestroy(LocalActivityManager.java:625)
    at android.app.ActivityGroup.onDestroy(ActivityGroup.java:85)
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3088)
    ... 11 more
Caused by: java.util.ConcurrentModificationException
    at java.util.ArrayList$ArrayListIterator.next(ArrayList.java:576)
    at android.database.DataSetObservable.notifyInvalidated(DataSetObservable.java:42)
    at android.widget.BaseAdapter.notifyDataSetInvalidated(BaseAdapter.java:54)
    at android.support.v4.widget.CursorAdapter.swapCursor(CursorAdapter.java:352)
    at com.snyer.bestprice.CartFragmentActivity.onLoaderReset(CartFragmentActivity.java:412)
    at android.support.v4.app.LoaderManagerImpl$LoaderInfo.destroy(LoaderManager.java:337)
    at android.support.v4.app.LoaderManagerImpl.doDestroy(LoaderManager.java:773)
    at android.support.v4.app.FragmentActivity.onDestroy(FragmentActivity.java:318)
    at android.app.ActivityThread.performDestroyActivity(ActivityThread.java:3088)
    ... 15 more

mCartCursorAdapter.swapCursor(null);此代码片段 (CartFragmentActivity.java:412)行发生异常：

public void onLoaderReset(Loader<Cursor> loader) {
    switch (loader.getId()) {
    case LOADER_CART_LIST_ID:
        mCartListCursorAdapter.swapCursor(null);
        break;

    case LOADER_CART_CONTENTS_ID:
        mCartCursorAdapter.swapCursor(null);
        break;
    }
}

在这里可以做些什么来消除这个异常？

4

3 回答 3

4

sdk 源提供了一个很好的提示作为评论：

在 Android 4.0.4 中是：

public void notifyInvalidated() {
    synchronized(mObservers) {
        for (int i = mObservers.size() - 1; i >= 0; i--) {
            mObservers.get(i).onInvalidated();
        }
    }
}

在早期版本中，它是：

 synchronized (mObservers) {
        for (DataSetObserver observer : mObservers) {
            observer.onInvalidated();
        }
    }

4.0.4 源对 onChange 方法的相同更改有以下评论：

// since onChanged() is implemented by the app, it could do anything, including
// removing itself from {@link mObservers} - and that could cause problems if
// an iterator is used on the ArrayList {@link mObservers}.
// to avoid such problems, just march thru the list in the reverse order.

我不知道以任何非法方式操纵观察者的 ArrayList。由于这在以后的 API 中得到了解决，而且我想不出对我的应用程序有任何影响，我想我只是简单地忽略带有日志条目或类似内容的异常。

于 2012-11-09T13:04:14.883 回答
0

可能是onLoaderReset()在后台线程上被Loader. 尝试使用runOnUiThread()或类似机制将您的swapCursor()调用移至主应用程序线程。

于 2012-10-08T11:19:54.210 回答
0

最快的方法是DataSetObservable从“正确”版本的 sdk 复制到您的应用程序并使用它。DataSetObservable应该是这样的：

public class DataSetObservable extends Observable<DataSetObserver> {
/**
 * Invokes {@link DataSetObserver#onChanged} on each observer.
 * Called when the contents of the data set have changed.  The recipient
 * will obtain the new contents the next time it queries the data set.
 */
public void notifyChanged() {
    synchronized(mObservers) {
        // since onChanged() is implemented by the app, it could do anything, including
        // removing itself from {@link mObservers} - and that could cause problems if
        // an iterator is used on the ArrayList {@link mObservers}.
        // to avoid such problems, just march thru the list in the reverse order.
        for (int i = mObservers.size() - 1; i >= 0; i--) {
            mObservers.get(i).onChanged();
        }
    }
}

/**
 * Invokes {@link DataSetObserver#onInvalidated} on each observer.
 * Called when the data set is no longer valid and cannot be queried again,
 * such as when the data set has been closed.
 */
public void notifyInvalidated() {
    synchronized (mObservers) {
        for (int i = mObservers.size() - 1; i >= 0; i--) {
            mObservers.get(i).onInvalidated();
        }
    }
}

在您的情况下，您也应该从源代码中复制 BaseAdapter 。并将它的 android 更改DataSetObservable为您的应用程序DataSetObservable。

于 2013-10-07T16:35:43.087 回答