BaseAdapter getView类异常

Question

我尝试在BaseAdapter的getView方法中根据位置返回两种不同类型的视图。

但我得到了ClassCastException。下面是我的代码：

public View getView(final int position, View convertView, ViewGroup parent) {
    if(position != 5){

        WebPageView web;
        if(convertView == null){

            web = new WebPageView(mContext, new Point(parent.getWidth(), parent.getHeight()), parent);

    } else {
        web = (WebPageView) convertView;

    }

        web.setPage("http://yahoo.com");
        return web;
    }else{
    final PageView pageView;
    if (convertView == null) {
        pageView = new PageView(mContext);
    } else {
        pageView = (PageView) convertView;
    }


    return pageView;
}
}

但我得到的总是ClassCastException。当我在getView中单独使用WebPageView或PageView时，我没有得到异常。

有谁知道吗？

下面是我的logcat输出。

10-18 18:03:59.250: E/AndroidRuntime(31390): FATAL EXCEPTION: main
10-18 18:03:59.250: E/AndroidRuntime(31390): java.lang.ClassCastException: com.getit.WebPageView cannot be cast to com.getit.PageView
10-18 18:03:59.250: E/AndroidRuntime(31390):    at com.getit.PageAdapter.getView(PageAdapter.java:94)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at com.getit.CustomGalleryView.getOrCreateChild(CustomGalleryView.java:467)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at com.getit.CustomGalleryView.onLayout(CustomGalleryView.java:422)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.View.layout(View.java:13754)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewGroup.layout(ViewGroup.java:4364)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.widget.RelativeLayout.onLayout(RelativeLayout.java:948)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.View.layout(View.java:13754)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewGroup.layout(ViewGroup.java:4364)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.View.layout(View.java:13754)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewGroup.layout(ViewGroup.java:4364)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.widget.LinearLayout.setChildFrame(LinearLayout.java:1649)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.widget.LinearLayout.layoutVertical(LinearLayout.java:1507)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.widget.LinearLayout.onLayout(LinearLayout.java:1420)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.View.layout(View.java:13754)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewGroup.layout(ViewGroup.java:4364)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.widget.FrameLayout.onLayout(FrameLayout.java:448)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.View.layout(View.java:13754)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewGroup.layout(ViewGroup.java:4364)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewRootImpl.performLayout(ViewRootImpl.java:1868)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewRootImpl.performTraversals(ViewRootImpl.java:1689)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewRootImpl.doTraversal(ViewRootImpl.java:1000)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.ViewRootImpl$TraversalRunnable.run(ViewRootImpl.java:4214)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.Choreographer$CallbackRecord.run(Choreographer.java:725)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.Choreographer.doCallbacks(Choreographer.java:555)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.Choreographer.doFrame(Choreographer.java:525)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.view.Choreographer$FrameDisplayEventReceiver.run(Choreographer.java:711)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.os.Handler.handleCallback(Handler.java:615)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.os.Handler.dispatchMessage(Handler.java:92)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.os.Looper.loop(Looper.java:137)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at android.app.ActivityThread.main(ActivityThread.java:4745)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at java.lang.reflect.Method.invokeNative(Native Method)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at java.lang.reflect.Method.invoke(Method.java:511)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:786)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:553)
10-18 18:03:59.250: E/AndroidRuntime(31390):    at dalvik.system.NativeStart.main(Native Method)

Answer 1

你得到这个错误是因为你试图回收一个已经转换为另一个对象的视图。我不知道你是否使用了自定义对象，就好像两者都在扩展一个公共类，它会让worked.You做两件事：

1:检查convertview是否是自定义object.This的版本，确保您不会尝试将pageview转换为webview，反之亦然

if (convertView == null || !convertView instanceof PageView) {
    pageView = new PageView(mContext);
} else {
    pageView = (PageView) convertView;
}

同样的webview检查也是如此。

2:每次创建新对象时实例化

if(position != 5){
WebPageView web;
web = new WebPageView(mContext, new Point(parent.getWidth(), parent.getHeight()), parent);
web.setPage("http://yahoo.com");
return web;
}else{
final PageView pageView;
pageView = new PageView(mContext);
return pageView;
}

不是很明智，但还是...