在GridView中膨胀FrameLayout时出现ClassCastException

Question

我正在尝试在GridView中膨胀FrameLayout并且我得到一个例外.这是来自适配器的getView方法(BaseAdapter的子类):

public View getView(int position, View convertView, ViewGroup parent) {
    // TODO: Create compound view with image and name overlayed on top
    FrameLayout personFrame;
    if (convertView == null) {
        LayoutInflater inflater = (LayoutInflater)mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
        personFrame = (FrameLayout)inflater.inflate(R.layout.thumbnail, null);
        //personFrame = (FrameLayout)View.inflate(mContext, R.layout.thumbnail, null);
        personFrame.setLayoutParams(new GridView.LayoutParams(85,85));
    } else {
        personFrame = (FrameLayout) convertView;
    }

.... 等等

这是我正在膨胀的布局:

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="85px"
android:layout_height="85px">
<ImageView
    android:id="@+id/thumbnail_image"
    android:layout_height="85px"
    android:padding="2px"
    android:layout_width="85px"
    android:scaleType="centerCrop" />
<TextView
    android:id="@+id/person_name"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="2dip"
    android:layout_gravity="center_horizontal|bottom"

    android:padding="2dip"

    android:background="#AA000000"
    android:textColor="#ffffffff"

    android:text="Me" />
</FrameLayout>

我已尝试使用和不使用显式设置LayoutParams,每次都得到相同的异常,这是:

E/AndroidRuntime(  420): java.lang.ClassCastException:        android.widget.FrameLayout$LayoutParams
E/AndroidRuntime(  420):    at android.widget.GridView.onMeasure(GridView.java:934)
E/AndroidRuntime(  420):    at android.view.View.measure(View.java:8171)
E/AndroidRuntime(  420):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
E/AndroidRuntime(  420):    at android.widget.LinearLayout.measureChildBeforeLayout(LinearLayout.java:1012)
E/AndroidRuntime(  420):    at android.widget.LinearLayout.measureVertical(LinearLayout.java:381)
E/AndroidRuntime(  420):    at android.widget.LinearLayout.onMeasure(LinearLayout.java:304)
E/AndroidRuntime(  420):    at android.view.View.measure(View.java:8171)
E/AndroidRuntime(  420):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
E/AndroidRuntime(  420):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
E/AndroidRuntime(  420):    at android.view.View.measure(View.java:8171)
E/AndroidRuntime(  420):    at android.view.ViewGroup.measureChildWithMargins(ViewGroup.java:3132)
E/AndroidRuntime(  420):    at android.widget.FrameLayout.onMeasure(FrameLayout.java:245)
E/AndroidRuntime(  420):    at android.view.View.measure(View.java:8171)
E/AndroidRuntime(  420):    at android.view.ViewRoot.performTraversals(ViewRoot.java:801)
E/AndroidRuntime(  420):    at android.view.ViewRoot.handleMessage(ViewRoot.java:1727)
E/AndroidRuntime(  420):    at android.os.Handler.dispatchMessage(Handler.java:99)
E/AndroidRuntime(  420):    at android.os.Looper.loop(Looper.java:123)
E/AndroidRuntime(  420):    at android.app.ActivityThread.main(ActivityThread.java:4627)
E/AndroidRuntime(  420):    at java.lang.reflect.Method.invokeNative(Native Method)
E/AndroidRuntime(  420):    at java.lang.reflect.Method.invoke(Method.java:521)
E/AndroidRuntime(  420):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:868)
E/AndroidRuntime(  420):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:626)
E/AndroidRuntime(  420):    at dalvik.system.NativeStart.main(Native Method)

任何人都可以指出我在哪里出错吗？非常感谢

Answer 1

实际上从getView返回错误的对象(正如你提到的那样)是导致异常的原因.例如,如果从FrameLayout而不是FrameLayout本身返回一个按钮,则会导致您描述的问题.GridView代码将返回您返回的View对象,并向View层次结构向上移动一步.它期望找到一个AbsListView(它包装每个网格视图项).因为您返回了FrameLayout的子元素,所以GridView类找到了一个它期望AbsListView的FrameLayout.

Answer 2

尝试改变:

personFrame.setLayoutParams(new GridView.LayoutParams(85,85));

至:

personFrame.setLayoutParams(new AbsListView.LayoutParams(85,85));

看来,当你设置LayoutParams一个对象时,它应该可以转换为父对象LayoutParams.在您的情况下,父级personFrame是网格视图.

Answer 3

GridView 不是 FrameLayout，两者都是 ViewGroup，但它不是 FrameLayout。