Question

我想为GridView添加页脚视图。

我在文档中发现GridView有2个继承的 addView（View child）方法。

From class android.widgetAdapterView

void addView(View child)

This method is not supported and throws an UnsupportedOperationException when called.

和

From class android.view.ViewGroup

void addView(View child)

Adds a child view.

似乎我应该使用后者。但是如何调用这个特定的继承方法呢？

Answer 1

你不是。它会用UnsupportedOperationException覆盖原文，因为它很好..不支持。

您应该编辑适配器。根据您的实施情况，这看起来会有所不同。但是，您只需向适配器添加更多数据，并在适配器上调用.notifyDataSetChanged()，GridView将自行添加视图。

页脚视图应该是View之后的单独GridView，或者您必须在适配器列表中保持其位置，以便在添加新项目时始终为最后一个。

Answer 2

提供Erics解决方案的示例，适配器可以维护两个额外的成员来跟踪 “页脚”的位置及其事件处理程序：

class ImageViewGridAdapter : ArrayAdapter<int>
{
    private readonly List<int> images;

    public int EventHandlerPosition { get; set; }
    public EventHandler AddNewImageEventHandler { get; set; }

    public ImageViewGridAdapter(Context context, int textViewResourceId, List<int> images)
        : base(context, textViewResourceId, images)
    {
        this.images = images;
    }

    public override View GetView(int position, View convertView, ViewGroup parent)
    {
        ImageView v = (ImageView)convertView;

        if (v == null)
        {
            LayoutInflater li = (LayoutInflater)this.Context.GetSystemService(Context.LayoutInflaterService);
            v = (ImageView)li.Inflate(Resource.Layout.GridItem_Image, null);

            // ** Need to assign event handler in here, since GetView 
            // is called an arbitrary # of times, and the += incrementor
            // will result in multiple event fires

            // Technique 1 - More flexisble, more maintenance ////////////////////
            if (position == EventHandlerPosition)            
                v.Click += AddNewImageEventHandler;

            // Technique 2 - less flexible, less maintenance /////////////////////
            if (position == images.Count)
                v.Click += AddNewImageEventHandler;
        }

        if (images[position] != null)
        {
            v.SetBackgroundResource(images[position]);
        }

        return v;
    }
}

然后，在将适配器分配给网格视图之前，只需分配这些值（位置不必在结尾，但对于页脚应该是）：

List<int> images = new List<int> { 
    Resource.Drawable.image1, Resource.Drawable.image2, Resource.Drawable.image_footer 
};

ImageViewGridAdapter recordAttachmentsAdapter = new ImageViewGridAdapter(Activity, 0, images);

recordAttachmentsAdapter.EventHandlerPosition = images.Count;
recordAttachmentsAdapter.AddNewImageEventHandler += NewAttachmentClickHandler;

_recordAttachmentsGrid.Adapter = recordAttachmentsAdapter;

addView for GridView

2 个答案: