使用自定义适配器的AutoCompleteTextView ClassCastException异常 [英] ClassCastException using a custom adapter for an AutoCompleteTextView

问题描述

在Xamarin，我有一个AutoCompleteTextView自定义适配器的麻烦。

In Xamarin, I am having trouble with a custom adapter for a AutoCompleteTextView.

下面是我的code：

private void SetupAutoCompleteTextViewWithCustomAdapter()
{
    List<CustomItem> customItems = new List<CustomItem>();

    CustomItem customItem = new CustomItem();
    customItem.Heading = "TestHeading";
    customItem.SubHeading = "TestSubHeading";
    customItems.Add(customItem);

    customItem = new CustomItem();
    customItem.Heading = "TestHeading 2";
    customItem.SubHeading = "TestSubHeading 2";
    customItems.Add(customItem);

    customItem = new CustomItem();
    customItem.Heading = "TestHeading 3";
    customItem.SubHeading = "TestSubHeading 3";
    customItems.Add(customItem);

    AutoCompleteTextView AutoCompleteTextViewWithCustomAdapter = (AutoCompleteTextView) FindViewById(Resource.Id.AutoCompleteTextView);
    AutoCompleteTextViewWithCustomAdapter.Adapter = new CustomAdapter (this, customItems);

}

下面是我的自定义适配器：

Here is my custom adapter:

public class CustomAdapter : BaseAdapter<CustomItem> {
    List<CustomItem> items;
    Activity context;
    public CustomAdapter(Activity context, List<CustomItem> items)
        : base()
    {
        this.context = context;
        this.items = items;
    }
    public override long GetItemId(int position)
    {
        return position;
    }
    public override CustomItem this[int position]
    {
        get { return items[position]; }
    }
    public override int Count
    {
        get { return items.Count; }
    }
    public override View GetView(int position, View convertView, ViewGroup parent)
    {
        var item = items[position];

        View view = convertView;
        if (view == null) // no view to re-use, create new
            view = context.LayoutInflater.Inflate(Resource.Layout.CustomView, null);
        view.FindViewById<TextView>(Resource.Id.TextViewMapHeading).Text = item.Heading;
        view.FindViewById<TextView> (Resource.Id.TextViewMapHeading).TextSize = 20;
        view.FindViewById<TextView>(Resource.Id.TextViewItem).Text = item.SubHeading;
        view.FindViewById<ImageView>(Resource.Id.Image).SetImageResource(item.ImageResourceId);

        return view;
    }
}

下面是我的自定义项目类：

Here is my custom item class:

public class CustomItem
{
    public string Heading { get; set; }
    public string SubHeading { get; set; }
    public int ImageResourceId { get; set; }
}

下面是我的CustomView布局文件：

Here is my CustomView layout file:

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="wrap_content"
    android:padding="8dp">
    <LinearLayout
        android:id="@+id/Text"
        android:orientation="vertical"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:paddingLeft="10dip">
        <TextView
            android:id="@+id/TextViewMapHeading"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:textSize="28sp" />
        <TextView
            android:id="@+id/TextViewItem"
            android:layout_width="fill_parent"
            android:layout_height="wrap_content"
            android:autoLink="all" />
    </LinearLayout>
    <ImageView
        android:id="@+id/Image"
        android:layout_width="48dp"
        android:layout_height="48dp"
        android:padding="5dp"
        android:src="@drawable/icon"
        android:visibility="invisible"
        android:layout_alignParentRight="true" />
</RelativeLayout>

下面是我得到的错误：

java.lang.ClassCastException：simplemapdemo.CustomAdapter不能
  转换为android.widget.Filterable

java.lang.ClassCastException: simplemapdemo.CustomAdapter cannot be cast to android.widget.Filterable

我可以请有一定的帮助得到这个工作？

Can I please have some help to get this working?

在此先感谢

推荐答案

由于该适配器用于 AutoCompleteTextView 必须是工具可筛选接口，所以修改 CustomAdapter 类似以下内容：

Because the Adapter used for AutoCompleteTextView must be implements Filterable interface, so modify your CustomAdapter like following:

public class CustomAdapter extends BaseAdapter<CustomItem> implements Filterable {

    ArrayFilter mFilter;
    ...

    // please override other method in BaseAdatper as your need
    ...

    @Override
    public Filter getFilter() {
        if (mFilter == null) {
            mFilter = new ArrayFilter();
        }
        return mFilter;
    }

    // you can modify the custom Filter used for AutoCompleteTextView as your need
    private class ArrayFilter extends Filter {
        @Override
        protected FilterResults performFiltering(CharSequence prefix) {
            FilterResults results = new FilterResults();

            if (mOriginalValues == null) {
                synchronized (mLock) {
                    mOriginalValues = new ArrayList<T>(mObjects);
                }
            }

            if (prefix == null || prefix.length() == 0) {
                ArrayList<T> list;
                synchronized (mLock) {
                    list = new ArrayList<T>(mOriginalValues);
                }
                results.values = list;
                results.count = list.size();
            } else {
                String prefixString = prefix.toString().toLowerCase();

                ArrayList<T> values;
                synchronized (mLock) {
                    values = new ArrayList<T>(mOriginalValues);
                }

                final int count = values.size();
                final ArrayList<T> newValues = new ArrayList<T>();

                for (int i = 0; i < count; i++) {
                    final T value = values.get(i);
                    final String valueText = value.toString().toLowerCase();

                    // First match against the whole, non-splitted value
                    if (valueText.startsWith(prefixString)) {
                        newValues.add(value);
                    } else {
                        final String[] words = valueText.split(" ");
                        final int wordCount = words.length;

                        // Start at index 0, in case valueText starts with space(s)
                        for (int k = 0; k < wordCount; k++) {
                            if (words[k].startsWith(prefixString)) {
                                newValues.add(value);
                                break;
                            }
                        }
                    }
                }

                results.values = newValues;
                results.count = newValues.size();
            }

            return results;
        }

        @Override
        protected void publishResults(CharSequence constraint, FilterResults results) {
            //noinspection unchecked
            mObjects = (List<T>) results.values;
            if (results.count > 0) {
                notifyDataSetChanged();
            } else {
                notifyDataSetInvalidated();
            }
        }
    }
}

您可以参阅 ArrayAdapter 的源$ C ​​$ C。

You can refer to the ArrayAdapter's source code.

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