android开发之自定义AutoCompleteTextView

AutoCompleteTextView，很多人都用过，有些情况下使用Google提供的ArrayAdapter作为适配器就可以完成需求，但是在实际开发中，我们经常需要开发自定义适配器来完成开发工作。

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今天就来看看怎么自定义这样一个AutoCompleteTextView。

假设我们有一个Book类，Book有四个属性，id,name,author,price,pinyin，我希望在AutoCompleteTextView中无论输入什么字符，都和这五个属性进行匹配，只要有一个匹配上就将该项数据显示出来。要实现的效果如下图：

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要实现这样一个功能的重点在于重写Adapter，我们自定义一个Adapter继承自BaseAdapter，同时实现过滤器Filterable。

继承BaseAdapter很好写，我们经常在ListView中使用，这里还是一样的。

继承BaseAdapter主要实现下面四个方法，books是从构造方法中传进来的数据源。

@Override
    public int getCount() {
        return books.size();
    }

    @Override
    public Object getItem(int position) {
        return books.get(position);
    }

    @Override
    public long getItemId(int position) {
        return position;
    }

    @Override
    public View getView(int position, View convertView, ViewGroup parent) {
        ViewHolder viewHolder;
        if (convertView == null) {
            viewHolder = new ViewHolder();
//          convertView = LayoutInflater.from(context).inflate(
//                  R.layout.act_item, null);
            convertView = View.inflate(context, R.layout.act_item, null);
            viewHolder.id = (TextView) convertView.findViewById(R.id.id_book);
            viewHolder.name = (TextView) convertView
                    .findViewById(R.id.name_book);
            viewHolder.author = (TextView) convertView
                    .findViewById(R.id.author_book);
            viewHolder.price = (TextView) convertView
                    .findViewById(R.id.price_book);
            convertView.setTag(viewHolder);
        } else {
            viewHolder = (ViewHolder) convertView.getTag();
        }
        Book book = books.get(position);
        viewHolder.id.setText(book.getId() + "");
        viewHolder.name.setText(book.getName());
        viewHolder.author.setText(book.getAuthor());
        viewHolder.price.setText(book.getPrice()+"");
        return convertView;
    }

    class ViewHolder {
        TextView id, name, author, price;
    }

act_item布局文件是这样的：

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="horizontal" >

    <TextView
        android:id="@+id/id_book"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1"
        android:gravity="center"
        android:text="id" />

    <TextView
        android:id="@+id/name_book"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1"
        android:gravity="center"
        android:text="name" />

    <TextView
        android:id="@+id/author_book"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1"
        android:gravity="center"
        android:text="author" />

    <TextView
        android:id="@+id/price_book"
        android:layout_width="0dp"
        android:layout_height="48dp"
        android:layout_weight="1"
        android:gravity="center"
        android:text="price" />

</LinearLayout>

同时，由于我们实现了Filterable接口，所以还要实现该接口里边的一个方法：

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

ArrayFilter是我们实现数据过滤的一个关键类，该类继承自Filter，实现其中的两个方法，第一方法时数据的过滤逻辑，第二个方法是把过滤结果赋值给数据源。

    private class ArrayFilter extends Filter {

        @Override
        protected FilterResults performFiltering(CharSequence constraint) {
            FilterResults results = new FilterResults();
            if (mFilterBooks == null) {
                mFilterBooks = new ArrayList<Book>(books);
            }
            //如果没有过滤条件则不过滤
            if (constraint == null || constraint.length() == 0) {
                results.values = mFilterBooks;
                results.count = mFilterBooks.size();
            } else {
                List<Book> retList = new ArrayList<Book>();
                //过滤条件
                String str = constraint.toString().toLowerCase();
                //循环变量数据源，如果有属性满足过滤条件，则添加到result中
                for (Book book : mFilterBooks) {
                    if (book.getAuthor().contains(str)
                            || book.getName().contains(str)
                            || (book.getId() + "").contains(str)
                            || (book.getPrice() + "").contains(str)||book.getPinyin().contains(str)) {
                        retList.add(book);
                    }
                }
                results.values = retList;
                results.count = retList.size();
            }
            return results;
        }

        //在这里返回过滤结果
        @Override
        protected void publishResults(CharSequence constraint,
                FilterResults results) {
//          notifyDataSetInvalidated()，会重绘控件（还原到初始状态）
//          notifyDataSetChanged()，重绘当前可见区域
            books = (List<Book>) results.values;
            if(results.count>0){
                notifyDataSetChanged();
            }else{
                notifyDataSetInvalidated();
            }
        }

    }

最重要的Adapter已经做好了，下来看看在MainActivity中怎么调用吧：

public class MainActivity extends Activity {

    private List<Book> books = new ArrayList<Book>();
    private AutoCompleteTextView act;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
        initView();
    }

    private void initView() {
        act = (AutoCompleteTextView) this.findViewById(R.id.myact);
        MyActAdapter adapter = new MyActAdapter(books, this);
        act.setAdapter(adapter);
        act.setThreshold(0);
    }

    private void initData() {
        Book b1 = new Book(1, "三国演义", "罗贯中", 38, "sanguoyanyi");
        Book b2 = new Book(2, "红楼梦", "曹雪芹", 25, "hongloumeng");
        Book b3 = new Book(3, "西游记", "吴承恩", 43, "xiyouji");
        Book b4 = new Book(4, "水浒传", "施耐庵", 72, "shuihuzhuan");
        Book b5 = new Book(5, "随园诗话", "袁枚", 32, "suiyuanshihua");
        Book b6 = new Book(6, "说文解字", "许慎", 14, "shuowenjiezi");
        Book b7 = new Book(7, "文心雕龙", "刘勰", 18, "wenxindiaolong");
        books.add(b1);
        books.add(b2);
        books.add(b3);
        books.add(b4);
        books.add(b5);
        books.add(b6);
        books.add(b7);
    }
}

布局文件：

public class MainActivity extends Activity {

    private List<Book> books = new ArrayList<Book>();
    private AutoCompleteTextView act;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initData();
        initView();
    }

    private void initView() {
        act = (AutoCompleteTextView) this.findViewById(R.id.myact);
        MyActAdapter adapter = new MyActAdapter(books, this);
        act.setAdapter(adapter);
        act.setThreshold(0);
    }

    private void initData() {
        Book b1 = new Book(1, "三国演义", "罗贯中", 38, "sanguoyanyi");
        Book b2 = new Book(2, "红楼梦", "曹雪芹", 25, "hongloumeng");
        Book b3 = new Book(3, "西游记", "吴承恩", 43, "xiyouji");
        Book b4 = new Book(4, "水浒传", "施耐庵", 72, "shuihuzhuan");
        Book b5 = new Book(5, "随园诗话", "袁枚", 32, "suiyuanshihua");
        Book b6 = new Book(6, "说文解字", "许慎", 14, "shuowenjiezi");
        Book b7 = new Book(7, "文心雕龙", "刘勰", 18, "wenxindiaolong");
        books.add(b1);
        books.add(b2);
        books.add(b3);
        books.add(b4);
        books.add(b5);
        books.add(b6);
        books.add(b7);
    }
}

好了，就是这么简单，不过这里有一个最大的缺憾就是我们的数据源中本身带有一个pinyin属性，在实际的开发中肯定不能这样，那么我们怎么实现通过汉字首字母来搜索呢？比如输入sg，就会提示“三国演义”。我会在下篇文章中介绍怎么通过Java类来实现这么一个功能。

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