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。
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：
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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