Android ListView用EditText实现搜索功能效

在查阅资料以后，发现其实Android中已经帮我们实现了这个功能，如果你的ListView使用的是系统的ArrayAdapter，那么恭喜你，下面的事情就很简单了，你只需要调用下面的代码就可以实现了：

<pre class="brush:java;">searchEdittext.addTextChangedListener(new TextWatcher() {
@Override
public void onTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
// When user change the text
mAdapter.getFilter().filter(cs);
}

@Override
public void beforeTextChanged(CharSequence cs, int arg1, int arg2, int arg3) {
//
}

@Override
public void afterTextChanged(Editable arg0) {
//
}
});
</pre>

你没看错，就一行 mAdapter.getFilter().filter(cs);便可以实现这个搜索功能。不过我相信大多数Adapter都是自定义的，基于这个需求，我去分析了下ArrayAdapter，发现它实现了Filterable接口，那么接下来的事情就比较简单了，就让我们自定的Adapter也去实现Filterable这个接口，不久可以实现这个需求了吗。下面贴出ArrayAdapter中显示过滤功能的关键代码：

<pre class="brush:java;">public class ArrayAdapter<T> extends BaseAdapter implements Filterable {
/**

• Contains the list of objects that represent the data of this ArrayAdapter.
• The content of this list is referred to as "the array" in the documentation.
  */
  private List<T> mObjects;

/**

• Lock used to modify the content of {@link #mObjects}. Any write operation
• performed on the array should be synchronized on this lock. This lock is also
• used by the filter (see {@link #getFilter()} to make a synchronized copy of
• the original array of data.
  */
  private final Object mLock = new Object();

// A copy of the original mObjects array, initialized from and then used instead as soon as
// the mFilter ArrayFilter is used. mObjects will then only contain the filtered values.
private ArrayList<T> mOriginalValues;
private ArrayFilter mFilter;

...

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

/**

• <p>An array filter constrains the content of the array adapter with

• a prefix. Each item that does not start with the supplied prefix

• is removed from the list.</p>
  */
  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();
  }
}

}
}

</pre>

实现

首先写了一个Model（User）模拟数据

<pre class="brush:java;">public class User {
private int avatarResId;
private String name;

public User(int avatarResId, String name) {
this.avatarResId = avatarResId;
this.name = name;
}

public int getAvatarResId() {
return avatarResId;
}

public void setAvatarResId(int avatarResId) {
this.avatarResId = avatarResId;
}

public String getName() {
return name;
}

public void setName(String name) {
this.name = name;
}
}

</pre>

自定义一个Adapter（UserAdapter）继承自BaseAdapter，实现了Filterable接口，Adapter一些常见的处理，我都去掉了，这里主要讲讲Filterable这个接口。

<pre class="brush:java;">/**

• Contains the list of objects that represent the data of this Adapter.
• Adapter数据源
  */
  private List<User> mDatas;

//过滤相关
/**

• This lock is also used by the filter
• (see {@link #getFilter()} to make a synchronized copy of
• the original array of data.
• 过滤器上的锁可以同步复制原始数据。

*/
private final Object mLock = new Object();

// A copy of the original mObjects array, initialized from and then used instead as soon as
// the mFilter ArrayFilter is used. mObjects will then only contain the filtered values.
//对象数组的备份，当调用ArrayFilter的时候初始化和使用。此时，对象数组只包含已经过滤的数据。
private ArrayList<User> mOriginalValues;
private ArrayFilter mFilter;

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

</pre>

写一个ArrayFilter类继承自Filter类，我们需要两个方法：

<pre class="brush:java;">//执行过滤的方法
protected FilterResults performFiltering(CharSequence prefix);</pre>

<pre class="brush:java;">//得到过滤结果
protected void publishResults(CharSequence prefix, FilterResults results);</pre>

贴上完整的代码，注释已经写的不能再详细了

<pre class="brush:java;"> /**

• 过滤数据的类
  /
  /*

• <p>An array filter constrains the content of the array adapter with

• a prefix. Each item that does not start with the supplied prefix

• is removed from the list.</p>

• <p/>

• 一个带有首字母约束的数组过滤器，每一项不是以该首字母开头的都会被移除该list。
  */
  private class ArrayFilter extends Filter {
  //执行刷选
  @Override
  protected FilterResults performFiltering(CharSequence prefix) {
  FilterResults results = new FilterResults();//过滤的结果
  //原始数据备份为空时，上锁，同步复制原始数据
  if (mOriginalValues == null) {
  synchronized (mLock) {
  mOriginalValues = new ArrayList<>(mDatas);
  }
  }
  //当首字母为空时
  if (prefix == null || prefix.length() == 0) {
  ArrayList<User> list;
  synchronized (mLock) {//同步复制一个原始备份数据
  list = new ArrayList<>(mOriginalValues);
  }
  results.values = list;
  results.count = list.size();//此时返回的results就是原始的数据，不进行过滤
  } else {
  String prefixString = prefix.toString().toLowerCase();//转化为小写

  ArrayList<User> values;
  synchronized (mLock) {//同步复制一个原始备份数据
  values = new ArrayList<>(mOriginalValues);
  }
  final int count = values.size();
  final ArrayList<User> newValues = new ArrayList<>();

  for (int i = 0; i < count; i++) {
  final User value = values.get(i);//从List<User>中拿到User对象
  // final String valueText = value.toString().toLowerCase();
  final String valueText = value.getName().toString().toLowerCase();//User对象的name属性作为过滤的参数
  // First match against the whole, non-splitted value
  if (valueText.startsWith(prefixString) || valueText.indexOf(prefixString.toString()) != -1) {//第一个字符是否匹配
  newValues.add(value);//将这个item加入到数组对象中
  } else {//处理首字符是空格
  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)) {//一旦找到匹配的就break，跳出for循环
         newValues.add(value);
         break;
       }
     }
   }
  

  }
  results.values = newValues;//此时的results就是过滤后的List<User>数组
  results.count = newValues.size();
  }
  return results;
  }

//刷选结果
@Override
protected void publishResults(CharSequence prefix, FilterResults results) {
  //noinspection unchecked
  mDatas = (List<User>) results.values;//此时，Adapter数据源就是过滤后的Results
  if (results.count > 0) {
    notifyDataSetChanged();//这个相当于从mDatas中删除了一些数据，只是数据的变化，故使用notifyDataSetChanged()
  } else {
    /**
     * 数据容器变化 ----> notifyDataSetInValidated

     容器中的数据变化 ----> notifyDataSetChanged
     */
    notifyDataSetInvalidated();//当results.count<=0时，此时数据源就是重新new出来的，说明原始的数据源已经失效了
  }
}

}

</pre>

特别说明

<pre class="brush:java;">//User对象的name属性作为过滤的参数
final String valueText = value.getName().toString().toLowerCase();</pre>

这个地方是，你要进行搜索的关键字，比如我这里使用的是User对象的Name属性，就是把用户名当作关键字来进行过滤筛选的。这里要根据你自己的具体逻辑来进行设置。

<a onclick="doCopy('code18366')" id="copybut18366" class="copybut" style="CURSOR: pointer" data="18366"><u>复制代码</u></a>

代码如下:

if (valueText.startsWith(prefixString) || valueText.indexOf(prefixString.toString()) != -1)

在这里进行关键字匹配，如果你只想使用第一个字符匹配，那么你只需要使用这行代码就可以了：

<pre class="brush:java;">//首字符匹配
valueText.startsWith(prefixString)</pre>

如果你的需求是只要输入的字符出现在ListView列表中，那么该item就要显示出来，那么你就需要这行代码了：

<pre class="brush:java;">//你输入的关键字包含在了某个item中，位置不做考虑，即可以不是第一个字符
valueText.indexOf(prefixString.toString()) != -1</pre>

这样就完成了一个EditText + ListView实现搜索的功能。