Android数据过滤器：Filter

类图：

通常可以将SearchView和ListView结合，实现数据的搜索和过滤。

1.监听SearchView，SearchView.setOnQueryTextListener(OnQueryTextListener listener)；

2.开启ListView的过滤功能，listView.setTextFilterEnabled(true)。必须开启，否则不会过滤；

3..当SearchView接收到输入事件后，调用ListView.setFilterText(filterText)方法，该方法会通过Adapter得到Filter，然后调用Filter.filter(filterText)：

<span style="font-size:14px;">    public void setFilterText(String filterText) {
            // TODO: Should we check for acceptFilter()?
            if (mTextFilterEnabled && !TextUtils.isEmpty(filterText)) {
                createTextFilter(false);
                // This is going to call our listener onTextChanged, but we might not
                // be ready to bring up a window yet
                mTextFilter.setText(filterText);
                mTextFilter.setSelection(filterText.length());
                if (mAdapter instanceof Filterable) {
                    // if mPopup is non-null, then onTextChanged will do the filtering
                    if (mPopup == null) {
                        Filter f = ((Filterable) mAdapter).getFilter();
                        f.filter(filterText);
                    }
                    // Set filtered to true so we will display the filter window when our main
                    // window is ready
                    mFiltered = true;
                    mDataSetObserver.clearSavedState();
                }
            }
        }  </span>

4.Filter.filter(filterText)方法最终会调用Filter.performFiltering(filterText)和Filter.publishResults(CharSequence filterText, FilterResults results)。performFiltering(filterText)方法完成过滤处理并且返回结果FilterResults，而publishResults(CharSequence
filterText, FilterResults results)则根据返回的结果进行相应的处理。

5.Filter.publishResults(CharSequence filterText, FilterResults results)调用了BaseAdapter.notifyDataSetChanged()方法，该方法用于当Adapter的数据发生变化时，通知UI主线程根据新的数据绘制界面：

<span style="font-size:14px;">    @Override
           protected void publishResults(CharSequence constraint, FilterResults results) {
               //noinspection unchecked
               mObjects = (List<T>) results.values;
               if (results.count > 0) {
                   notifyDataSetChanged();
               } else {
                   notifyDataSetInvalidated();
               }
           }  </span>

数据过滤就这样完成了。

下面给出例子。

布局文件filter_activity.xml：

<span style="font-size:14px;">    <?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="vertical" >  

        <SearchView
            android:id="@+id/searchView1"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content" >
        </SearchView>  

        <ListView
            android:id="@+id/listView1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" >
        </ListView>  

    </LinearLayout>  </span>

类文件MainActivity.java：

<span style="font-size:14px;">    package com.zzj.ui.filterdemo;  

    import android.app.Activity;
    import android.os.Bundle;
    import android.widget.ArrayAdapter;
    import android.widget.ListView;
    import android.widget.SearchView;
    import android.widget.SearchView.OnQueryTextListener;  

    import com.zzj.ui.R;  

    public class MainActivity extends Activity implements OnQueryTextListener {
        private ListView listView;  

        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);  

            setContentView(R.layout.filter_activity);  

            SearchView searchView = (SearchView) findViewById(R.id.searchView1);
            searchView.setOnQueryTextListener(this);
            searchView.setSubmitButtonEnabled(false);
            searchView.setIconifiedByDefault(false);  

            listView = (ListView) findViewById(R.id.listView1);  

            ArrayAdapter<String> adapter = new ArrayAdapter<String>(this,
                    android.R.layout.simple_list_item_1, new String[] { "Bei jing",
                            "Shang hai", "Chang sha", "Chang chun", "Nan jing",
                            "Dong jing", "Ji nan", "Qing dao", "Xiang tan",
                            "Zhu zhou", "Heng yang" });
            listView.setAdapter(adapter);
            // 开启过滤功能
            listView.setTextFilterEnabled(true);
        }  

        @Override
        public boolean onQueryTextSubmit(String query) {
            return false;
        }  

        @Override
        public boolean onQueryTextChange(String newText) {
            if (newText == null || newText.length() == 0) {
                listView.clearTextFilter();
            } else {
                listView.setFilterText(newText);
            }
            return true;
        }
    }  </span>

效果图：

如图所示，弹出了一个浮动框，这是listView.setFilterText(filterText)弹出来的。如果不想要这个浮动框，可以先获取Filter，然后调用Filter.filter(filterText)。

修改SearchView的监听函数如下：

    @Override
        public boolean onQueryTextChange(String newText) {
            ListAdapter adapter = listView.getAdapter();
            if (adapter instanceof Filterable) {
                Filter filter = ((Filterable) adapter).getFilter();
                if (newText == null || newText.length() == 0) {
                    filter.filter(null);
                } else {
                    filter.filter(newText);
                }
            }
            return true;
        }  

使用这种方法不需要开启ListView的过滤功能。效果如下：

上面使用的是ArrayAdapter的过滤功能，我们也可以继承BaseAdapter，然后实现Filterable接口，定义自己的过滤器。

from：http://blog.csdn.net/zhangzeyuaaa/article/details/40187789