Android ListView 用 EditText 实现搜索功能

问题描述

我最近遇到这样一个问题：ListView 显示城市列表，上面有个 EditText 控件，当在 EditText 输入关键字如‘南’时，ListView 重新显示与此相关的城市列表，从而实现搜索功能。

由于 ListView 用的是系统的 ArrayAdapter,它实现 Filterable 接口，所以这个问题就简单很多了，只需要监听 Edittext 的输入就可以了。

方案

下面是关键代码：

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) {
        //
    }
});

如果是自定义的Adapter，也可以实现Filterable接口

下面给出ArrayAdapter源码中过滤的关键部分：

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();
            }
        }
    }
}