前言
最近在開(kāi)發(fā)一個(gè)IM項(xiàng)目的時(shí)候有一個(gè)需求就是，好友搜索功能。即在EditText中輸入好友名字，ListView列表中動(dòng)態(tài)展示刷選的好友列表。我把這個(gè)功能抽取出來(lái)了，先貼一下效果圖：
分析
在查閱資料以后，發(fā)現(xiàn)其實(shí)Android中已經(jīng)幫我們實(shí)現(xiàn)了這個(gè)功能，如果你的ListView使用的是系統(tǒng)的ArrayAdapter，那么恭喜你，下面的事情就很簡(jiǎn)單了，你只需要調(diào)用下面的代碼就可以實(shí)現(xiàn)了：
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) { // }});你沒(méi)看錯(cuò)，就一行 mAdapter.getFilter().filter(cs);便可以實(shí)現(xiàn)這個(gè)搜索功能。不過(guò)我相信大多數(shù)Adapter都是自定義的，基于這個(gè)需求，我去分析了下ArrayAdapter，發(fā)現(xiàn)它實(shí)現(xiàn)了Filterable接口，那么接下來(lái)的事情就比較簡(jiǎn)單了，就讓我們自定的Adapter也去實(shí)現(xiàn)Filterable這個(gè)接口，不久可以實(shí)現(xiàn)這個(gè)需求了嗎。下面貼出ArrayAdapter中顯示過(guò)濾功能的關(guān)鍵代碼：
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(); } } }}實(shí)現(xiàn)
首先寫(xiě)了一個(gè)Model（User）模擬數(shù)據(jù)
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; }}自定義一個(gè)Adapter（UserAdapter）繼承自BaseAdapter，實(shí)現(xiàn)了Filterable接口，Adapter一些常見(jiàn)的處理，我都去掉了，這里主要講講Filterable這個(gè)接口。
/** * Contains the list of objects that represent the data of this Adapter. * Adapter數(shù)據(jù)源 */ private List<User> mDatas; //過(guò)濾相關(guān) /** * This lock is also used by the filter * (see {@link #getFilter()} to make a synchronized copy of * the original array of data. * 過(guò)濾器上的鎖可以同步復(fù)制原始數(shù)據(jù)。 * */ 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. //對(duì)象數(shù)組的備份，當(dāng)調(diào)用ArrayFilter的時(shí)候初始化和使用。此時(shí)，對(duì)象數(shù)組只包含已經(jīng)過(guò)濾的數(shù)據(jù)。 private ArrayList<User> mOriginalValues; private ArrayFilter mFilter; @Override public Filter getFilter() { if (mFilter == null) { mFilter = new ArrayFilter(); } return mFilter; }寫(xiě)一個(gè)ArrayFilter類繼承自Filter類，我們需要兩個(gè)方法：
//執(zhí)行過(guò)濾的方法 protected FilterResults performFiltering(CharSequence prefix);
//得到過(guò)濾結(jié)果 protected void publishResults(CharSequence prefix, FilterResults results);
貼上完整的代碼，注釋已經(jīng)寫(xiě)的不能再詳細(xì)了
/** * 過(guò)濾數(shù)據(jù)的類 */ /** * <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/> * 一個(gè)帶有首字母約束的數(shù)組過(guò)濾器，每一項(xiàng)不是以該首字母開(kāi)頭的都會(huì)被移除該list。 */ private class ArrayFilter extends Filter { //執(zhí)行刷選 @Override protected FilterResults performFiltering(CharSequence prefix) { FilterResults results = new FilterResults();//過(guò)濾的結(jié)果 //原始數(shù)據(jù)備份為空時(shí)，上鎖，同步復(fù)制原始數(shù)據(jù) if (mOriginalValues == null) { synchronized (mLock) { mOriginalValues = new ArrayList<>(mDatas); } } //當(dāng)首字母為空時(shí) if (prefix == null || prefix.length() == 0) { ArrayList<User> list; synchronized (mLock) {//同步復(fù)制一個(gè)原始備份數(shù)據(jù) list = new ArrayList<>(mOriginalValues); } results.values = list; results.count = list.size();//此時(shí)返回的results就是原始的數(shù)據(jù)，不進(jìn)行過(guò)濾 } else { String prefixString = prefix.toString().toLowerCase();//轉(zhuǎn)化為小寫(xiě) ArrayList<User> values; synchronized (mLock) {//同步復(fù)制一個(gè)原始備份數(shù)據(jù) 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);//從List<User>中拿到User對(duì)象// final String valueText = value.toString().toLowerCase(); final String valueText = value.getName().toString().toLowerCase();//User對(duì)象的name屬性作為過(guò)濾的參數(shù) // First match against the whole, non-splitted value if (valueText.startsWith(prefixString) || valueText.indexOf(prefixString.toString()) != -1) {//第一個(gè)字符是否匹配 newValues.add(value);//將這個(gè)item加入到數(shù)組對(duì)象中 } else {//處理首字符是空格 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循環(huán) newValues.add(value); break; } } } } results.values = newValues;//此時(shí)的results就是過(guò)濾后的List<User>數(shù)組 results.count = newValues.size(); } return results; } //刷選結(jié)果 @Override protected void publishResults(CharSequence prefix, FilterResults results) { //noinspection unchecked mDatas = (List<User>) results.values;//此時(shí)，Adapter數(shù)據(jù)源就是過(guò)濾后的Results if (results.count > 0) { notifyDataSetChanged();//這個(gè)相當(dāng)于從mDatas中刪除了一些數(shù)據(jù)，只是數(shù)據(jù)的變化，故使用notifyDataSetChanged() } else { /** * 數(shù)據(jù)容器變化 ----> notifyDataSetInValidated 容器中的數(shù)據(jù)變化 ----> notifyDataSetChanged */ notifyDataSetInvalidated();//當(dāng)results.count<=0時(shí)，此時(shí)數(shù)據(jù)源就是重新new出來(lái)的，說(shuō)明原始的數(shù)據(jù)源已經(jīng)失效了 } } }特別說(shuō)明
//User對(duì)象的name屬性作為過(guò)濾的參數(shù) final String valueText = value.getName().toString().toLowerCase();
這個(gè)地方是，你要進(jìn)行搜索的關(guān)鍵字，比如我這里使用的是User對(duì)象的Name屬性，就是把用戶名當(dāng)作關(guān)鍵字來(lái)進(jìn)行過(guò)濾篩選的。這里要根據(jù)你自己的具體邏輯來(lái)進(jìn)行設(shè)置。
在這里進(jìn)行關(guān)鍵字匹配，如果你只想使用第一個(gè)字符匹配，那么你只需要使用這行代碼就可以了：
//首字符匹配valueText.startsWith(prefixString)
如果你的需求是只要輸入的字符出現(xiàn)在ListView列表中，那么該item就要顯示出來(lái)，那么你就需要這行代碼了：
//你輸入的關(guān)鍵字包含在了某個(gè)item中，位置不做考慮，即可以不是第一個(gè)字符 valueText.indexOf(prefixString.toString()) != -1
這樣就完成了一個(gè)EditText + ListView實(shí)現(xiàn)搜索的功能。我在demo中用兩種方法實(shí)現(xiàn)了這一效果。第一種是系統(tǒng)的ArrayAdapter實(shí)現(xiàn)，第二種是自定義Adapter實(shí)現(xiàn)。
demo下載地址：EditSearch_jb51.rar
以上就是本文的全部?jī)?nèi)容，希望對(duì)大家的學(xué)習(xí)有所幫助，也希望大家多多支持武林網(wǎng)。
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