前段时间介绍了大致获取搜索联想词的步骤, 这次我们介绍一下获取网络联想词的详细步骤, 我们知道 获取网络

联想词是通过SearchEngine实现的, 在浏览器中, 实现有两套方案:

1. OpenSearchEngine会去定制的服务器获取搜索的联想词 

2. DefaultSearchEngine 使用Android内部的SearchManager去query 联想列表

但是无论如何返回的数据是Cursor 并返回给SuggestCursor 

下面详细分析一下 首先是OpenSearchSearchEngine 的初始化: 初始化了 HttpClent

 public OpenSearchSearchEngine(Context context, SearchEngineInfo searchEngineInfo) {        mSearchEngineInfo = searchEngineInfo;        mHttpClient = AndroidHttpClient.newInstance(USER_AGENT);//设置了UA        HttpParams params = mHttpClient.getParams();         params.setLongParameter(HTTP_TIMEOUT, HTTP_TIMEOUT_MS);//设置超时    }

在SlowFilterTask这个Task中开始query

class SlowFilterTask extends AsyncTask
    
     
      > {        @Override        protected List
      
        doInBackground(CharSequence... params) {            SuggestCursor cursor = new SuggestCursor();            cursor.runQuery(params[0]);//开始query            List
       
         results = new ArrayList
        
         ();            int count = cursor.getCount();//遍历Cursor中的各个数据            for (int i = 0; i < count; i++) {                results.add(cursor.getItem());                cursor.moveToNext();            }            cursor.close();            return results;        }        @Override        protected void onPostExecute(List
         
           items) {            mSuggestResults = items;            mMixedResults = buildSuggestionResults();//获取数据成功了把数据混合然后更新UI            notifyDataSetChanged();        }    }
         
        
       
      
     
    

在SuggestCursor的runQuery中调用 SearchEngine  的 getSuggestions函数

 /**     * Queries for a given search term and returns a cursor containing     * suggestions ordered by best match.     */    public Cursor getSuggestions(Context context, String query) {        if (TextUtils.isEmpty(query)) {            return null;        }        if (!isNetworkConnected(context)) {//检查网络是否ok            Log.i(TAG, "Not connected to network.");            return null;        }        String suggestUri = mSearchEngineInfo.getSuggestUriForQuery(query); //从什么搜索引擎搜索联想词        if (TextUtils.isEmpty(suggestUri)) {            // No suggest URI available for this engine            return null;        }        try {            String content = readUrl(suggestUri); //从网络获取联想词            if (content == null) return null;            /* The data format is a JSON array with items being regular strings or JSON arrays             * themselves. We are interested in the second and third elements, both of which             * should be JSON arrays. The second element/array contains the suggestions and the             * third element contains the descriptions. Some search engines don't support             * suggestion descriptions so the third element is optional.             */            JSONArray results = new JSONArray(content); //返回的是Json            JSONArray suggestions = results.getJSONArray(1);            JSONArray descriptions = null;            if (results.length() > 2) {                descriptions = results.getJSONArray(2);                // Some search engines given an empty array "[]" for descriptions instead of                // not including it in the response.                if (descriptions.length() == 0) {                    descriptions = null;                }            }            return new SuggestionsCursor(suggestions, descriptions); //返回这个Json        } catch (JSONException e) {            Log.w(TAG, "Error", e);        }        return null;    }

从网络获取数据代码

 /**     * Executes a GET request and returns the response content.     *     * @param url Request URI.     * @return The response content. This is the empty string if the response     *         contained no content.     */    public String readUrl(String url) {        try {            HttpGet method = new HttpGet(url);            HttpResponse response = mHttpClient.execute(method);            if (response.getStatusLine().getStatusCode() == 200) {                return EntityUtils.toString(response.getEntity());            } else {                Log.i(TAG, "Suggestion request failed");                return null;            }        } catch (IOException e) {            Log.w(TAG, "Error", e);            return null;        }    }

SuggestionsCursor 继承自AbstractCursor 也是一个Cursor了

private static class SuggestionsCursor extends AbstractCursor {        private final JSONArray mSuggestions;        private final JSONArray mDescriptions;        public SuggestionsCursor(JSONArray suggestions, JSONArray descriptions) {            mSuggestions = suggestions;            mDescriptions = descriptions;        }        @Override        public int getCount() { //用来配合 moveToNext            return mSuggestions.length();        }        @Override        public String[] getColumnNames() {            return (mDescriptions != null ? COLUMNS : COLUMNS_WITHOUT_DESCRIPTION);        }        @Override        public String getString(int column) {             if (mPos != -1) {                if ((column == COLUMN_INDEX_QUERY) || (column == COLUMN_INDEX_TEXT_1)) {                    try {                        return mSuggestions.getString(mPos);                    } catch (JSONException e) {                        Log.w(TAG, "Error", e);                    }                } else if (column == COLUMN_INDEX_TEXT_2) {                    try {                        return mDescriptions.getString(mPos);                    } catch (JSONException e) {                        Log.w(TAG, "Error", e);                    }                } else if (column == COLUMN_INDEX_ICON) {                    return String.valueOf(R.drawable.magnifying_glass);                }            }            return null;        }        @Override        public double getDouble(int column) {            throw new UnsupportedOperationException();        }        @Override        public float getFloat(int column) {            throw new UnsupportedOperationException();        }        @Override        public int getInt(int column) {            throw new UnsupportedOperationException();        }        @Override        public long getLong(int column) {            if (column == COLUMN_INDEX_ID) {                return mPos;        // use row# as the _Id            }            throw new UnsupportedOperationException();        }        @Override        public short getShort(int column) {            throw new UnsupportedOperationException();        }        @Override        public boolean isNull(int column) {            throw new UnsupportedOperationException();        }    }

这里废话一句AbstractCursor重要的函数 moveToFirst是如何使用getCount的 在AbstractCursor.java中

参考代码 http://code.taobao.org/p/cnandroiddocs/src/trunk/core/java/android/database/AbstractCursor.java

 public final boolean moveToPosition(int position) {        // Make sure position isn't past the end of the cursor        final int count = getCount();        if (position >= count) {            mPos = count;            return false;        }        // Make sure position isn't before the beginning of the cursor        if (position < 0) {            mPos = -1;            return false;        }        // Check for no-op moves, and skip the rest of the work for them        if (position == mPos) {            return true;        }        boolean result = onMove(mPos, position);        if (result == false) {            mPos = -1;        } else {            mPos = position;            if (mRowIdColumnIndex != -1) {                mCurrentRowID = Long.valueOf(getLong(mRowIdColumnIndex));            }        }        return result;    }    @Override    public void fillWindow(int position, CursorWindow window) {        DatabaseUtils.cursorFillWindow(this, position, window);    }    public final boolean move(int offset) {        return moveToPosition(mPos + offset);    }    public final boolean moveToFirst() {        return moveToPosition(0);    }

既然返回了SuggestCursor SuggestionAdapter就可以拿到Cursor进行 数据的读取了

 class SuggestCursor extends CursorSource {        @Override        public SuggestItem getItem() {//读取SuggestionsCursor中的数据            if (mCursor != null) {                String title = mCursor.getString(                         mCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_TEXT_1));                String text2 = mCursor.getString(                        mCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_TEXT_2));                String url = mCursor.getString(                        mCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_TEXT_2_URL));                String uri = mCursor.getString(                        mCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_INTENT_DATA));                int type = (TextUtils.isEmpty(url)) ? TYPE_SUGGEST : TYPE_SUGGEST_URL;                SuggestItem item = new SuggestItem(title, url, type);                item.extra = mCursor.getString(                        mCursor.getColumnIndex(SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA));                return item;            }            return null;        }        @Override        public void runQuery(CharSequence constraint) {            if (mCursor != null) {                mCursor.close();            }            //这里拿到的是OpenSearchSearchEngine对象,后面在分析            SearchEngine searchEngine = mSettings.getSearchEngine();            if (!TextUtils.isEmpty(constraint)) {                if (searchEngine != null && searchEngine.supportsSuggestions()) {                	//最后拿到的是json 然后返回一个cursor对象 操作json用来做混合 联想词 处理                	//json居然可以这样用! 自定义Cursor , Cursor不仅仅可以用来存取数据库数据                    mCursor = searchEngine.getSuggestions(mContext, constraint.toString());                    if (mCursor != null) {                        mCursor.moveToFirst();                     }                }            } else {                if (searchEngine.wantsEmptyQuery()) {                    mCursor = searchEngine.getSuggestions(mContext, "");                }                mCursor = null;            }        }    }