5MI/NotesProvider.java

/*
 * Copyright (c) 2010-2011, The MiCode Open Source Community (www.micode.net)
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *        http://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package net.micode.notes.data;

import android.app.SearchManager;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.content.Intent;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;

import net.micode.notes.R;
import net.micode.notes.data.Notes.DataColumns;
import net.micode.notes.data.Notes.NoteColumns;
import net.micode.notes.data.NotesDatabaseHelper.TABLE;

// 主要的 NotesProvider 类，继承自 ContentProvider
public class NotesProvider extends ContentProvider {
    private static final UriMatcher mMatcher; // URI匹配器

    private NotesDatabaseHelper mHelper; // 数据库帮助类

    private static final String TAG = "NotesProvider"; // 日志标签

    // 定义URI匹配码
    private static final int URI_NOTE            = 1;
    private static final int URI_NOTE_ITEM       = 2;
    private static final int URI_DATA            = 3;
    private static final int URI_DATA_ITEM       = 4;

    private static final int URI_SEARCH          = 5;
    private static final int URI_SEARCH_SUGGEST  = 6;

    // 初始化URI匹配器
    static {
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        mMatcher.addURI(Notes.AUTHORITY, "note", URI_NOTE);
        mMatcher.addURI(Notes.AUTHORITY, "note/#", URI_NOTE_ITEM);
        mMatcher.addURI(Notes.AUTHORITY, "data", URI_DATA);
        mMatcher.addURI(Notes.AUTHORITY, "data/#", URI_DATA_ITEM);
        mMatcher.addURI(Notes.AUTHORITY, "search", URI_SEARCH);
        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, URI_SEARCH_SUGGEST);
        mMatcher.addURI(Notes.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", URI_SEARCH_SUGGEST);
    }

    // 定义搜索时使用的投影
    /**
     * x'0A' represents the '\n' character in sqlite. For title and content in the search result,
     * we will trim '\n' and white space in order to show more information.
     */
    private static final String NOTES_SEARCH_PROJECTION = NoteColumns.ID + ","
        + NoteColumns.ID + " AS " + SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA + ","
        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_1 + ","
        + "TRIM(REPLACE(" + NoteColumns.SNIPPET + ", x'0A','')) AS " + SearchManager.SUGGEST_COLUMN_TEXT_2 + ","
        + R.drawable.search_result + " AS " + SearchManager.SUGGEST_COLUMN_ICON_1 + ","
        + "'" + Intent.ACTION_VIEW + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_ACTION + ","
        + "'" + Notes.TextNote.CONTENT_TYPE + "' AS " + SearchManager.SUGGEST_COLUMN_INTENT_DATA;

    // 定义搜索查询
    private static String NOTES_SNIPPET_SEARCH_QUERY = "SELECT " + NOTES_SEARCH_PROJECTION
        + " FROM " + TABLE.NOTE
        + " WHERE " + NoteColumns.SNIPPET + " LIKE ?"
        + " AND " + NoteColumns.PARENT_ID + "<>" + Notes.ID_TRASH_FOLER
        + " AND " + NoteColumns.TYPE + "=" + Notes.TYPE_NOTE;

    @Override
    public boolean onCreate() {
        mHelper = NotesDatabaseHelper.getInstance(getContext()); // 获取数据库帮助类的实例
        return true;
    }

    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
            String sortOrder) {
        Cursor c = null;
        SQLiteDatabase db = mHelper.getReadableDatabase(); // 获取可读数据库
        String id = null;
        switch (mMatcher.match(uri)) { // 匹配URI
            case URI_NOTE:
                c = db.query(TABLE.NOTE, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_NOTE_ITEM:
                id = uri.getPathSegments().get(1); // 获取路径中的ID
                c = db.query(TABLE.NOTE, projection, NoteColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            case URI_DATA:
                c = db.query(TABLE.DATA, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            case URI_DATA_ITEM:
                id = uri.getPathSegments().get(1); // 获取路径中的ID
                c = db.query(TABLE.DATA, projection, DataColumns.ID + "=" + id
                        + parseSelection(selection), selectionArgs, null, null, sortOrder);
                break;
            case URI_SEARCH:
            case URI_SEARCH_SUGGEST:
                if (sortOrder != null || projection != null) {
                    throw new IllegalArgumentException(
                            "do not specify sortOrder, selection, selectionArgs, or projection" + "with this query");
                }

                String searchString = null;
                if (mMatcher.match(uri) == URI_SEARCH_SUGGEST) {
                    if (uri.getPathSegments().size() > 1) {
                        searchString = uri.getPathSegments().get(1);
                    }
                } else {
                    searchString = uri.getQueryParameter("pattern");
                }

                if (TextUtils.isEmpty(searchString)) {
                    return null;
                }

                try {
                    searchString = String.format("%%%s%%", searchString);
                    c = db.rawQuery(NOTES_SNIPPET_SEARCH_QUERY,
                            new String[] { searchString });
                } catch (IllegalStateException ex) {
                    Log.e(TAG, "got exception: " + ex.toString());
                }
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        if (c != null) {
            c.setNotificationUri(getContext().getContentResolver(), uri); // 设置通知URI
        }
        return c;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        SQLiteDatabase db = mHelper.getWritableDatabase(); // 获取可写数据库
        long dataId = 0, noteId = 0, insertedId = 0;
        switch (mMatcher.match(uri)) { // 匹配URI
            case URI_NOTE:
                insertedId = noteId = db.insert(TABLE.NOTE, null, values); // 插入笔记
                break;
            case URI_DATA:
                if (values.containsKey(DataColumns.NOTE_ID)) {
                    noteId = values.getAsLong(DataColumns.NOTE_ID); // 获取笔记ID
                } else {
                    Log.d(TAG, "Wrong data format without note id:" + values.toString());
                }
                insertedId = dataId = db.insert(TABLE.DATA, null, values); // 插入数据
                break;
            default:
                throw new IllegalArgumentException("Unknown URI " + uri);
        }
        // Notify the note uri
        if (noteId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_NOTE_URI, noteId), null);
        }

        // Notify the data uri
        if (dataId > 0) {
            getContext().getContentResolver().notifyChange(
                    ContentUris.withAppendedId(Notes.CONTENT_DATA_URI, dataId), null);
        }

        return ContentUris.withAppendedId(uri, insertedId); // 返回插入的URI
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int count = 0;
        String id = null;
        SQLiteDatabase db = mHelper.getWritableDatabase(); // 获取可写数据库
        boolean deleteData = false;
        switch (mMatcher.match(uri)) { // 匹配URI
            case URI_NOTE:
                selection = "(" + selection + ") AND " + NoteColumns.ID + ">0 "; // 确保ID大于0
                count = db.delete(TABLE.NOTE, selection, selectionArgs); // 删除笔记
                break;
            case URI_NOTE_ITEM:
                id = uri.getPathSegments().get(1); // 获取路径中的ID
                /**
                 * ID that smaller than 0 is system folder which is not allowed to
                 * trash
                 */
                long noteId = Long.valueOf(id);
                if (noteId <= 0) {
                    break;
                }
                count = db.delete(TABLE.NOTE,
                        NoteColumns.ID + "=" +id + parseSelection(selection), selectionArgs); // 删除笔记项
					break;
			case URI_DATA:
				count = db.delete(TABLE.DATA, selection, selectionArgs); // 删除数据
				deleteData = true;
					break;
			case URI_DATA_ITEM:
				id = uri.getPathSegments().get(1); // 获取路径中的ID
				count = db.delete(TABLE.DATA,
				DataColumns.ID + "=" + id + parseSelection(selection), selectionArgs); // 删除数据项
				deleteData = true;
				break;
			default:
				throw new IllegalArgumentException("Unknown URI " + uri);
		}
	if (count > 0) {
		if (deleteData) {
			getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null); // 通知删除数据
		}
		getContext().getContentResolver().notifyChange(uri, null); // 通知删除
	}		
	return count;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
    int count = 0;
    String id = null;
    SQLiteDatabase db = mHelper.getWritableDatabase(); // 获取可写数据库
    boolean updateData = false;
    switch (mMatcher.match(uri)) { // 匹配URI
        case URI_NOTE:
            increaseNoteVersion(-1, selection, selectionArgs); // 增加笔记版本
            count = db.update(TABLE.NOTE, values, selection, selectionArgs); // 更新笔记
            break;
        case URI_NOTE_ITEM:
            id = uri.getPathSegments().get(1); // 获取路径中的ID
            increaseNoteVersion(Long.valueOf(id), selection, selectionArgs); // 增加笔记版本
            count = db.update(TABLE.NOTE, values, NoteColumns.ID + "=" + id
                    + parseSelection(selection), selectionArgs); // 更新笔记项
            break;
        case URI_DATA:
            count = db.update(TABLE.DATA, values, selection, selectionArgs); // 更新数据
            updateData = true;
            break;
        case URI_DATA_ITEM:
            id = uri.getPathSegments().get(1); // 获取路径中的ID
            count = db.update(TABLE.DATA, values, DataColumns.ID + "=" + id
                    + parseSelection(selection), selectionArgs); // 更新数据项
            updateData = true;
            break;
        default:
            throw new IllegalArgumentException("Unknown URI " + uri);
    }

    if (count > 0) {
        if (updateData) {
            getContext().getContentResolver().notifyChange(Notes.CONTENT_NOTE_URI, null); // 通知更新数据
        }
        getContext().getContentResolver().notifyChange(uri, null); // 通知更新
    }
    return count;
}

private String parseSelection(String selection) {
    return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : ""); // 解析选择条件
}

private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
    StringBuilder sql = new StringBuilder(120);
    sql.append("UPDATE ");
    sql.append(TABLE.NOTE);
    sql.append(" SET ");
    sql.append(NoteColumns.VERSION);
    sql.append("=" + NoteColumns.VERSION + "+1 ");

    if (id > 0 || !TextUtils.isEmpty(selection)) {
        sql.append(" WHERE ");
    }
    if (id > 0) {
        sql.append(NoteColumns.ID + "=" + String.valueOf(id));
    }
    if (!TextUtils.isEmpty(selection)) {
        String selectString = id > 0 ? parseSelection(selection) : selection;
        for (String args : selectionArgs) {
            selectString = selectString.replaceFirst("\\?", args);
        }
        sql.append(selectString);
    }

    mHelper.getWritableDatabase().execSQL(sql.toString()); // 执行更新SQL
}

@Override
public String getType(Uri uri) {
    // TODO Auto-generated method stub
    return null;
}