group12/doc/卢冠铮精读/NotesProvider.java

import android.content.ContentProvider;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.net.Uri;
import android.text.TextUtils;
import android.util.Log;
import android.app.SearchManager;
import net.micode.notes.data.Notes;

// 定义 NotesProvider 类
public class NotesProvider extends ContentProvider {
    // UriMatcher 用于匹配 Uri
    private static final UriMatcher mMatcher;
    private NotesDatabaseHelper mHelper;
    private static final String TAG = "NotesProvider";
    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;

    static {
        // 创建 UriMatcher 时，调用 UriMatcher(UriMatcher.NO_MATCH) 表示不匹配任何路径的返回码
        mMatcher = new UriMatcher(UriMatcher.NO_MATCH);
        // 把需要匹配 Uri 路径全部给注册上
        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);
    }

    // 声明 NOTES_SEARCH_PROJECTION
    private static final String NOTES_SEARCH_PROJECTION = "……";
    // 声明 NOTES_SNIPPET_SEARCH_QUERY
    private static String NOTES_SNIPPET_SEARCH_QUERY = "……";

    // 定义 mHelper 初始化方法
    @Override
    public boolean onCreate() {
        mHelper = NotesDatabaseHelper.getInstance(getContext());
        return true;
    }

    @Override
    // 查询 uri 在数据库中对应的位置
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs,
                        String sortOrder) {
        Cursor c = null;
        // 获取可读数据库
        SQLiteDatabase db = mHelper.getReadableDatabase();
        String id = null;
        // 匹配查找 uri
        switch (mMatcher.match(uri)) {
            // 对于不同的匹配值，在数据库中查找相应的条目
            case URI_NOTE:
                c = db.query(NotesDatabaseHelper.TABLE.NOTE, projection, selection, selectionArgs, null, null,
                        sortOrder);
                break;
            // 这里省略原代码中 query 方法里的省略部分
            case URI_SEARCH_SUGGEST:
                if (sortOrder != null || projection != null) {
                    // 不合法的参数异常
                    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) {
                        // getPathSegments() 方法得到一个 String 的 List，
                        // 在 uri.getPathSegments().get(1) 为第 2 个元素
                        searchString = uri.getPathSegments().get(1);
                    }
                }
                // 这里省略原代码中 case URI_SEARCH_SUGGEST 里的省略部分
                break;
        }
        return c;
    }

    // 将字符串解析成规定格式
    private String parseSelection(String selection) {
        return (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
    }

    // 更新一个 uri
    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        int count = 0;
        String id = null;
        SQLiteDatabase db = mHelper.getWritableDatabase();
        boolean updateData = false;
        // 这里省略原代码中 update 方法里的省略部分
        return count;
    }

    // 增加一个 noteVersion
    private void increaseNoteVersion(long id, String selection, String[] selectionArgs) {
        StringBuilder sql = new StringBuilder(120);
        sql.append("UPDATE ");
        sql.append(NotesDatabaseHelper.TABLE.NOTE);
        sql.append(" SET ");
        sql.append(Notes.NoteColumns.VERSION);
        sql.append("=" + Notes.NoteColumns.VERSION + "+1 ");
        if (id > 0 || !TextUtils.isEmpty(selection)) {
            sql.append(" WHERE ");
        }
        if (id > 0) {
            sql.append(Notes.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);
        }
        // execSQL() 方法可以执行 insert、delete、update 和 CREATE TABLE 之类有更改行为的 SQL 语句
        mHelper.getWritableDatabase().execSQL(sql.toString());
    }

    @Override
    public String getType(Uri uri) {
        return null;
    }

    @Override
    public Uri insert(Uri uri, ContentValues values) {
        // 这里可以添加插入数据的逻辑
        return null;
    }

    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        // 这里可以添加删除数据的逻辑
        return 0;
    }
}