Android ContentProvider的双重用途:1.搜索提供商和2.列出内容提供程序

Question

1. 我有一个ContentProvider，它抽象了我用于填充列表CursorAdapter的信息。

2. 我正在操作栏中构建一个SearchView，并希望向其附加搜索ContentProvider。 我可以为此使用相同的提供程序吗？这是好的设计吗？SearchView内容将与#1相同，它仅用于搜索大量的项目列表视图。

ContentProvider代码如下：

public class WebSitesContentProvider extends ContentProvider {
    // database
    private UserDatabaseHelper database;
    // Used for the UriMacher
    private static final int TOTAL_ELEMENTS = 10;
    private static final int ELEMENT_ID = 20;
    private static final String BASE_PATH = "websites";
    public static final Uri CONTENT_URI = Uri.parse("content://" + Consts.AUTHORITY + "/" + BASE_PATH);
    public static final String CONTENT_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE + "/website";
    public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE + Consts.TABLE_WEBSITES_INFO;
    private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    static {
        sURIMatcher.addURI(Consts.AUTHORITY, BASE_PATH, TOTAL_ELEMENTS);
        sURIMatcher.addURI(Consts.AUTHORITY, BASE_PATH + "/#", ELEMENT_ID);
    }
    @Override
    public boolean onCreate() {
        database = new UserDatabaseHelper(getContext());
        return false;
    }
    @Override
    public String getType(Uri uri) {
        return null;
    }
    @Override
    public Cursor query(Uri uri, String[] projection, String selection,
            String[] selectionArgs, String sortOrder) {
        // UsIng SQLiteQueryBuilder instead of query() method
        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
        // Check if the caller has requested a column which does not exists
        checkColumns(projection);
        // Set the table
        queryBuilder.setTables(Consts.TABLE_WEBSITES_INFO);
        int uriType = sURIMatcher.match(uri);
        switch (uriType) {
        case TOTAL_ELEMENTS:
            break;
        case ELEMENT_ID:
            // Adding the ID to the original query
            queryBuilder.appendWhere(Consts.COLUMN_ID + "=" + uri.getLastPathSegment());
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        SQLiteDatabase db = database.getWritableDatabase();
        Cursor cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder);
        // Make sure that potential listeners are getting notified
        cursor.setNotificationUri(getContext().getContentResolver(), uri);
        return cursor;
    }
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        int uriType = sURIMatcher.match(uri);
        SQLiteDatabase sqlDB = database.getWritableDatabase();
        int rowsDeleted = 0;
        long id = 0;
        switch (uriType) {
        case TOTAL_ELEMENTS:
            id = sqlDB.insert(Consts.TABLE_WEBSITES_INFO, null, values);
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return Uri.parse(BASE_PATH + "/" + id);
    }
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int uriType = sURIMatcher.match(uri);
        SQLiteDatabase sqlDB = database.getWritableDatabase();
        int rowsDeleted = 0;
        switch (uriType) {
        case TOTAL_ELEMENTS:
            rowsDeleted = sqlDB.delete(Consts.TABLE_WEBSITES_INFO,
                    selection,
                    selectionArgs);
            break;
        case ELEMENT_ID:
            String id = uri.getLastPathSegment();
            if (TextUtils.isEmpty(selection)) {
                rowsDeleted = sqlDB.delete(Consts.TABLE_WEBSITES_INFO,
                        Consts.COLUMN_ID + "=" + id,
                        null);
            } else {
                rowsDeleted = sqlDB.delete(Consts.TABLE_WEBSITES_INFO,
                        Consts.COLUMN_ID + "=" + id + " and " + selection,
                        selectionArgs);
            }
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        /*
         * Let's not notify content observers on deletes of less then 1 as each delete would cause a network call.
         * user could delete multiple entries at once. if the deletes are greater then 1 then it's probably a 
         * request to remove the entire list, this we will allow
         */
        //if(rowsDeleted>1)
            getContext().getContentResolver().notifyChange(uri, null);
        return rowsDeleted;
    }
    @Override
    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
        int uriType = sURIMatcher.match(uri);
        SQLiteDatabase sqlDB = database.getWritableDatabase();
        int rowsUpdated = 0;
        switch (uriType) {
        case TOTAL_ELEMENTS:
            rowsUpdated = sqlDB.update(Consts.TABLE_WEBSITES_INFO, 
                    values, 
                    selection,
                    selectionArgs);
            break;
        case ELEMENT_ID:
            String id = uri.getLastPathSegment();
            if (TextUtils.isEmpty(selection)) {
                rowsUpdated = sqlDB.update(Consts.TABLE_WEBSITES_INFO, 
                        values,
                        Consts.COLUMN_ID + "=" + id, 
                        null);
            } else {
                rowsUpdated = sqlDB.update(Consts.TABLE_WEBSITES_INFO, 
                        values,
                        Consts.COLUMN_ID + "=" + id + " and " + selection,
                        selectionArgs);
            }
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return rowsUpdated;
    }
    private void checkColumns(String[] projection) {
        String[] available = {
                Consts.COLUMN_USER,
                Consts.COLUMN_ID
        };
        if (projection != null) {
            HashSet<String> requestedColumns = new HashSet<String>(Arrays.asList(projection));
            HashSet<String> availableColumns = new HashSet<String>(Arrays.asList(available));
            // Check if all columns which are requested are available
            if (!availableColumns.containsAll(requestedColumns)) {
                throw new IllegalArgumentException("Unknown columns in projection");
            }
        }
    }
}

更新

ContentProvider是通用的，我同意这一点。它们可以进行调整。所以我调整了我的来处理SearchView数据内容。

以下是整个ContentProvider，它既是SearchView内容提供商，又是ListView光标适配器，供任何感兴趣的人使用：

package org.jefferyemanuel.database;
import java.util.Arrays;
import java.util.HashSet;
import org.jefferyemanuel.bulkwebsites.Consts;
import org.jefferyemanuel.bulkwebsites.Utils;
import android.app.SearchManager;
import android.content.ContentProvider;
import android.content.ContentResolver;
import android.content.ContentValues;
import android.content.UriMatcher;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteQueryBuilder;
import android.net.Uri;
import android.provider.BaseColumns;
import android.text.TextUtils;
import android.util.Log;
public class WebSitesContentProvider extends ContentProvider {
    /* define out search provider structures */
    // UriMatcher constant for search suggestions
    private static final int SEARCH_SUGGEST = 1;
    private static final String[] SEARCH_SUGGEST_COLUMNS = {
            BaseColumns._ID,
            SearchManager.SUGGEST_COLUMN_TEXT_1,
            SearchManager.SUGGEST_COLUMN_INTENT_DATA,
            SearchManager.SUGGEST_COLUMN_INTENT_EXTRA_DATA,
            SearchManager.SUGGEST_COLUMN_SHORTCUT_ID
    };
    // database
    private UserDatabaseHelper database;
    // Used for the UriMacher
    private static final int TOTAL_ELEMENTS = 10;
    private static final int ELEMENT_ID = 20;
    private static final String BASE_PATH = "websites";
    public static final Uri CONTENT_URI = Uri.parse("content://" + Consts.AUTHORITY + "/" + BASE_PATH);
    public static final String CONTENT_TYPE = ContentResolver.CURSOR_DIR_BASE_TYPE + "/website";
    public static final String CONTENT_ITEM_TYPE = ContentResolver.CURSOR_ITEM_BASE_TYPE + Consts.TABLE_WEBSITES_INFO;
    private static final UriMatcher sURIMatcher = new UriMatcher(UriMatcher.NO_MATCH);
    static {
        sURIMatcher.addURI(Consts.AUTHORITY, BASE_PATH, TOTAL_ELEMENTS);
        sURIMatcher.addURI(Consts.AUTHORITY, BASE_PATH + "/#", ELEMENT_ID);
        sURIMatcher.addURI(Consts.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY, SEARCH_SUGGEST);
        sURIMatcher.addURI(Consts.AUTHORITY, SearchManager.SUGGEST_URI_PATH_QUERY + "/*", SEARCH_SUGGEST);
    }
    @Override
    public boolean onCreate() {
        database = new UserDatabaseHelper(getContext());
        return false;
    }
    @Override
    public String getType(Uri uri) {
        return null;
    }
    @Override
    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
        // UsIng SQLiteQueryBuilder instead of query() method
        SQLiteQueryBuilder queryBuilder = new SQLiteQueryBuilder();
        // Check if the caller has requested a column which does not exists
        checkColumns(projection);
        // Set the table
        queryBuilder.setTables(Consts.TABLE_WEBSITES_INFO);
        int uriType = sURIMatcher.match(uri);
        switch (uriType) {
        case TOTAL_ELEMENTS:
            break;
        case SEARCH_SUGGEST:
            queryBuilder.appendWhere(Consts.COLUMN_NAME + " LIKE '%" + uri.getLastPathSegment() + "%'");
            break;
        case ELEMENT_ID:
            // Adding the ID to the original query
            queryBuilder.appendWhere(Consts.COLUMN_ID + "=" + uri.getLastPathSegment());
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        SQLiteDatabase db = database.getWritableDatabase();
        Cursor cursor = queryBuilder.query(db, projection, selection, selectionArgs, null, null, sortOrder);
        /*
         * If this request is from a SearchView then convert cursor to search Matrix cursor.
         */
        if (uriType == SEARCH_SUGGEST)
            cursor = buildSearchMatrixCursorFromStandardCursor(cursor);
        // Make sure that potential listeners are getting notified
        cursor.setNotificationUri(getContext().getContentResolver(), uri);
        return cursor;
    }
    @Override
    public Uri insert(Uri uri, ContentValues values) {
        int uriType = sURIMatcher.match(uri);
        SQLiteDatabase sqlDB = database.getWritableDatabase();
        int rowsDeleted = 0;
        long id = 0;
        switch (uriType) {
        case TOTAL_ELEMENTS:
            id = sqlDB.insert(Consts.TABLE_WEBSITES_INFO, null, values);
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return Uri.parse(BASE_PATH + "/" + id);
    }
    @Override
    public int delete(Uri uri, String selection, String[] selectionArgs) {
        int uriType = sURIMatcher.match(uri);
        SQLiteDatabase sqlDB = database.getWritableDatabase();
        int rowsDeleted = 0;
        switch (uriType) {
        case TOTAL_ELEMENTS:
            rowsDeleted = sqlDB.delete(Consts.TABLE_WEBSITES_INFO, selection, selectionArgs);
            break;
        case ELEMENT_ID:
            String id = uri.getLastPathSegment();
            if (TextUtils.isEmpty(selection)) {
                rowsDeleted = sqlDB.delete(Consts.TABLE_WEBSITES_INFO,
                        Consts.COLUMN_ID + "=" + id,
                        null);
            } else {
                rowsDeleted = sqlDB.delete(Consts.TABLE_WEBSITES_INFO,
                        Consts.COLUMN_ID + "=" + id + " and " + selection,
                        selectionArgs);
            }
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return rowsDeleted;
    }
    @Override
    public int update(Uri uri, ContentValues values, String selection,
            String[] selectionArgs) {
        int uriType = sURIMatcher.match(uri);
        SQLiteDatabase sqlDB = database.getWritableDatabase();
        int rowsUpdated = 0;
        switch (uriType) {
        case TOTAL_ELEMENTS:
            rowsUpdated = sqlDB.update(Consts.TABLE_WEBSITES_INFO, values,
                    selection, selectionArgs);
            break;
        case ELEMENT_ID:
            String id = uri.getLastPathSegment();
            if (TextUtils.isEmpty(selection)) {
                rowsUpdated = sqlDB.update(Consts.TABLE_WEBSITES_INFO, values,
                        Consts.COLUMN_ID + "=" + id,
                        null);
            } else {
                rowsUpdated = sqlDB.update(Consts.TABLE_WEBSITES_INFO, values,
                        Consts.COLUMN_ID + "=" + id + " and " + selection,
                        selectionArgs);
            }
            break;
        default:
            throw new IllegalArgumentException("Unknown URI: " + uri);
        }
        getContext().getContentResolver().notifyChange(uri, null);
        return rowsUpdated;
    }
    private void checkColumns(String[] projection) {
        String[] available = { Consts.COLUMN_NAME, Consts.COLUMN_ID };
        if (projection != null) {
            HashSet<String> requestedColumns = new HashSet<String>(Arrays.asList(projection));
            HashSet<String> availableColumns = new HashSet<String>(Arrays.asList(available));
            // Check if all columns which are requested are available
            if (!availableColumns.containsAll(requestedColumns)) {
                throw new IllegalArgumentException("Unknown columns in projection");
            }
        }
    }
    /*
     * KEY METHOD THAT USES THE DATA FROM DATABASE THAT LISTVIEW ALSO USES 
     * TO CREATE A MATRIX CURSOR TO SEND BACK TO SEARCHVIEW
     */
    private Cursor buildSearchMatrixCursorFromStandardCursor(Cursor cursor) {
        MatrixCursor cursorSearch = new MatrixCursor(SEARCH_SUGGEST_COLUMNS);
        int id = 0;
        int index = cursor.getColumnIndex(Consts.COLUMN_NAME);
        cursor.moveToFirst();
        while (!cursor.isAfterLast()) {
            String name = cursor.getString(index);
            cursorSearch.addRow(new String[] {
                    String.valueOf(++id),
                    name,
                    name,
                    name,
                    SearchManager.SUGGEST_NEVER_MAKE_SHORTCUT
            });
            cursor.moveToNext();
        }
        return cursorSearch;
    }
}

Answer 1

您正在使用的内容提供程序是通用的，可用于搜索功能。

起初你可能会想，也许你应该写一个专门用于搜索的内容提供程序，但是：

• 您将不得不复制大量代码。
• 内容提供者不是为了具体而设计的，它们只是抽象了对数据的访问。

您的"搜索内容提供商"将用于进行查询，并且您已经拥有内容提供商。

内容提供程序不需要特定于搜索。另一方面，您的助手应该是具体的。