ContentProvider数据共享

创建数据库

创建一个类放置ContentProvider会用到的列名

创建ContentProvider的子类

定义URI

在Manifest的XML中添加android:authorities属性与URI一致

定义MIME类型

package d.m;import android.net.Uri;/** * @version 2012-7-17 上午11:10:12 **/public final class table {    private table() {    }    // 数据路径 与Manifest.xml中android:authorities的值相同    public static String AUTHORITY = "d.m.dbname";    // 列名    public static final String KEY_ID = "_id";    public static final String KEY_NAME = "name";    public static final String KEY_NUM = "num";    // URI 固定格式 content://+数据路径+标示ID(可选)    public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY);    // 新的MIME类型-多个    public static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.google.note";    // 新的MIME类型-单个    public static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.google.note";}

package d.m;import java.util.HashMap;import android.content.ContentProvider;import android.content.ContentUris;import android.content.ContentValues;import android.content.UriMatcher;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteQueryBuilder;import android.net.Uri;import android.text.TextUtils;/** * @version 2012-7-17 上午11:27:09 **/public class cp extends ContentProvider {    // 标示使用UriMatcher匹配的标示ID    private static final int TB = 1;    private static final int TB_ID = 2;    private DatabaseHelper databaseHelper;    // 用于匹配Uri    private static final UriMatcher MATCHER;    // 设置    private static HashMap<String, String> projectMap;    static {        projectMap = new HashMap<String, String>();        projectMap.put(table.KEY_ID, table.KEY_ID);        projectMap.put(table.KEY_NAME, table.KEY_NAME);        projectMap.put(table.KEY_NUM, table.KEY_NUM);        // 常量UriMatcher.NO_MATCH表示不匹配任何路径的返回码(-1)。        MATCHER = new UriMatcher(UriMatcher.NO_MATCH);        // 如果match()方法匹配AUTHORITY的值加上/TB 则返回1        MATCHER.addURI(table.AUTHORITY, "tb", TB);        // 如果match()方法匹配AUTHORITY的值加上/TB/数字 则返回2        MATCHER.addURI(table.AUTHORITY, "tb/#", TB_ID);        // 加*标示任意字符    }    /*     * 每当ContentProvider启动时都会回调onCreate()方法。此方法主要执行一些ContentProvider初始化     * 的工作，返回true表示初始化成功，返回false则初始化失败。     */    @Override    public boolean onCreate() {        databaseHelper = new DatabaseHelper(getContext());        return true;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection,            String[] selectionArgs, String sortOrder) {        SQLiteQueryBuilder qb = new SQLiteQueryBuilder();        switch(MATCHER.match(uri)) {            case TB:                qb.setTables(DatabaseHelper.DB_TABLE);                qb.setProjectionMap(projectMap);                break;            case TB_ID:                qb.setTables(DatabaseHelper.DB_TABLE);                qb.setProjectionMap(projectMap);                qb.appendWhere(table.KEY_ID + "="                        + uri.getPathSegments().get(1));                // uri.getPathSegments().get(1)用来获得URI中的参数                break;        }        SQLiteDatabase db = databaseHelper.getReadableDatabase();        Cursor c = qb.query(db, projection, selection, selectionArgs, null,                null, sortOrder);        c.setNotificationUri(getContext().getContentResolver(), uri);        return c;    }    @Override    public String getType(Uri uri) {        switch(MATCHER.match(uri)) {            case TB:                return table.CONTENT_TYPE;            case TB_ID:                return table.CONTENT_ITEM_TYPE;            default:                throw new IllegalArgumentException("Unknow URI " + uri);        }     }    @Override    public Uri insert(Uri uri, ContentValues values) {        switch(MATCHER.match(uri)) {            case TB:                ContentValues v2 = new ContentValues(values);                // 判断是否存在该值                if(!v2.containsKey(table.KEY_NAME)) {                    values.put(table.KEY_NAME, "def_name");                }                if(!v2.containsKey(table.KEY_NUM)) {                    values.put(table.KEY_NUM, "def_num");                }                SQLiteDatabase db = databaseHelper.getWritableDatabase();                // 返回行ID                long rowId = db.insert(databaseHelper.DB_TABLE, table.KEY_NAME,                        values);                if(rowId > 0) {                    // 生成一个URI content://d.m.dbname/tb/1                    Uri noteUri = ContentUris.withAppendedId(                            Uri.parse("content://" + table.AUTHORITY + "/tb"),                            rowId);                    // 监听数据库的程序发一个通知                    getContext().getContentResolver().notifyChange(noteUri,                            null);                    return noteUri;                }                break;        }        return null;    }    @Override    // 删除数据    public int delete(Uri uri, String where, String[] whereArgs) {        SQLiteDatabase db = databaseHelper.getWritableDatabase();        int count;        switch(MATCHER.match(uri)) {            case TB:                count = db.delete(DatabaseHelper.DB_TABLE, where, whereArgs);                break;            case TB_ID:                String noteId = uri.getPathSegments().get(1);                count = db.delete(DatabaseHelper.DB_TABLE, table.KEY_ID                        + "="                        + noteId                        + (!TextUtils.isEmpty(where) ? " AND (" + where + ')'                                : ""), whereArgs);                break;            default:                throw new IllegalArgumentException("Unknown URI " + uri);        }        // 监听数据库的程序发一个通知        getContext().getContentResolver().notifyChange(uri, null);        return count;    }    @Override    // 更新数据    public int update(Uri uri, ContentValues values, String where,            String[] whereArgs) {        SQLiteDatabase db = databaseHelper.getWritableDatabase();        int count;        switch(MATCHER.match(uri)) {            case TB:                count = db.update(DatabaseHelper.DB_TABLE, values, where,                        whereArgs);                break;            case TB_ID:                String noteId = uri.getPathSegments().get(1);                count = db.update(DatabaseHelper.DB_TABLE, values, table.KEY_ID                        + "="                        + noteId                        + (!TextUtils.isEmpty(where) ? " AND (" + where + ')'                                : ""), whereArgs);                break;            default:                throw new IllegalArgumentException("Unknown URI " + uri);        }        // 监听数据库的程序发一个通知        getContext().getContentResolver().notifyChange(uri, null);        return count;    }}