Android四大组件——ContentProvider的增删改查和优化

ContentProvider的增删改查和优化

事先说明：

ContentProvider步骤：创数据库，写规则匹配，配置manifests，另一个应用使用

其实ContentProvider就是：在一个匹配器中写入自己写好的匹配规则，并对外提供写好的匹配规则供使用，剩下的就是增删改查的处理

细节处理：

在增删改查中的查询中，是没有cursor.getBoolean这个方法的，所以要对数据库中获取布尔值进行处理：

msg.setFlag(cursor.getInt(cursor.getColumnIndex("flag")) != 0);

ContentProvider的增删改查

步骤一：创建一个类继承SQLiteOpenHelper，并用SQL语句创建一个SQLite

    public class CommonOpenHelper extends SQLiteOpenHelper {    private static CommonOpenHelper helper;    public static CommonOpenHelper getInstance(Context context) {        if (helper == null) {            helper = new CommonOpenHelper(context, "common.db", null, 1);        }        return helper;    }    private CommonOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory, int version) {        super(context, name, factory, version);    }    @Override    public void onCreate(SQLiteDatabase db) {        db.execSQL("create table message(" +                "id integer primary key autoincrement, " +                "content varchar, " +                "date varchar " +                ")");    }    @Override    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {    }}

步骤二：创建一个类继承ContentProvider，提供增删改查的方法

    public class MyMessageProvider extends ContentProvider {    //数据库名    public final static String DB_MESSAGE = "message";    //放置一个数据库    CommonOpenHelper helper;    SQLiteDatabase db;    //空白匹配器    UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);    //自身的匹配规则    final static int CODE_MESSAGE_INSERT = 0;    final static int CODE_MESSAGE_QUERY = 1;    final static int CODE_MESSAGE_DELETE = 2;    final static int CODE_MESSAGE_UPDATE = 3;    //主机名    final static String authority = "com.handsome.nfcc";    final static Uri BASE_URI = Uri.parse("content://com.handsome.nfcc");        //写入该主机名的匹配规则    {        matcher.addURI(authority, "message/insert", CODE_MESSAGE_INSERT);        matcher.addURI(authority, "message/query", CODE_MESSAGE_QUERY);        matcher.addURI(authority, "message/delete", CODE_MESSAGE_DELETE);        matcher.addURI(authority, "message/update", CODE_MESSAGE_UPDATE);    }    //对外提供的URI    public interface URI {        Uri CODE_MESSAGE_INSERT = Uri.parse("content://" + authority + "/message/insert");        Uri CODE_MESSAGE_QUERY = Uri.parse("content://" + authority + "/message/query");        Uri CODE_MESSAGE_DELETE = Uri.parse("content://" + authority + "/message/delete");        Uri CODE_MESSAGE_UPDATE = Uri.parse("content://" + authority + "/message/update");    }    @Override    public boolean onCreate() {        helper = CommonOpenHelper.getInstance(getContext());        db = helper.getWritableDatabase();        return false;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {        switch (matcher.match(uri)) {            case CODE_MESSAGE_QUERY:                Cursor cursor = db.query(DB_MESSAGE, projection, selection, selectionArgs, null, null, sortOrder);                //注册内容观察者，观察数据变化                cursor.setNotificationUri(getContext().getContentResolver(), BASE_URI);                return cursor;            default:                throw new IllegalArgumentException("未识别的uri" + uri);        }    }    @Override    public String getType(Uri uri) {        return null;    }    @Override    public Uri insert(Uri uri, ContentValues values) {        switch (matcher.match(uri)) {            case CODE_MESSAGE_INSERT:                long rowId = db.insert(DB_MESSAGE, null, values);                if (rowId == -1) {                    //添加失败                    return null;                } else {                    //发送内容广播                    getContext().getContentResolver().notifyChange(BASE_URI, null);                    //添加成功                    return ContentUris.withAppendedId(uri, rowId);                }            default:                throw new IllegalArgumentException("未识别的uri" + uri);        }    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        switch (matcher.match(uri)) {            case CODE_MESSAGE_DELETE:                int number = db.delete(DB_MESSAGE, selection, selectionArgs);                //发送内容广播                getContext().getContentResolver().notifyChange(BASE_URI, null);                return number;            default:                throw new IllegalArgumentException("未识别的uri" + uri);        }    }    @Override    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {        switch (matcher.match(uri)) {            case CODE_MESSAGE_UPDATE:                int number = db.update(DB_MESSAGE, values, selection, selectionArgs);                //发送内容广播                getContext().getContentResolver().notifyChange(BASE_URI, null);                return number;            default:                throw new IllegalArgumentException("未识别的uri" + uri);        }    }}

步骤三：在manifests文件中配置你所写的ContentProvider

    <provider            android:name=".Provider.MyMessageProvider"            android:authorities="com.handsome.nfcc" />

步骤四：在另一个应用中写一个数据库的增删改查类，使用该ContentProvider

    public class MessageDao {    /**     * 添加数据     */    public static boolean insert(ContentResolver resolver, Message msg) {        ContentValues values = new ContentValues();        values.put("content", msg.getContent());        values.put("date", DateUtils.showDate());        resolver.insert(MyMessageProvider.URI.CODE_MESSAGE_INSERT, values);        return true;    }    /**     * 删除数据     */    public static void delete(ContentResolver resolver, int id) {        resolver.delete(MyMessageProvider.URI.CODE_MESSAGE_DELETE, "id = " + id, null);    }    /**     * 删除全部数据     */    public static void deleteAll(ContentResolver resolver) {        resolver.delete(MyMessageProvider.URI.CODE_MESSAGE_DELETE, null, null);    }    /**     * 查询数据     *     * @param resolver     * @return     */    public static List<Message> query(ContentResolver resolver) {        List<Message> list = new ArrayList<>();        Cursor cursor = resolver.query(MyMessageProvider.URI.CODE_MESSAGE_QUERY, null, null, null, null);        while (cursor.moveToNext()) {            Message msg = new Message();            msg.setDate(cursor.getString(cursor.getColumnIndex("date")));            msg.setContent(cursor.getString(cursor.getColumnIndex("content")));            msg.setId(cursor.getInt(cursor.getColumnIndex("id")));            list.add(0, msg);        }        return list;    }}

ContentProvider的优化

往往在一个项目中有很多的数据库，这个时候并不是重复的写ContentProvider代码，而是将所有数据库中放在一个ContentProvider中，提供一个查询表名的方法，并对其相应的表进行操作

步骤一：ContentProvider的代码优化（一套代码适用多个数据库）

public class MyDataProvider extends ContentProvider {    //数据库名    public final static String DB_DATA = "data";    public final static String DB_FETCH = "fetch";    public final static String DB_MESSAGE = "message";    //放置一个数据库    CommonOpenHelper helper;    SQLiteDatabase db;    UriMatcher matcher = new UriMatcher(UriMatcher.NO_MATCH);    //自身的匹配规则    final static int CODE_DATA = 0;    final static int CODE_FETCH = 1;    final static int CODE_MESSAGE = 2;    //主机名    final static String authority = "com.handsome.nfc";    final static Uri BASE_URI = Uri.parse("content://com.handsome.nfc");    //写入该主机名的匹配规则    {        matcher.addURI(authority, "data", CODE_DATA);        matcher.addURI(authority, "fetch", CODE_FETCH);        matcher.addURI(authority, "message", CODE_MESSAGE);    }    //对外提供的URI    public interface URI {        Uri DATA_CONTENT_URI = Uri.parse(BASE_URI + "/data");        Uri FETCH_CONTENT_URI = Uri.parse(BASE_URI + "/fetch");        Uri MESSAGE_CONTENT_URI = Uri.parse(BASE_URI + "/message");    }    /**     * 获取数据库表名     *     * @param uri     * @return     */    private String getTableName(Uri uri) {        String tableName = null;        switch (matcher.match(uri)) {            case CODE_DATA:                tableName = DB_DATA;                break;            case CODE_FETCH:                tableName = DB_FETCH;                break;            case CODE_MESSAGE:                tableName = DB_MESSAGE;                break;            default:                break;        }        return tableName;    }    @Override    public boolean onCreate() {        helper = CommonOpenHelper.getInstance(getContext());        db = helper.getWritableDatabase();        return false;    }    @Override    public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {        String tableName = getTableName(uri);        if (tableName == null) {            throw new IllegalArgumentException("非法Uri：" + uri);        }        Cursor cursor = db.query(tableName, projection, selection, selectionArgs, null, null, sortOrder);        //注册内容观察者，观察数据变化        cursor.setNotificationUri(getContext().getContentResolver(), BASE_URI);        return cursor;    }    @Override    public String getType(Uri uri) {        return null;    }    @Override    public Uri insert(Uri uri, ContentValues values) {        String tableName = getTableName(uri);        if (tableName == null) {            throw new IllegalArgumentException("非法Uri：" + uri);        }        long rowId = db.insert(tableName, null, values);        if (rowId == -1) {            return null;        } else {            //发送内容广播            getContext().getContentResolver().notifyChange(BASE_URI, null);            return ContentUris.withAppendedId(uri, rowId);        }    }    @Override    public int delete(Uri uri, String selection, String[] selectionArgs) {        String tableName = getTableName(uri);        if (tableName == null) {            throw new IllegalArgumentException("非法Uri：" + uri);        }        int number = db.delete(tableName, selection, selectionArgs);        //发送内容广播        getContext().getContentResolver().notifyChange(BASE_URI, null);        return number;    }    @Override    public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {        String tableName = getTableName(uri);        if (tableName == null) {            throw new IllegalArgumentException("非法Uri：" + uri);        }        int number = db.update(tableName, values, selection, selectionArgs);        //发送内容广播        getContext().getContentResolver().notifyChange(BASE_URI, null);        return number;    }}

步骤二：在各个不同的数据库中的使用

Data数据库通过名字查询示例

private static boolean queryDataByName(ContentResolver resolver, String tag_id) {        Cursor cursor = resolver.query(MyDataProvider.URI.DATA_CONTENT_URI, null, "tag_id = '" + tag_id + "'", null, null);        if (cursor.moveToFirst()) {            return true;        }        return false;    }

Fetch数据库插入示例

public static boolean insert(ContentResolver resolver, Fetch fetch) {        ContentValues values = new ContentValues();        values.put("fetch_num", fetch.getFetch_num());        values.put("username", fetch.getUsername());        values.put("installationId", fetch.getInstallationId());        values.put("created", fetch.getCreated());        values.put("date", System.currentTimeMillis());        resolver.insert(MyDataProvider.URI.FETCH_CONTENT_URI, values);        return true;    }

Message数据库查询示例

 public static List<Message> query(ContentResolver resolver) {        List<Message> list = new ArrayList<>();        Cursor cursor = resolver.query(MyDataProvider.URI.MESSAGE_CONTENT_URI, null, null, null, null);        while (cursor.moveToNext()) {            Message msg = new Message();            msg.setDate(cursor.getString(cursor.getColumnIndex("date")));            msg.setContent(cursor.getString(cursor.getColumnIndex("content")));            msg.setId(cursor.getInt(cursor.getColumnIndex("id")));            list.add(0, msg);        }        return list;    }