Content Providers-----浅析

一

自定义ContentProvider

步骤:1.创建一个类,继承Contentprovider

2.实现所有的抽象方法;onCreate()

getType()

query()

update()

delete()

ContentResolver对象调用的query() 、insert() 、update()、delete() 就是 ContentProvider类中的重写后的query() 、insert() 、update()、delete() 方法。

3.定义ContentProvider的Uri,

4. UriMatcher matcher=new UriMatcher(UriMatcher.NO_MATCH);

静态代码块  static{

		//添加要 匹配的URI
<span style="white-space:pre">		</span>参数1：authority   
<span style="white-space:pre">		</span>参数2：资源路径：表名      
<span style="white-space:pre">		</span>参数3：该uri匹配成功的返回码code
		//完整路径Uri：content://com.example.day17demo01provider.db.StuProvider/javaScore
 
<span style="white-space:pre">		</span>matcher.addURI(AUTHORITY, DBHelper.TABLE_NAME, 1);
		
		//模糊匹配：id--->#数值
		
<span style="white-space:pre">		</span>matcher.addURI(AUTHORITY, DBHelper.TABLE_NAME+"/#", 2);
		
		//模糊匹配：name---》*文本
		matcher.addURI(AUTHORITY, DBHelper.TABLE_NAME+"/*", 3);		

}

	//实例化ContentProvider的时候调用---》不要做耗时操作
	@Override
	public boolean onCreate() {
		db=new DBHelper(getContext()).getWritableDatabase();
		return false;
	}
//查找数据--->查找SQLite---》SQLiteDataBase
	//参数1：uri    参数2：要查找的列    参数4：查找条件     参数5：条件中占位符的值   参数6：排序
	@Override
	public Cursor query(Uri uri, String[] projection, String selection,
			String[] selectionArgs, String sortOrder) {
		//把传进来的uri进行匹配---》定位一条数据还是多条数据
		int code = matcher.match(uri);
		
		Cursor cursor = null;
		
		switch (code) {
		case 1://全部
			cursor = db.query(DBHelper.TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
			break;
		case 2://指定id
			//取出uri中的id
			long id = ContentUris.parseId(uri);
			
			cursor = db.query(DBHelper.TABLE_NAME, projection, DBHelper.JAVA_ID+" = ?", new String[]{id+""}, null, null, sortOrder);
			break;
		case 3://指定name
			//取出name值
			String name=uri.getLastPathSegment();
			//查找条件---》name的值--》模糊匹配
			cursor=db.query(DBHelper.TABLE_NAME, projection, " name like '%"+name+"%'", null, null, null, sortOrder);
			
			break;
		default:
			break;
		}
		return cursor;
	}
	//获取类型--->name、没有值匹配---》1、3---》多条数据
	//2：单条数据
	@Override
	public String getType(Uri uri) {
		String type=null;
		
		int code = matcher.match(uri);
		switch (code) {
		case 1://多条数据
		case 3:
			type="vnd.android.cursor.dir/vnd."+AUTHORITY+"."+DBHelper.TABLE_NAME;
			break;
			
		case 2:
			type="vnd.android.cursor.item/vnd."+AUTHORITY+"."+DBHelper.TABLE_NAME;

			break;

		default:
			break;
		}
		
		return type;
	}
	//插入数据
	@Override
	public Uri insert(Uri uri, ContentValues values) {
		int code = matcher.match(uri);
		Uri withAppendedId =null;
		if(code==1){
			long id = db.insert(DBHelper.TABLE_NAME, null, values);
			
			withAppendedId = ContentUris.withAppendedId(uri, id);
		}
		return withAppendedId;
	}
	//删除
	@Override
	public int delete(Uri uri, String selection, String[] selectionArgs) {
		int rawNum =0;
		
		int code = matcher.match(uri);
		
		if(code==2){//包含有数值--》id
			long id = ContentUris.parseId(uri);//删除条件
			
			//数据库的删除操作
			rawNum = db.delete(DBHelper.TABLE_NAME, DBHelper.JAVA_ID+" = ?", new String[]{id+""});
		}
		
		return rawNum;
	}
	//更新
	@Override
	public int update(Uri uri, ContentValues values, String selection,
			String[] selectionArgs) {
		
		int code = matcher.match(uri);
		switch (code) {
		case 1://没有指定name、id
			db.update(DBHelper.TABLE_NAME, values, selection, selectionArgs);
			break;
		case 2://id
			//取出id
			long id = ContentUris.parseId(uri);
			
			//根据id去更新数
			db.update(DBHelper.TABLE_NAME, values, DBHelper.JAVA_ID+" = ?", new String[]{id+""});
			break;
		case 3://name
			//取出name
			String name = uri.getLastPathSegment();
			//根据name去更新
			db.update(DBHelper.TABLE_NAME, values, DBHelper.JAVA_NAME+" like '%"+name+"%'", null);
			
			break;


		default:
			break;
		}
		
		return 0;
	}

}