{"id":92,"date":"2015-11-11T10:36:44","date_gmt":"2015-11-11T10:36:44","guid":{"rendered":"https:\/\/boochlin.com\/?p=92"},"modified":"2016-07-13T14:34:28","modified_gmt":"2016-07-13T14:34:28","slug":"android-orm-library-green-dao%ef%bc%88%e4%ba%8c%ef%bc%89question-why-cant-set-default-value-for-entities","status":"publish","type":"post","link":"https:\/\/boochlin.com\/?p=92","title":{"rendered":"Android ORM Library – Green DAO\uff08\u4e8c\uff09Question: Why can’t set default value for entities"},"content":{"rendered":"

Question: Why no set default value for entities<\/h3>\n

\u5176\u5be6\u4e00\u958b\u59cb\u6a19\u984c\u4e0d\u662f\u9019\u6a23\uff0c\u800c\u662f some tips\uff0c\u4f46\u662f\u5149\u662f\u804a\u7b2c\u4e00\u500b\u554f\u984c\u5c31\u5169\u5343\u591a\u5b57\uff0c\u6240\u4ee5\u4e7e\u8106\u5207\u51fa\u4e00\u500b\u65b0\u7684\u3002\u53e6\u5916\u5efa\u8b70\u5148\u770b\u7b2c\u4e00\u7bc7<\/a>\uff0c\u6216\u662f\u5df2\u7d93\u6709\u76f8\u95dc\u77e5\u8b58<\/p>\n

topic\uff1aWhy can’t set default value for entities<\/strong><\/p>\n

Question:<\/h3>\n

\u70ba\u4f55 GreenDAO\u00a0\u5728\u5efa\u7acbEntity\u968e\u6bb5\u6c92\u6709\u8fa6\u6cd5\u5c0d\u6bcf\u500b property \u8a2d\u5b9a\u521d\u503c\uff1f<\/strong><\/p>\n

\u7d50\u679c\u5c31\u662f\u4ee5\u4e0b\u7684 code \u7121\u6cd5\u7528GreenDAO generator \u7684\u76f8\u95dc method \u81ea\u52d5\u7522\u751f\u51fa\u4f86\u3002\u539f\u56e0\u51fa\u5728 DEFAULT -1 \u9019\u6558\u8ff0\u53e5\u6c92\u8fa6\u6cd5\u81ea\u52d5\u7522\u751f\u3002<\/p>\n

db.execSQL(\"CREATE TABLE \" + constraint + \"'LeftPage' (\" + \/\/\r\n        \"'DATA_ID' INTEGER PRIMARY KEY ,\" + \/\/ 0: DataID\r\n        \"'CATEGORY' TEXT NOT NULL ,\" + \/\/ 1: Category\r\n        \"'PROVIDER' TEXT,\" + \/\/ 2: Provider\r\n        \"'DISPLAY_ORDER' INTEGER DEFAULT -1\uff09\uff09;\"); \/\/ 3: DisplayOrder<\/pre>\n
\u9019\u554f\u984c\u7576\u7136\u4e0d\u53ea\u6211\u4e00\u500b\u4eba\u60f3\u5230\uff0c\u7562\u7adf Default value \u5e7e\u4e4e\u662f sql \u7684\u8d77\u624b\u5f0f\u3002
\n\u96a8\u4fbf\u6536\u96c6\u4e00\u4e0b
\n \u89e3\u51b3android greenDAO\u6ca1\u6709\u9ed8\u8ba4\u503cdefault value\u548c\u6ca1\u6709\u539f\u59cb\u6570\u636e\u7c7b\u578b\u7684\u95ee\u9898<\/a>
\nAndroid – add default value in GreenDao database<\/a>
\nAdding default values for entities<\/a>
\n\u6839\u64da\u4e0a\u9762\uff0c\u751a\u81f3\u51fa\u73fe\u8981\u6c42\u4f5c\u8005\u52a0\u5165\u6b64\u529f\u80fd\u7684\u9023\u7f72\u8072\u97f3
\nDefault Values for Entity Properties<\/a><\/p>\n
<\/p>\n
\u901a\u5e38\u6709\u95dc sqlite script \u7684\u9019\u6bb5\u5275\u5efa table \u7684 code \u662f\u7531GreenDAO\u00a0generator \u5728\u8a2d\u5b9a Entity \u5f8c\u81ea\u52d5\u5efa\u51fa\u4f86\u7684\uff1a\u5982\u4e0b<\/p>\n
Entity commonData = schema.addEntity(\"CommonData\");\r\ncommonData.setTableName(\"LeftPage\");\r\n\/\/commonData.addContentProvider();\r\n\r\ncommonData.addLongProperty(\"DataID\").primaryKey();\r\ncommonData.addStringProperty(\"Category\");\r\ncommonData.addStringProperty(\"Provider\");\r\ncommonData.addIntProperty(\"DisplayOrder\");<\/pre>\n
\u524d\u9762\u6240\u6709\u7684\u6b04\u4f4dname , primary key , data type\u00a0\u90fd\u53ef\u4ee5\u5728\u5efa\u5236 Entity \u6642\u6307\u5b9a\u597d\uff0c\u552f\u4e00\u7684\u907a\u61be\u5c31\u662f\u70ba\u4f55\u4e0d\u80fd\u5728\u9019\u968e\u6bb5\u52a0\u5165 DEFAULT value \u9032\u800c\u53bb\u5f71\u97ffGreenDAO\u00a0generator \u7522\u751f\u7684 sql create table script code \uff0c\u505a\u500b\u985e\u4f3c\u7684api \u4e0d\u5c31\u641e\u5b9a\u4e86 \u50cf\u662f\uff1asetDefaultValue(String xxx) or DefaultValue(int xxx) \u3002
\n\u76f8\u4fe1\u9019\u7d55\u5c0d\u4e0d\u96e3 \u89e3\u51b3android greenDAO\u6ca1\u6709\u9ed8\u8ba4\u503cdefault value\u548c\u6ca1\u6709\u539f\u59cb\u6570\u636e\u7c7b\u578b\u7684\u95ee\u9898<\/a>\u9019\u4f4d\u5927\u5927\u5c31\u81ea\u5df1\u641e\u4e86\u4e00\u5957\uff0c\u5982\u679c\u770b\u5b98\u78ba\u5be6\u60f3\u8981\u9019\u6a23\u7684\u529f\u80fd\u7684\u8a71\uff0c\u8acb\u81ea\u53d6\u3002
\n\u5982\u679c\u61f6\u5f97\u62ff\u5c31\u76f4\u63a5\u4fee\u6539 xxxDao.java \u88e1\u9762\u7684 sql script\uff08\u50cf\u6700\u4e0a\u9762\u9019\u6bb5code\uff09 , \u9019\u6a23\u6700\u5feb<\/p>\n
\u90a3\u67d0\u6211\u5c31\u60f3\u77e5\u9053\u70ba\u4f55GreenDAO\u00a0\u958b\u767c\u8005\u70ba\u4f55\u4e0d\u5c0e\u5165\u9019\u6a23\u7684\u529f\u80fd\uff0c\u800c\u4e14\u770b\u8d77\u4f862012 \u5c31\u6709\u4eba\u5728\u558a\u9019\u4ef6\u4e8b\uff0c\u4f46\u662f\u4f5c\u8005\u9084\u662f\u4e0d\u641e<\/strong>
\n\u4ee5\u4e0b\u958b\u59cb\u5c31\u662f\u500b\u4eba\u898b\u89e3\uff0c\u8aaa\u4e0d\u5b9a\u6709\u9ede\u5f37\u89e3\u4f5c\u8005\u610f\u5716 \u300e\u70ba\u4f55GreenDAO\u00a0\u4e0d\u8b93\u4f7f\u7528\u8005\u53ef\u4ee5\u81ea\u7531\u8a2d\u5b9a default value \uff1f<\/span>\u300f<\/p>\n
\u62c6\u6210\u5e7e\u500b\u6b65\u9a5f\u4f86\u770b\u9019\u554f\u984c<\/p>\n
1. \u57fa\u672c\u4e0a\u53ea\u4fee\u6539 create table sqlite \u5c0dorm \u64cd\u4f5c\u4e26\u4e0d\u5b8c\u6574<\/strong>
\n\u7c21\u55ae\u4f86\u8aaa \u901a\u5e38\u5012\u5165orm \u5f8c\uff0cinsert \u901a\u5e38\u90fd\u6703\u662f\u4ee5 object \u70ba\u5c0d\u8c61\u9032\u884c\u64cd\u4f5c\uff0c\u800c\u975e\u662fContent value\uff0c\u6240\u4ee5\u7576\u4f60\u9032\u884c\u4ee5\u4e0b\u64cd\u4f5c\u6642<\/p>\n
CommonDataDao.insert(new CommonData());\r\n<\/pre>\n
\u7d50\u679c\u9810\u5b9a\u8981\u8a2d \u00a0default value \u00a0\u7684\u6b04\u4f4d\uff0c\u9084\u662f\u585e\u5165 null \u9032\u53bb\uff0c\u56e0\u70ba\u7576\u4f60new object \u6642\uff0c\u88e1\u9762\u7684\u6b04\u4f4d\u8b8a\u6578\u521d\u503c\u9084\u662fnull\uff0c\u4e0d\u7ba1type \u662f int\/double\/string \u90fd\u4e00\u6a23\uff0c\u56e0\u70ba object \u88e1\u9762\u7684\u6bcf\u4e00\u500b\u6b04\u4f4d\u4e26\u4e0d\u662f \u57fa\u672c\u8cc7\u6599\u578b\u985e\u5225(PRIMITIVE TYPE)\uff0c\u800c\u90fd\u662f \u5916\u5305\u985e\u5225(wrapper classes)\u3002<\/span>
\n \u9019\u9020\u6210\u4f60\u4e0d\u7279\u5225 assign \u7684\u8a71\u5c31\u662fnull , \u9023\u57fa\u672c\u8cc7\u6599\u578b\u985e\u5225\u7684\u521d\u503c\u90fd\u6c92\u6709<\/span>\uff1a\u7576\u7136\u5982\u679c\u662f\u7528 content value \u642d\u966acontent resolver\u9084\u662f\u6709\u7528\u7684\u3002\u4e0d\u904e\u90a3\u9019\u6a23\u7684\u8a71\u4f60\u5c31\u4e0d\u61c9\u8a72\u7528 orm \u963f<\/del><\/p>\n
2. \u90a3\u5c31\u5728 object \u88e1\u9762\u8a2d\u5b9a\u521d\u503c\u963f\uff0c\u6216\u8005\u7279\u5b9asetArg(int value);<\/strong>
\n\u76f4\u63a5\u53bb\u4fee\u6539CommonData.java\uff0c\u4f8b\u5982\uff1a\u5b9a\u7fa9\u6b04\u4f4d\u6642\u76f4\u63a5\u7d66\u503c<\/p>\n
    private String category;\r\n    private String mProvider;\r\n    private Integer DisplayOrder = -1;\r\n<\/pre>\n
\u770b\u8d77\u4f86\u5230\u9019\u908a\uff0c\u81f3\u5c11\u8655\u7406 insert \u662f\u5c0d\u7684<\/p>\n
    CommonDataDao.insert(new CommonData());\r\n<\/pre>\n
3. \u4f46\u662f\u5982\u679c\u63a5\u4e0b\u4f86\u662f\u8655\u7406update\u7684\u60c5\u6cc1\u5462\uff1f<\/strong><\/p>\n
    CommonData data = new CommonData();\r\n    data.setDataID(target_id);\r\n    CommonDataDao.update();\r\n<\/pre>\n
\u9019\u6703\u767c\u751f\u5565\u60c5\u6cc1\u5462\uff1f \u7531\u65bcupdate\u8cc7\u6599\u6642\u4e8b\u6839\u64da primary key \u4f5c\u70ba\u53d6\u4ee3\u76ee\u6a19\u7684 index<\/span>
\n \u6240\u4ee5\u4e00\u5b9a\u8981\u5148\u6307\u5b9a DataID \u4f5c\u70ba\u53d6\u4ee3\u76ee\u6a19\u7684id\uff0c\u4f46\u662f\u9019\u6b21update\u7684\u5c0d\u8c61\u88e1\u4e26\u6c92\u6709\u8981\u4fee\u6539 display order<\/span>
\n \u90a3\u67d0data \u7684 display order \u5c31\u6703\u7dad\u6301\u521d\u503c -1 \uff0c\u9032\u800c\u53bb\u66f4\u65b0 db \u7684\u90a3\u6b04\u8cc7\u6599\uff0c\u5f88\u660e\u986f\u9019\u6a23\u6703\u5f88\u7cdf\u7cd5\uff0c\u56e0\u70ba\u4f60\u5f04\u58de\u8cc7\u6599\u5eab\u5566\u3002<\/span><\/p>\n
\u5176\u5be6\u554f\u984c\u6c92\u90a3\u67d0\u5927\uff0c\u53ea\u8981\u8a18\u5f97 update \u4e4b\u524d\uff0cassign null to display order \u9032\u53bb\u5c31\u53ef\u4ee5\uff1a
\n\u6216\u8005\u6709\u4eba\u6703\u53cd\u99c1\uff0c\u901a\u5e38\u90fd\u662f\u5f9e db \u62ff\u51fa\u4f86\u5f8c\uff0c\u7136\u5f8c\u4fee\u6539\u5176\u4e2d\u5e7e\u9805\u5c31\u5728 update \u56de\u53bb<\/p>\n
\u6c92\u932f\uff0c\u9019\u6a23\u5c31\u6c92\u6709\u554f\u984c\u5566\uff0c\u751a\u81f3\u8aaa\u53ea\u8981\u958b\u767c\u8005\u5c0f\u5fc3\u4e00\u9ede\uff0c\u5c31\u4e00\u5207\u5b89\u5eb7<\/p>\n
\u5c0d\u65bcGreenDAO framework \u958b\u767c\u8005\u4f86\u8aaa\u7d55\u5c0d\u53ef\u4ee5\u5f88\u5feb\u7684\u628a setDefaultValue(int xxxx); \u7d66\u505a\u51fa\u4f86<\/span>
\n \u4f46\u662f\u4ed6\u6c92\u6709\u8fa6\u6cd5\u5728 framework \u5c64\u7d1a\u5e6b\u4f60\u8655\u7406\u6389\u5f8c\u7e8c\u6211\u4e0a\u9762\u63d0\u5230 side effect<\/span>
\n\u6700\u591a\u53ef\u4ee5\u5728insert \u6642 new CommonData() \u81ea\u52d5\u5e6b\u4f60\u52a0\u5165\u8a2d\u5b9a\u7684\u521d\u503c\uff0c\u4f46\u662f\u5f8c\u7e8c\u7684 update \u5927\u6982\u5c31\u6c92\u8fa6\u6cd5\u90a3\u67d0\u7c21\u55ae\u8655\u7406\u6389\uff08\u8aaa\u4e0d\u5b9a\u6709\u8fa6\u6cd5\uff0c\u4f46\u662f\u6211\u76ee\u524d\u60f3\u4e0d\u5230\uff09<\/span><\/p>\n
\u7c21\u55ae\u4f86\u8aaa\u5c31\u662f\u5f8c\u7e8c\u554f\u984c\u591a\u591a\u3002<\/span><\/strong><\/p>\n","protected":false},"excerpt":{"rendered":"
Question: Why no set default value for entities \u5176\u5be6\u4e00\u958b\u59cb\u6a19\u984c […]<\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[50,23],"tags":[6,53,9,24],"_links":{"self":[{"href":"https:\/\/boochlin.com\/index.php?rest_route=\/wp\/v2\/posts\/92"}],"collection":[{"href":"https:\/\/boochlin.com\/index.php?rest_route=\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/boochlin.com\/index.php?rest_route=\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/boochlin.com\/index.php?rest_route=\/wp\/v2\/users\/1"}],"replies":[{"embeddable":true,"href":"https:\/\/boochlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcomments&post=92"}],"version-history":[{"count":0,"href":"https:\/\/boochlin.com\/index.php?rest_route=\/wp\/v2\/posts\/92\/revisions"}],"wp:attachment":[{"href":"https:\/\/boochlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Fmedia&parent=92"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/boochlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Fcategories&post=92"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/boochlin.com\/index.php?rest_route=%2Fwp%2Fv2%2Ftags&post=92"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}