android 数据库之GreenDao使用

冷不防 2021-09-17 01:20 278阅读 0赞

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GreenDao

官方网站地址： [http://greenrobot.org/greendao/][http_greenrobot.org_greendao]

github地址     ： [https://github.com/greenrobot/greenDAO][https_github.com_greenrobot_greenDAO]

GreenDao 优点：

1 查询效率高

2 内存占用小

3 集成方便

使用方法:

1  引用（一个都不能少）

APP下的build.gradle

第一句一定不能忘！

apply plugin: 'org.greenrobot.greendao'//这句一定不能忘
    
    android {
       greendao {
                schemaVersion 1
                daoPackage 'com.tongyonghangkong.greendao.gen'//修改为gen文件实际位置，详情第二步
                targetGenDir 'src/main/java'
                }
    }
    
    dependencies {
       
        implementation 'org.greenrobot:greendao:3.1.0'
        implementation 'org.greenrobot:greendao-generator:3.1.0'
        implementation 'com.jakewharton:butterknife:8.1.0'
    
    }

project 下的build.gradle

两句标识 “这一句” 的一定不能忘

// Top-level build file where you can add configuration options common to all sub-projects/modules.
    
    buildscript {
        
        repositories {
            google()
            jcenter()
            mavenCentral()//这一句
        }
    
        dependencies {
            classpath 'com.android.tools.build:gradle:3.0.1'
            classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2'
            // NOTE: Do not place your application dependencies here; they belong
            // in the individual module build.gradle files
        }
    }
    
    allprojects {
        repositories {
            google()
            jcenter()
            maven{url "https://jitpack.io"}//这一句
        }
    }
    
    task clean(type: Delete) {
        delete rootProject.buildDir
    }

2 手动创建greendao.gen文件夹，用来存放被greenDao自动生成的代码

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3 初始化greenDao

首先要准备两个类： DaoMaster  DaoSession

package com.tongyonghangkong.greendao.gen;
    
    import android.content.Context;
    import android.database.sqlite.SQLiteDatabase;
    import android.database.sqlite.SQLiteDatabase.CursorFactory;
    import android.util.Log;
    
    import org.greenrobot.greendao.AbstractDaoMaster;
    import org.greenrobot.greendao.database.StandardDatabase;
    import org.greenrobot.greendao.database.Database;
    import org.greenrobot.greendao.database.DatabaseOpenHelper;
    import org.greenrobot.greendao.identityscope.IdentityScopeType;
    
    
    // THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT.
    /**
     * Master of DAO (schema version 1): knows all DAOs.
     */
    public class DaoMaster extends AbstractDaoMaster {
        public static final int SCHEMA_VERSION = 1;
    
        /** Creates underlying database table using DAOs. */
        public static void createAllTables(Database db, boolean ifNotExists) {
            ZhenHangDao.createTable(db, ifNotExists);
            WokersDao.createTable(db, ifNotExists);
        }
    
        /** Drops underlying database table using DAOs. */
        public static void dropAllTables(Database db, boolean ifExists) {
            ZhenHangDao.dropTable(db, ifExists);
            WokersDao.dropTable(db, ifExists);
        }
    
        /**
         * WARNING: Drops all table on Upgrade! Use only during development.
         * Convenience method using a {@link DevOpenHelper}.
         */
        public static DaoSession newDevSession(Context context, String name) {
            Database db = new DevOpenHelper(context, name).getWritableDb();
            DaoMaster daoMaster = new DaoMaster(db);
            return daoMaster.newSession();
        }
    
        public DaoMaster(SQLiteDatabase db) {
            this(new StandardDatabase(db));
        }
    
        public DaoMaster(Database db) {
            super(db, SCHEMA_VERSION);
            registerDaoClass(ZhenHangDao.class);
            registerDaoClass(WokersDao.class);
        }
    
        public DaoSession newSession() {
            return new DaoSession(db, IdentityScopeType.Session, daoConfigMap);
        }
    
        public DaoSession newSession(IdentityScopeType type) {
            return new DaoSession(db, type, daoConfigMap);
        }
    
        /**
         * Calls {@link #createAllTables(Database, boolean)} in {@link #onCreate(Database)} -
         */
        public static abstract class OpenHelper extends DatabaseOpenHelper {
            public OpenHelper(Context context, String name) {
                super(context, name, SCHEMA_VERSION);
            }
    
            public OpenHelper(Context context, String name, CursorFactory factory) {
                super(context, name, factory, SCHEMA_VERSION);
            }
    
            @Override
            public void onCreate(Database db) {
                Log.i("greenDAO", "Creating tables for schema version " + SCHEMA_VERSION);
                createAllTables(db, false);
            }
        }
    
        /** WARNING: Drops all table on Upgrade! Use only during development. */
        public static class DevOpenHelper extends OpenHelper {
            public DevOpenHelper(Context context, String name) {
                super(context, name);
            }
    
            public DevOpenHelper(Context context, String name, CursorFactory factory) {
                super(context, name, factory);
            }
    
            @Override
            public void onUpgrade(Database db, int oldVersion, int newVersion) {
                Log.i("greenDAO", "Upgrading schema from version " + oldVersion + " to " + newVersion + " by dropping all tables");
                dropAllTables(db, true);
                onCreate(db);
            }
        }
    
    }

package com.tongyonghangkong.greendao.gen;
    
    import java.util.Map;
    
    import org.greenrobot.greendao.AbstractDao;
    import org.greenrobot.greendao.AbstractDaoSession;
    import org.greenrobot.greendao.database.Database;
    import org.greenrobot.greendao.identityscope.IdentityScopeType;
    import org.greenrobot.greendao.internal.DaoConfig;
    
    import com.tongyonghangkong.bean.ZhenHang;
    import com.tongyonghangkong.bean.Wokers;
    
    import com.tongyonghangkong.greendao.gen.ZhenHangDao;
    import com.tongyonghangkong.greendao.gen.WokersDao;
    
    // THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT.
    
    /**
     * {@inheritDoc}
     * 
     * @see org.greenrobot.greendao.AbstractDaoSession
     */
    public class DaoSession extends AbstractDaoSession {
    
        private final DaoConfig zhenHangDaoConfig;
        private final DaoConfig wokersDaoConfig;
    
        private final ZhenHangDao zhenHangDao;
        private final WokersDao wokersDao;
    
        public DaoSession(Database db, IdentityScopeType type, Map<Class<? extends AbstractDao<?, ?>>, DaoConfig>
                daoConfigMap) {
            super(db);
    
            zhenHangDaoConfig = daoConfigMap.get(ZhenHangDao.class).clone();
            zhenHangDaoConfig.initIdentityScope(type);
    
            wokersDaoConfig = daoConfigMap.get(WokersDao.class).clone();
            wokersDaoConfig.initIdentityScope(type);
    
            zhenHangDao = new ZhenHangDao(zhenHangDaoConfig, this);
            wokersDao = new WokersDao(wokersDaoConfig, this);
    
            registerDao(ZhenHang.class, zhenHangDao);
            registerDao(Wokers.class, wokersDao);
        }
        
        public void clear() {
            zhenHangDaoConfig.getIdentityScope().clear();
            wokersDaoConfig.getIdentityScope().clear();
        }
    
        public ZhenHangDao getZhenHangDao() {
            return zhenHangDao;
        }
    
        public WokersDao getWokersDao() {
            return wokersDao;
        }
    
    }

复制到greenDao.gen的类之后，在APPlication中进行初始化greenDao： 调用setDatabase()方法

private void setDatabase() {
            mHelper = new DaoMaster.DevOpenHelper(this, "notes_db", null);
            db = mHelper.getWritableDatabase();
            mDaoMaster = new DaoMaster(db);
            mDaoSession = mDaoMaster.newSession();
        }
    
        public DaoSession getDaoSession() {
            return mDaoSession;
        }
    
        public SQLiteDatabase getDb() {
            return db;
        }

4 开始创建你的表

package com.tongyonghangkong.bean;
    
    import org.greenrobot.greendao.annotation.Entity;
    import org.greenrobot.greendao.annotation.Id;
    
    /**
     * Created by Administrator on 2019/3/12.
     */
    @Entity
    public class Wokers {
    
        @Id
        public Long id;
        public String name;
        public String age;
        public String sex;
        
    }

创建bean类，具体格式如上

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点击build的Make project 之后，自动生成的文件：

package com.tongyonghangkong.greendao.gen;
    
    import android.database.Cursor;
    import android.database.sqlite.SQLiteStatement;
    
    import org.greenrobot.greendao.AbstractDao;
    import org.greenrobot.greendao.Property;
    import org.greenrobot.greendao.internal.DaoConfig;
    import org.greenrobot.greendao.database.Database;
    import org.greenrobot.greendao.database.DatabaseStatement;
    
    import com.tongyonghangkong.bean.ZhenHang;
    
    // THIS CODE IS GENERATED BY greenDAO, DO NOT EDIT.
    /** 
     * DAO for table "ZHEN_HANG".
    */
    public class ZhenHangDao extends AbstractDao<ZhenHang, Long> {
    
        public static final String TABLENAME = "ZHEN_HANG";
    
        /**
         * Properties of entity ZhenHang.<br/>
         * Can be used for QueryBuilder and for referencing column names.
        */
        public static class Properties {
            public final static Property Id = new Property(0, Long.class, "id", true, "_id");
            public final static Property Name = new Property(1, String.class, "name", false, "NAME");
            public final static Property Age = new Property(2, int.class, "age", false, "AGE");
            public final static Property Sex = new Property(3, String.class, "sex", false, "SEX");
        };
    
    
        public ZhenHangDao(DaoConfig config) {
            super(config);
        }
        
        public ZhenHangDao(DaoConfig config, DaoSession daoSession) {
            super(config, daoSession);
        }
    
        /** Creates the underlying database table. */
        public static void createTable(Database db, boolean ifNotExists) {
            String constraint = ifNotExists? "IF NOT EXISTS ": "";
            db.execSQL("CREATE TABLE " + constraint + "\"ZHEN_HANG\" (" + //
                    "\"_id\" INTEGER PRIMARY KEY ," + // 0: id
                    "\"NAME\" TEXT NOT NULL ," + // 1: name
                    "\"AGE\" INTEGER NOT NULL ," + // 2: age
                    "\"SEX\" TEXT);"); // 3: sex
        }
    
        /** Drops the underlying database table. */
        public static void dropTable(Database db, boolean ifExists) {
            String sql = "DROP TABLE " + (ifExists ? "IF EXISTS " : "") + "\"ZHEN_HANG\"";
            db.execSQL(sql);
        }
    
        @Override
        protected final void bindValues(DatabaseStatement stmt, ZhenHang entity) {
            stmt.clearBindings();
     
            Long id = entity.getId();
            if (id != null) {
                stmt.bindLong(1, id);
            }
            stmt.bindString(2, entity.getName());
            stmt.bindLong(3, entity.getAge());
     
            String sex = entity.getSex();
            if (sex != null) {
                stmt.bindString(4, sex);
            }
        }
    
        @Override
        protected final void bindValues(SQLiteStatement stmt, ZhenHang entity) {
            stmt.clearBindings();
     
            Long id = entity.getId();
            if (id != null) {
                stmt.bindLong(1, id);
            }
            stmt.bindString(2, entity.getName());
            stmt.bindLong(3, entity.getAge());
     
            String sex = entity.getSex();
            if (sex != null) {
                stmt.bindString(4, sex);
            }
        }
    
        @Override
        public Long readKey(Cursor cursor, int offset) {
            return cursor.isNull(offset + 0) ? null : cursor.getLong(offset + 0);
        }    
    
        @Override
        public ZhenHang readEntity(Cursor cursor, int offset) {
            ZhenHang entity = new ZhenHang( //
                cursor.isNull(offset + 0) ? null : cursor.getLong(offset + 0), // id
                cursor.getString(offset + 1), // name
                cursor.getInt(offset + 2), // age
                cursor.isNull(offset + 3) ? null : cursor.getString(offset + 3) // sex
            );
            return entity;
        }
         
        @Override
        public void readEntity(Cursor cursor, ZhenHang entity, int offset) {
            entity.setId(cursor.isNull(offset + 0) ? null : cursor.getLong(offset + 0));
            entity.setName(cursor.getString(offset + 1));
            entity.setAge(cursor.getInt(offset + 2));
            entity.setSex(cursor.isNull(offset + 3) ? null : cursor.getString(offset + 3));
         }
        
        @Override
        protected final Long updateKeyAfterInsert(ZhenHang entity, long rowId) {
            entity.setId(rowId);
            return rowId;
        }
        
        @Override
        public Long getKey(ZhenHang entity) {
            if(entity != null) {
                return entity.getId();
            } else {
                return null;
            }
        }
    
        @Override
        protected boolean hasKey(ZhenHang entity) {
            return false;
        }
    
        @Override
        protected final boolean isEntityUpdateable() {
            return true;
        }
        
    }

插入数据举例：

DaoMaster daoMaster = new DaoMaster(getWritableDatabase());
            DaoSession daoSession = daoMaster.newSession();
            UserDao userDao = daoSession.getUserDao();
            userDao.insert(user);

删除数据举例：

DaoMaster daoMaster = new DaoMaster(getWritableDatabase());
            DaoSession daoSession = daoMaster.newSession();
            UserDao userDao = daoSession.getUserDao();
            userDao.delete(user);

更新数据举例：

DaoMaster daoMaster = new DaoMaster(getWritableDatabase());
            DaoSession daoSession = daoMaster.newSession();
            UserDao userDao = daoSession.getUserDao();
            userDao.update(user);

查找数据举例：

public List<User> queryUserList() {
            DaoMaster daoMaster = new DaoMaster(getReadableDatabase());
            DaoSession daoSession = daoMaster.newSession();
            UserDao userDao = daoSession.getUserDao();
            QueryBuilder<User> qb = userDao.queryBuilder();
            List<User> list = qb.list();
            return list;
        }

出错解决：

1 android.database.sqlite.SQLiteException: no such table: TASK\_SCAN (code 1): , while compiling: SELECT T."\_id",T."TASKID",T."TASKCARDID",T."TASKSTATUS" FROM "TASK\_SCAN" ……………………

使用greenDao过程中，新建了一个数据类Person并标注@Entity，然后框架自动生成了PersonDao，我使用这个Dao类来对Person表进行操作，然后安装到手机上后报了这个错。

报错信息说没有这个表，这让我非常郁闷，难道每次应用启动的时候框架不会自动检查所有数据表，把新建的数据类映射到数据库中吗？实践证明是不会的，只有应用第一次安装的时候才会在数据库中新建这些表，开发中删除当前的apk重新运行安装一个就可以。

解决方法也很明显了，删掉手机上原有APK再安装即可。

转载自：[http://blog.csdn.net/zhang\_\_\_yong/article/details/77948150][http_blog.csdn.net_zhang_yong_article_details_77948150]

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[http_greenrobot.org_greendao]: http://greenrobot.org/greendao/
[https_github.com_greenrobot_greenDAO]: https://github.com/greenrobot/greenDAO
[watermark_type_ZmFuZ3poZW5naGVpdGk_shadow_10_text_aHR0cHM6Ly9ibG9nLmNzZG4ubmV0L2NzZG5fbG92ZVFpbmdRaW5n_size_16_color_FFFFFF_t_70 1]: /images/20210901/52c614e9629a443885c669cfe5010b04.png
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[http_blog.csdn.net_zhang_yong_article_details_77948150]: http://blog.csdn.net/zhang___yong/article/details/77948150