Android GreenDao

离线开发

开发工具： androidStudio ,SQLite3

使用开源库：GreenDao 3.2.2

离线已实现：

1. 增、删、改、查

2. 新增表，字段，更改字段，升级数据迁移

3. 从服务器下载数据，并更新到本地数据表，避免重复添加

4. 代码封装

集成：

1. 项目根目录添加环境

buildscript {...dependencies {classpath 'com.android.tools.build:gradle:3.6.0'classpath 'org.greenrobot:greendao-gradle-plugin:3.2.2' // 添加 GreenDao 插件}
}
allprojects {repositories {google()jcenter()maven { url 'https://jitpack.io' } // 添加}
}

2. app 下添加依赖

// 与 application 同级
apply plugin: 'com.android.application'
apply plugin: 'org.greenrobot.greendao'// android 节点中，rootProject.ext.publish.versionCode 文尾介绍
greendao {// 数据库升级视为 App 重大升级，跟随 versionCode ，方便记忆schemaVersion rootProject.ext.publish.versionCode
}// dependencies 节点中
implementation 'org.greenrobot:greendao:3.2.2' // 添加

3. 对象，也就是表

@Entity(nameInDb = "Users")
public class UserBean {@Id(autoincrement = true)@Index(unique = true)//设置唯一性@Property(nameInDb = "F_id")private Long F_id;@Property(nameInDb = "F_byyx")private String F_byyx;@Property(nameInDb = "F_csrq")private String F_csrq;...
}

4. 普通的增删改查

UserBeanDao userBeanDao = DaoManager.getInstance().getDaoSession().getUserBeanDao();// 增
userBeanDao.insert(new UserBean(100L, "王大锤", "女"));// 删
userBeanDao.deleteByKey(100L);// 改
UserBean bean = mUserBeanDao.load(32L);
bean.setF_csrq("改改");
userBeanDao.update(bean);// 查
StringBuilder sb = new StringBuilder();
List<UserBean> userBeans = mUserBeanDao.loadAll();
for (UserBean userBean : userBeans) {sb.append("id:").append(userBean.getId()).append("f_id:").append(userBean.getF_id()).append("F_byyx:").append(userBean.getF_byyx()).append("F_csrq:").append(userBean.getF_csrq()).append("\n");
}
Log.i(TAG, "showDataList: "+sb.toString();

5. 新增表，字段，更改字段，升级时数据迁移，最后全部代码介绍

// 这里升级最好是将所有的表都写上，工具类会自动进行数据迁移MigrationHelper.migrate(db,StuffBeanDao.class,DepartmentBeanDao.class);

6. 从服务器下载数据，并更新到本地数据表，业务上会一次下载多张表，所以我统一放到了一个子线程中处理（真正实现过程使用的 IntentService ，其内部就是子线程，用完后，会自动销毁）

// 模拟网络数据
List<UserBean> list = new ArrayList<>();
list.add(new UserBean( 111L, "王大宝", "男"));
list.add(new UserBean( 112L, "王大宝", "男"));
list.add(new UserBean( 113L, "王大宝", "男"));
list.add(new UserBean( 114L, "王大宝", "男"));
list.add(new UserBean( 115L, "王大宝", "男"));
list.add(new UserBean( 116L, "王大宝", "男"));
list.add(new UserBean( 117L, "王大宝", "男"));// 更新或插入操作
for (int i = 0; i < list.size(); i++) {UserBean bean = list.get(i);// dao.hasKey(bean) 这句话只是说这个对象中是否存在主键，因为我设置了主键所以肯定存在// mUserBeanDao.load(bean.getF_id()) != null ，查询看看是否存在，存在则更新，不存在则插入if (mUserBeanDao.load(bean.getF_id()) != null) {mUserBeanDao.update(bean);} else {mUserBeanDao.insert(bean);}}

全部源码

// 常量
public interface DbConstants {String DB_NAME = "test.db";// 数据库名称}// 应用启动类
public class GreenDaoApplication extends Application {@Overridepublic void onCreate() {super.onCreate();initGreenDao();}/*** 初始化 GreenDao 数据库*/private void initGreenDao() {DaoManager.getInstance().init(this);DaoManager.getInstance().getDaoMaster();}
}// 数据迁移类
public final class MigrationHelper {private static final String TAG = "MigrationHelper";private static final String SQLITE_MASTER = "sqlite_master";private static final String SQLITE_TEMP_MASTER = "sqlite_temp_master";public static void migrate(SQLiteDatabase db, Class<? extends AbstractDao<?, ?>>... daoClasses) {LogUtil.d(TAG,"【The Old Database Version】" + db.getVersion());Database database = new StandardDatabase(db);migrate(database, daoClasses);}public static void migrate(Database database, Class<? extends AbstractDao<?, ?>>... daoClasses) {LogUtil.d(TAG,"【Generate temp table】start");generateTempTables(database, daoClasses);LogUtil.d(TAG,"【Generate temp table】complete");LogUtil.d(TAG,"【Drop all table and recreate all table】");for (int i = 0; i < daoClasses.length; i++) {DaoConfig daoConfig = new DaoConfig(database, daoClasses[i]);dropTable(database, true, daoConfig);createTable(database, false, daoConfig);}LogUtil.d(TAG,"【Restore data】start");restoreData(database, daoClasses);LogUtil.d(TAG,"【Restore data】complete");}private static void dropTable(Database database, boolean ifExists, DaoConfig daoConfig) {String sql = String.format("DROP TABLE %s\"%s\"", ifExists ? "IF EXISTS " : "", daoConfig.tablename);database.execSQL(sql);}private static void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {for (int i = 0; i < daoClasses.length; i++) {String tempTableName = null;DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);String tableName = daoConfig.tablename;if (!isTableExists(db, false, tableName)) {LogUtil.d(TAG,"【New Table】" + tableName);continue;}try {tempTableName = daoConfig.tablename.concat("_TEMP");StringBuilder dropTableStringBuilder = new StringBuilder();dropTableStringBuilder.append("DROP TABLE IF EXISTS ").append(tempTableName).append(";");LogUtil.d(TAG,"【Generate temp table】 dropTableStringBuilder:" + dropTableStringBuilder);db.execSQL(dropTableStringBuilder.toString());StringBuilder insertTableStringBuilder = new StringBuilder();insertTableStringBuilder.append("CREATE TEMPORARY TABLE ").append(tempTableName);insertTableStringBuilder.append(" AS SELECT * FROM ").append(tableName).append(";");LogUtil.d(TAG,"【Generate temp table】 insertTableStringBuilder:" + insertTableStringBuilder);db.execSQL(insertTableStringBuilder.toString());LogUtil.d(TAG,"【Table】" + tableName +"\n ---Columns-->" + getColumnsStr(daoConfig));LogUtil.d(TAG,"【Generate temp table】" + tempTableName);} catch (SQLException e) {Log.e(TAG, "【Failed to generate temp table】" + tempTableName, e);}}}private static boolean isTableExists(Database db, boolean isTemp, String tableName) {if (db == null || TextUtils.isEmpty(tableName)) {return false;}String dbName = isTemp ? SQLITE_TEMP_MASTER : SQLITE_MASTER;String sql = "SELECT COUNT(*) FROM " + dbName + " WHERE type = ? AND name = ?";Cursor cursor=null;int count = 0;try {cursor = db.rawQuery(sql, new String[]{"table", tableName});if (cursor == null || !cursor.moveToFirst()) {return false;}count = cursor.getInt(0);} catch (Exception e) {e.printStackTrace();} finally {if (cursor != null)cursor.close();}return count > 0;}private static String getColumnsStr(DaoConfig daoConfig) {if (daoConfig == null) {return "no columns";}StringBuilder builder = new StringBuilder();for (int i = 0; i < daoConfig.allColumns.length; i++) {builder.append(daoConfig.allColumns[i]);builder.append(",");}if (builder.length() > 0) {builder.deleteCharAt(builder.length() - 1);}return builder.toString();}private static void restoreData(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {for (int i = 0; i < daoClasses.length; i++) {DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);String tableName = daoConfig.tablename;String tempTableName = daoConfig.tablename.concat("_TEMP");if (!isTableExists(db, true, tempTableName)) {continue;}try {// get all columns from tempTable, take careful to use the columns listList<String> columns = getColumns(db, tempTableName);ArrayList<String> properties = new ArrayList<>(columns.size());for (int j = 0; j < daoConfig.properties.length; j++) {String columnName = daoConfig.properties[j].columnName;if (columns.contains(columnName)) {properties.add(columnName);}}if (properties.size() > 0) {final String columnSQL = TextUtils.join(",", properties);StringBuilder insertTableStringBuilder = new StringBuilder();insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");insertTableStringBuilder.append(columnSQL);insertTableStringBuilder.append(") SELECT ");insertTableStringBuilder.append(columnSQL);insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");LogUtil.d(TAG,"【Restore data】 db sql: " + insertTableStringBuilder);db.execSQL(insertTableStringBuilder.toString());LogUtil.d(TAG,"【Restore data】 to " + tableName);}StringBuilder dropTableStringBuilder = new StringBuilder();dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);db.execSQL(dropTableStringBuilder.toString());LogUtil.d(TAG,"【Drop temp table】" + tempTableName);} catch (SQLException e) {Log.e(TAG, "【Failed to restore data from temp table 】" + tempTableName, e);}}}private static List<String> getColumns(Database db, String tableName) {List<String> columns = null;Cursor cursor = null;try {cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 0", null);if (null != cursor && cursor.getColumnCount() > 0) {columns = Arrays.asList(cursor.getColumnNames());}} catch (Exception e) {e.printStackTrace();} finally {if (cursor != null)cursor.close();if (null == columns)columns = new ArrayList<>();}return columns;}public static void createTable(Database db, boolean ifNotExists, DaoConfig daoConfig) {String tableName = daoConfig.tablename;StringBuilder builder = new StringBuilder();builder.append("CREATE TABLE ");builder.append(ifNotExists ? "IF NOT EXISTS ": "");builder.append(tableName);builder.append(getColumnsSql(daoConfig));LogUtil.d(TAG,"【createTable】 sql:" + builder.toString());db.execSQL(builder.toString()); // 6: Description}private static String getColumnsSql(DaoConfig daoConfig) {if (daoConfig == null) {return "";}StringBuilder builder = new StringBuilder(" (");for (int i = 0; i < daoConfig.properties.length; i++) {builder.append(String.format("\"%s\" %s,", daoConfig.properties[i].columnName,getPropertyType(daoConfig.properties[i].type)));}if (daoConfig.properties.length > 0 && builder.length() > 0) {builder.deleteCharAt(builder.length() - 1);}builder.append("); ");return builder.toString();}/*** 根据字段类型返回对应的数据库字段语句* @param type* @return*/private static String getPropertyType(Class<?> type) {if (type.equals(byte[].class)) {return "BLOB";} else if (type.equals(String.class)) {return "TEXT DEFAULT ''";} else if (type.equals(boolean.class) || type.equals(Boolean.class)|| type.equals(int.class) || type.equals(Integer.class)|| type.equals(long.class) || type.equals(Long.class)|| type.equals(Date.class) || type.equals(Byte.class)) {return "INTEGER DEFAULT (0)";} else if (type.equals(float.class) || type.equals(Float.class)|| type.equals(double.class) || type.equals(Double.class)){return "REAL DEFAULT (0)";}return "TEXT DEFAULT ''";}}// 数据库管理类，封装
public class DaoManager {private Context mContext;//创建数据库的名字private static final String DB_NAME = DbConstants.DB_NAME;//多线程中要被共享的使用volatile关键字修饰  GreenDao管理类private volatile static DaoManager mInstance;//它里边实际上是保存数据库的对象private static DaoMaster mDaoMaster;//创建数据库的工具private static DbOpenHelper mHelper;//管理gen里生成的所有的Dao对象里边带有基本的增删改查的方法private static DaoSession mDaoSession;private DaoManager() {}/*** 单例模式获得操作数据库对象** @return*/public static DaoManager getInstance() {if (mInstance == null) {synchronized (DaoManager.class) {if (mInstance == null) {mInstance = new DaoManager();}}}return mInstance;}/*** 初始化上下文创建数据库的时候使用*/public void init(Context context) {this.mContext = context;}/*** 判断是否有存在数据库，如果没有则创建** @return*/public DaoMaster getDaoMaster() {if (mDaoMaster == null) {mHelper = new DbOpenHelper(mContext,DB_NAME);mDaoMaster = new DaoMaster(mHelper.getWritableDatabase());}return mDaoMaster;}/*** 完成对数据库的添加、删除、修改、查询操作，** @return*/public DaoSession getDaoSession() {if (mDaoSession == null) {if (mDaoMaster == null) {mDaoMaster = getDaoMaster();}mDaoSession = mDaoMaster.newSession(IdentityScopeType.None);}return mDaoSession;}/*** 关闭所有的操作，数据库开启后，使用完毕要关闭*/public void closeConnection() {closeHelper();closeDaoSession();}public void closeHelper() {if (mHelper != null) {mHelper.close();mHelper = null;}}public void closeDaoSession() {if (mDaoSession != null) {mDaoSession.clear();mDaoSession = null;}}
}// 升级时需要的类public class DbOpenHelper extends DaoMaster.OpenHelper {public DbOpenHelper(Context context, String name) {super(context, name);}@Overridepublic void onCreate(Database db) {super.onCreate(db);startMigrate(db);}@Overridepublic void onUpgrade(Database db, int oldVersion, int newVersion) {super.onUpgrade(db, oldVersion, newVersion);startMigrate(db);}private void startMigrate(Database db) {// 这里升级最好是将所有的表都写上，关键是数据库一定要更新,版本 和 app 同步，MigrationHelper.migrate(db,StuffBeanDao.class,DepartmentBeanDao.class);}}

文章结尾：

解释：schemaVersion rootProject.ext.publish.versionCode ，就是全局配置，如果依赖库多了方便管理

步骤1：在项目根目录新建 config.gradle 文件

ext {android = [compileSdkVersion: 29,buildToolsVersion: "28.0.0",minSdkVersion    : 19,targetSdkVersion : 28,supportLibVersion: "28.0.0"]publish = [applicationId: "com.test.test",versionCode  : 1,versionName  : "1.0"]
}

步骤2：在项目根目录 build.gradle 文件顶部引入

apply from: "config.gradle"

步骤3：在 App build.gradle 文件中使用

greendao {// 跟随 versionCode todo 数据库升级视为 App 重大升级，直接升级 VersionCode & VersionNameschemaVersion rootProject.ext.publish.versionCode
}

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