GreenDao3.0的使用

        这个周末去看看GreenDao3.0数据库的使用，基本的增删改查倒是很easy，但是后面的数据库升级并保留先前的数据，看了一个下午的博客才弄出来，所以写出来记下笔记。

一、在project中的build.gradle中加入

classpath 'org.greenrobot:greendao-gradle-plugin:3.0.0'

如图：

二、然后是在module中添加依赖

greendao{
    schemaVersion 3
    targetGenDir 'src/main/java'
}

apply plugin: 'org.greenrobot.greendao'

compile'org.greenrobot:greendao:3.0.0'
compile'org.greenrobot:greendao-generator:3.0.0'

如图：

二、新建一个User的B 

三、下面简单封装了下

package DbUtils;

import android.app.Application;
import android.content.Context;

import Entity.DaoMaster;
import Entity.DaoSession;

/**
 * Created by Administrator on 2018/3/25.
 */

public class GreenDaoHelper extends Application {
    private GreenDaoHelper Instance;
    private static DaoMaster daoMaster;
    private static DaoSession daoSession;

    public GreenDaoHelper getInstance() {
        if (Instance == null) {
            Instance = this;
        }
        return Instance;
    }

    /**
     * 获取DaoMaster
     *
     * @param context
     * @return
     */
//    public static DaoMaster getDaoMaster(Context context) {
//        if (daoMaster == null) {
//            try{
//                DaoMaster.OpenHelper helper = new DaoMaster.DevOpenHelper(context,"test.db",null);
//                daoMaster = new DaoMaster(helper.getWritableDatabase()); //获取未加密的数据库
//            }catch (Exception e){
//                e.printStackTrace();
//            }
//        }
//        return daoMaster;
//    }

    public static DaoMaster getDaoMaster(Context context) {
        if (null == daoMaster) {
            synchronized (GreenDaoHelper.class) {
                if (null == daoMaster) {
                    MyOpenHelper helper = new MyOpenHelper(context,"test.db",null);
                    daoMaster = new DaoMaster(helper.getWritableDatabase());
                }
            }
        }
        return daoMaster;
    }

    /**
     * 获取DaoSession对象
     *
     * @param context
     * @return
     */
    public static DaoSession getDaoSession(Context context) {

        if (daoSession == null) {
            if (daoMaster == null) {
                getDaoMaster(context);
            }
            daoSession = daoMaster.newSession();
        }
        return daoSession;
    }

  下面是简单的增删改查的方法：

            

简单的增删改查实现：

1. 增

mUser = new User((long)2,"anye3");
mUserDao.insert(mUser);//添加一个

2. 删

mUserDao.deleteByKey(id);

3. 改

mUser = new User((long)2,"anye0803");
mUserDao.update(mUser);

4. 查

List<User> users = mUserDao.loadAll();
String userName = "";
for (int i = 0; i < users.size(); i++) {
    userName += users.get(i).getName()+",";
}
mContext.setText("查询全部数据==>"+userName);

    下面贴下我的Activity

            

public class HomeActivity extends Activity {
    @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        setContentView(R.layout.activity_main);

//        GreenDaoHelper greenDaoHelper = new GreenDaoHelper().getInstance();
        UserDao userDao = GreenDaoHelper.getDaoSession(this).getUserDao();

        User user = new User(null, "ZZH","张三","白色",23);
        userDao.insert(user);


        List<User> users = userDao.loadAll();
        String userName = "";
        String color = "";
        Integer integer =0;
        for (int i = 0; i < users.size(); i++) {
            userName += users.get(i).getUsername()+",";
            color += users.get(i).getColor()+",";
            integer += users.get(i).getAge();
        }
        ((TextView)findViewById(R.id.text)).setText("查询全部数据==>"+userName+""+color+""+integer);
    }

}

现在就能简单的使用增删改查了。

四、数据库保存之前的数据并升级

首先要 MigrationHelper这个类，也是别人大神写好的，我直接拿来用的，大家用兴趣可以仔细看看源码，我自己也在学习中。

package DbUtils;

import android.database.Cursor;
import android.text.TextUtils;
import android.util.Log;

import org.greenrobot.greendao.AbstractDao;
import org.greenrobot.greendao.database.Database;
import org.greenrobot.greendao.internal.DaoConfig;

import java.util.ArrayList;
import java.util.Arrays;
import java.util.List;

import Entity.DaoMaster;

/**
 * Created by Administrator on 2018/3/25.
 */

public class MigrationHelper {

    private static final String CONVERSION_CLASS_NOT_FOUND_EXCEPTION = "MIGRATION HELPER - CLASS DOESN'T MATCH WITH THE CURRENT PARAMETERS";
    private static MigrationHelper instance;

    public static MigrationHelper getInstance() {
        if (instance == null) {
            instance = new MigrationHelper();
        }
        return instance;
    }

    public void migrate(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {

        generateTempTables(db, daoClasses);
        DaoMaster.dropAllTables(db, true);
        DaoMaster.createAllTables(db, false);
        restoreData(db, daoClasses);
    }

    /**
     * 生成临时列表
     *
     * @param db
     * @param daoClasses
     */
    private void generateTempTables(Database db, Class<? extends AbstractDao<?, ?>>... daoClasses) {
        for (int i = 0; i < daoClasses.length; i++) {
            DaoConfig daoConfig = new DaoConfig(db, daoClasses[i]);

            String divider = "";
            String tableName = daoConfig.tablename;
            String tempTableName = daoConfig.tablename.concat("_TEMP");
            ArrayList<String> properties = new ArrayList<>();

            StringBuilder createTableStringBuilder = new StringBuilder();

            createTableStringBuilder.append("CREATE TABLE ").append(tempTableName).append(" (");

            for (int j = 0; j < daoConfig.properties.length; j++) {
                String columnName = daoConfig.properties[j].columnName;

                if (getColumns(db, tableName).contains(columnName)) {
                    properties.add(columnName);

                    String type = null;

                    try {
                        type = getTypeByClass(daoConfig.properties[j].type);
                    } catch (Exception exception) {
                        exception.printStackTrace();
                    }

                    createTableStringBuilder.append(divider).append(columnName).append(" ").append(type);

                    if (daoConfig.properties[j].primaryKey) {
                        createTableStringBuilder.append(" PRIMARY KEY");
                    }

                    divider = ",";
                }
            }
            createTableStringBuilder.append(");");

            db.execSQL(createTableStringBuilder.toString());

            StringBuilder insertTableStringBuilder = new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tempTableName).append(" (");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(") SELECT ");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(" FROM ").append(tableName).append(";");

            db.execSQL(insertTableStringBuilder.toString());

        }
    }

    /**
     * 存储新的数据库表 以及数据
     *
     * @param db
     * @param daoClasses
     */
    private 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");
            ArrayList<String> properties = new ArrayList();

            for (int j = 0; j < daoConfig.properties.length; j++) {
                String columnName = daoConfig.properties[j].columnName;

                if (getColumns(db, tempTableName).contains(columnName)) {
                    properties.add(columnName);
                }
            }

            StringBuilder insertTableStringBuilder = new StringBuilder();

            insertTableStringBuilder.append("INSERT INTO ").append(tableName).append(" (");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(") SELECT ");
            insertTableStringBuilder.append(TextUtils.join(",", properties));
            insertTableStringBuilder.append(" FROM ").append(tempTableName).append(";");

            StringBuilder dropTableStringBuilder = new StringBuilder();
            dropTableStringBuilder.append("DROP TABLE ").append(tempTableName);
            db.execSQL(insertTableStringBuilder.toString());
            db.execSQL(dropTableStringBuilder.toString());
        }
    }

    private String getTypeByClass(Class<?> type) throws Exception {
        if (type.equals(String.class)) {
            return "TEXT";
        }
        if (type.equals(Long.class) || type.equals(Integer.class) || type.equals(long.class)) {
            return "INTEGER";
        }
        if (type.equals(Boolean.class)) {
            return "BOOLEAN";
        }

        Exception exception = new Exception(CONVERSION_CLASS_NOT_FOUND_EXCEPTION.concat(" - Class: ").concat(type.toString()));
        exception.printStackTrace();
        throw exception;
    }

    private List<String> getColumns(Database db, String tableName) {
        List<String> columns = new ArrayList<>();
        Cursor cursor = null;
        try {
            cursor = db.rawQuery("SELECT * FROM " + tableName + " limit 1", null);
            if (cursor != null) {
                columns = new ArrayList<>(Arrays.asList(cursor.getColumnNames()));
            }
        } catch (Exception e) {
            Log.v(tableName, e.getMessage(), e);
            e.printStackTrace();
        } finally {
            if (cursor != null)
                cursor.close();
        }
        return columns;
    }
}

你要知道更新是在DaoMaster中OpenHelper的onUpgrade方法中进行的，所以我们要重写这个方法

package DbUtils;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;

import org.greenrobot.greendao.database.Database;

import Entity.DaoMaster;
import Entity.UserDao;

/**
 * Created by Administrator on 2018/3/25.
 */

public class MyOpenHelper extends DaoMaster.OpenHelper {

    public MyOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory) {
        super(context, name, factory);
    }

    /**
     * 数据库升级
     * @param db
     * @param oldVersion
     * @param newVersion
     */
    @Override
    public void onUpgrade(Database db, int oldVersion, int newVersion) {
        //操作数据库的更新 有几个表升级都可以传入到下面
        MigrationHelper.getInstance().migrate(db, UserDao.class);
    }

}

最后在module中build.gradle中修改 schemaVersion为2，因为版本高了才会触发onUpgrade方法

greendao{
    schemaVersion 2
    targetGenDir 'src/main/java'
}