Android-->Realm(数据库ORM)使用体验,lambda表达式

Posted 2020-10-29 llguanli

Realm，为移动设备而生。替代 SQLite 和 Core Data。

非常庆幸,官方帮助文档有中文: https://realm.io/cn/docs/java/latest/
尽管眼下最新的版本号0.88.3,连1.0的版本号都没有公布…可是全然不影响她的强大;

API文档: https://realm.io/docs/java/latest/api/

因为官方的帮助文档,有中文的…大家看起来非常easy懂,我这里仅仅依据个人使用经验,写写体验.

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1:Realm的引用

Project级别的build.gradle文件:

buildscript {
    repositories {
        jcenter()
    }
    dependencies {
        classpath ‘com.android.tools.build:gradle:2.1.0-beta3‘
        classpath ‘me.tatarka:gradle-retrolambda:3.3.0-beta4‘ //lambda表达式配置步骤1
        classpath "io.realm:realm-gradle-plugin:0.88.3"//注意此行
    }
}

allprojects {
    repositories {
        jcenter()
    }
}

Module级别的build.gradle

apply plugin: ‘com.android.application‘
apply plugin: ‘me.tatarka.retrolambda‘ //lambda表达式配置步骤2
apply plugin: ‘realm-android‘ //注意此行

android {
    ...
    //lambda表达式配置步骤3,结束.
    compileOptions {
        encoding "UTF-8"
        targetCompatibility JavaVersion.VERSION_1_8
        sourceCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {
    ...
}

(彩蛋:上述中,包括了lambda表达式的配置步骤…你懂得)

2:增删改查的操作

//封装的操作类
public class RRealm {
  /**
   * 必须调用的方法
   */
  public static void init(Context context, String name, boolean clean) {
      RealmConfiguration configuration = new RealmConfiguration.Builder(context).name(name).build();
      if (clean) {
          Realm.deleteRealm(configuration);
      }
      Realm.setDefaultConfiguration(configuration);
  }

  public static Realm realm() {
      return Realm.getDefaultInstance();
  }

  /**
   * 通常能够直接此方法
   */
  public static void operate(OnOperate operate) {
      if (operate != null) {
          Realm realm = realm();
          realm.beginTransaction();
          operate.on(realm);
          realm.commitTransaction();
          realm.close();
      }
  }

  public interface OnOperate {
      void on(Realm realm);
  }

}

private void add() {
    RRealm.operate(realm -> {
        for (int i = 0; i < Num; i++) {
            TestRealmObject realmObject = realm.createObject(TestRealmObject.class);
            realmObject.setAge(i);
            realmObject.setName("name" + i);
            realmObject.setTest("test" + i);
            realmObject.setTime(System.currentTimeMillis());
        }
    });
}

private void delete() {
    RRealm.operate(realm -> {
        RealmResults<TestRealmObject> all = realm.where(TestRealmObject.class).findAll();
        all.clear();
    });
}

private void update() {
    RRealm.operate(realm -> {
        RealmResults<TestRealmObject> all = realm.where(TestRealmObject.class).findAll();
        for (int i = 0; i < all.size(); i++) {
            TestRealmObject object = all.get(i);
            object.setName(object.getName() + " new");
            object.setTest(object.getTest() + " new");
        }
    });
}

private void query() {
    RRealm.operate(realm -> {
        RealmQuery<TestRealmObject> where = realm.where(TestRealmObject.class);
        RealmResults<TestRealmObject> all = where.findAll();
        for (TestRealmObject object : all) {
            e(object.toString());
        }
    });
}

3:性能评估

//測试类
public class TestRealmObject extends RealmObject {
    public String name;
    public int age;
    public long time;
    public String test;
}
//插入1000条数据: 149 毫秒 148  158  118
//查询1000条数据: 146 毫秒 183  178  192
//删除1000条数据: 39  毫秒  44   37   38
//更新1000条数据: 212 毫秒 195  185  216
//数据仅供參考

再次提醒:官方有中文文档,大家能够具体阅读,会比較好;

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