简介
Realm是一个轻量级的数据库，在Android开发中，它可以替代 SQLite 和 ORM 框架。相比SQLite，Realm更快并且具有很多现代数据库的特性，比如支持JSON，流式api，数据变更通知，以及加密支持。
官网主页:realm官网
GutHub地址：realm的GitHub地址
工程配置
1、在工程根目录的build.gradle中添加dependencies
classpath "io.realm:realm-gradle-plugin:1.1.0"2、在app的build.gradle中添加plugin
apply plugin: 'realm-android'注意：不需要再配置compile dependencies
realm的创建
1、获取默认realm
Realm myRealm = Realm.getDefaultInstance();
需要注意，在调用这个方法之前一定要先setDefaultConfiguration，否则会抛异常
if (defaultConfiguration == null) { throw new NullPointerException("No default RealmConfiguration was found. Call setDefaultConfiguration() first"); }RealmConfiguration必须通过Builder构建，
RealmConfiguration的构造方法是私有的。
指定明确的RealmConfiguration可以获取指定Realm实例
Realm.getInstance(new RealmConfiguration.Builder(MainActivity.this).build());
2、创建RealmObject
一个类继承了RealmObject，那么它就可以用来存储Realm
官方代码示例
// Define you model class by extending RealmObjectpublic class Dog extends RealmObject { private String name; private int age; // ... Generated getters and setters ...}public class Person extends RealmObject { @PrimaryKey private long id; private String name; private RealmList<Dog> dogs; // Declare one-to-many relationships // ... Generated getters and setters ...}// Use them like regular java objectsDog dog = new Dog();dog.setName("Rex");dog.setAge(1);// Create a RealmConfiguration that saves the Realm file in the app's "files" directory.RealmConfiguration realmConfig = new RealmConfiguration.Builder(context).build();Realm.setDefaultConfiguration(realmConfig);// Get a Realm instance for this threadRealm realm = Realm.getDefaultInstance();// Query Realm for all dogs younger than 2 years oldfinal RealmResults<Dog> puppies = realm.where(Dog.class).lessThan("age", 2).findAll();puppies.size(); // => 0 because no dogs have been added to the Realm yet// Persist your data in a transactionrealm.beginTransaction();final Dog managedDog = realm.copyToRealm(dog); // Persist unmanaged objectsPerson person = realm.createObject(Person.class); // Create managed objects directlyperson.getDogs().add(managedDog);realm.commitTransaction();// Listeners will be notified when data changespuppies.addChangeListener(new RealmChangeListener<RealmResults<Dog>>() { @Override public void onChange(RealmResults<Dog> results) { // Query results are updated in real time puppies.size(); // => 1 }});// Asynchronously update objects on a background threadrealm.executeTransactionAsync(new Realm.Transaction() { @Override public void execute(Realm bgRealm) { Dog dog = bgRealm.where(Dog.class).equalTo("age", 1).findFirst(); dog.setAge(3); }}, new Realm.Transaction.OnSuccess() { @Override public void onSuccess() { // Original queries and Realm objects are automatically updated. puppies.size(); // => 0 because there are no more puppies younger than 2 years old managedDog.getAge(); // => 3 the dogs age is updated }});
官方文档地址
https://realm.io/docs/java/latest/#models
后续做一下文档翻译，源码解析。
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