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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"

apply plugin: ‘realm-android‘

realm的创建

1、获取默认realm

 Realm myRealm = Realm.getDefaultInstance();

if (defaultConfiguration == null) {
            throw new NullPointerException("No default RealmConfiguration was found. Call setDefaultConfiguration() first");
        }

指定明确的RealmConfiguration可以获取指定Realm实例

   Realm.getInstance(new RealmConfiguration.Builder(MainActivity.this).build());

官方代码示例

// Define you model class by extending RealmObject
public 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 objects
Dog 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 thread
Realm realm = Realm.getDefaultInstance();

// Query Realm for all dogs younger than 2 years old
final 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 transaction
realm.beginTransaction();
final Dog managedDog = realm.copyToRealm(dog); // Persist unmanaged objects
Person person = realm.createObject(Person.class); // Create managed objects directly
person.getDogs().add(managedDog);
realm.commitTransaction();

// Listeners will be notified when data changes
puppies.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 thread
realm.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
    }
});

https://realm.io/docs/java/latest/#models

后续做一下文档翻译，源码解析。

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Realm使用简单介绍

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原文地址：http://blog.csdn.net/robertcpp/article/details/52097087