【填坑往事】使用Rxjava2的distinct操作符处理自定义数据类型去重的问题

       最近碰到一个问题，自定义数据类型列表中出现了重复数据，需要去重。处理去重的办法很多，比如借助Set集合类，使用双重循环拿每一个元素和其他元素对比等。这里介绍一种简单而且比较优雅的方式：使用Rxjava2中的distinct操作符来实现。

       网上介绍这种方式的文章非常多，但基本上都是拿整数类型数据来演示，比如：

Observable.just(1, 1, 2, 2, 3, 4).distinct().subscribe(new Consumer<Integer>() {
            @Override
            public void accept(Integer integer) throws Exception {
                Log.d(TAG, "[distinct-accept]integer = " + integer);
            }
        });

但实际工作中碰到的数据类型却是自定义类型，看到上述代码后本人还是有时有点手足无措，没法直接拿到依葫芦画瓢。后来自己研究了一下，在上述代码基础上转了一个弯，解决了这个问题，下面记录一下。

使用的自定义类型为：

public class UserInfo {
    private String userId;
    private String userName;

    public UserInfo(String userId, String userName) {
        this.userId = userId;
        this.userName = userName;
    }

    public String getUserId() {
        return userId;
    }

    public void setUserId(String userId) {
        this.userId = userId;
    }

    public String getUserName() {
        return userName;
    }

    public void setUserName(String userName) {
        this.userName = userName;
    }

    @Override
    public boolean equals(Object o) {
        if (this == o) return true;
        if (o == null || getClass() != o.getClass()) return false;
        UserInfo userInfo = (UserInfo) o;
        return Objects.equals(userId, userInfo.userId);
    }

    @Override
    public int hashCode() {
        return Objects.hash(userId);
    }

    @Override
    public String toString() {
        return "UserInfo{" +
                "userId='" + userId + '\'' +
                ", userName='" + userName + '\'' +
                '}';
    }
}

测试代码为

private void testDistinct() {
    List<UserInfo> userInfoList = new ArrayList<>();
    userInfoList.add(new UserInfo("id-0", "name-0"));
    for (int i = 0; i < 10; i++) {
        userInfoList.add(new UserInfo("id-" + i, "name-" + i));
    }
    Log.d(TAG, "[testDistinct]去重前");
    for (UserInfo userInfo : userInfoList) {
        Log.d(TAG, "[testDistinct]userInfo = " + userInfo.toString());
    }
    Log.d(TAG, "[testDistinct]去重后");
    Observable.fromIterable(userInfoList).distinct().subscribe(new Consumer<UserInfo>() {
        @Override
        public void accept(UserInfo userInfo) throws Exception {
            Log.d(TAG, "[distinct-accept]userInfo = " + userInfo.toString());
        }
    });
}

日志

2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]去重前
 2 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-0', userName='name-0'}
 3 2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-0', userName='name-0'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-1', userName='name-1'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-2', userName='name-2'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-3', userName='name-3'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-4', userName='name-4'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-5', userName='name-5'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-6', userName='name-6'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-7', userName='name-7'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-8', userName='name-8'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]userInfo = UserInfo{userId='id-9', userName='name-9'}
2022-01-08 16:41:31.858 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [testDistinct]去重后
14 2022-01-08 16:41:31.870 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-0', userName='name-0'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-1', userName='name-1'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-2', userName='name-2'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-3', userName='name-3'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-4', userName='name-4'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-5', userName='name-5'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-6', userName='name-6'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-7', userName='name-7'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-8', userName='name-8'}
2022-01-08 16:41:31.871 12668-12668/com.beantechs.rxjavademo D/rxjava_demo: [distinct-accept]userInfo = UserInfo{userId='id-9', userName='name-9'}

日志中红色部分显示了去重效果。

       本示例中是把具有相同userId的对象视为同一个对象，所有在UserInfo类中重写了equals()方法和hashCode()方法，这是关键点。如果判断是否为同一对象的条件有变化，就需要相应地重写equals()方法和hashCode()方法。