原文地址:
https://blog.csdn.net/byhook/article/details/83343016\
变换操作符
- map操作符
- flatMap操作符
- flatMapIterable操作符
- concatMap操作符
- switchMap操作符
- cast操作符
- scan操作符
- buffer操作符
- toList操作符
- groupBy操作符
- toMap操作符
map
map操作符作为基本的转换操作符，可以把每一个元素转换成新的元素发射
Observable.just(0, 1, 2, 3, 4, 5)
.map(new Function() {
@Override
public String apply(Integer integer) throws Exception {
return "apply " + integer;
}
})
.subscribe(new CommonComsumer<>());
输出:
accept apply 0
accept apply 1
accept apply 2
accept apply 3
accept apply 4
accept apply 5
Process finished with exit code 0
flatMap
flatMap操作符将每个元素转换成被观察者,每个被观察者发送的元素会合并成新的被观察者,顺序输出
Student类
public class Student {
public int age;
public String name;
public List courses;
public int getAge() {
return age;
}
public void setAge(int age) {
this.age = age;
}
public String getName() {
return name;
}
public void setName(String name) {
this.name = name;
}
public List getCourses() {
return courses;
}
public void setCourses(List courses) {
this.courses = courses;
}
public static List create() {
List students = new ArrayList<>();
Student student;
for (int i = 0; i < 5; i++) {
student = new Student();
student.setAge(i);
student.setName("name " + i);
student.setCourses(Arrays.asList(1, 2, 3));
students.add(student);
}
return students;
}
}
List students = Student.create();
Observable.fromIterable(students)
.flatMap(value -> {
return Observable.fromIterable(value.courses);
}).subscribeWith(new CommonObserver<>());
输出:
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onComplete
Process finished with exit code 0
flatMapIterable
flatMapIterable操作符与flatMap类似,但它可以将每个元素转化成iterable
List students = Student.create();
Observable.fromIterable(students)
.flatMapIterable(new Function>() {
@Override
public Iterable apply(Student student) throws Exception {
return student.courses;
}
}).subscribeWith(new CommonObserver<>());
输出:
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onComplete
Process finished with exit code 0
concatMap
concatMap操作符和flatMap类似,flatMap内部通过merge合并元素,顺序可能会错乱,但是concatMap内部安装concat合并元素,按照顺序发射
List students = Student.create();
Observable.fromIterable(students)
.concatMap(value -> {
return Observable.fromIterable(value.courses);
}).subscribeWith(new CommonObserver<>());
输出:
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onNext 1
onNext 2
onNext 3
onComplete
Process finished with exit code 0
switchMap
switchMap操作符每次转换出来新的数据都会取代前一个被观察者
Observable.just(0, 1, 2)
.switchMap(value -> {
return Observable.timer(1, TimeUnit.SECONDS).map(longValue -> value);
}).subscribeWith(new CommonObserver<>());
输出:
onNext 2
onComplete
Process finished with exit code 0
cast
cast操作符主要用来强制转换每一个元素的类型
Observable.just(1, 2, 3, 4, 5)
//把每个元素都转换成Number类型,然后再发射
.cast(Number.class).subscribeWith(new CommonObserver<>());
输出:
onNext 1
onNext 2
onNext 3
onNext 4
onNext 5
onComplete
Process finished with exit code 0
scan
scan操作符扫描每一个元素,忽略第一个元素,从第二个元素开始进行变换后返回
Observable.just(1, 2, 3, 4, 5)
.scan(new BiFunction() {
@Override
public Integer apply(Integer value1, Integer value2) throws Exception {
return value2 + 1;
}
}).subscribeWith(new CommonObserver<>());
输出:
onNext 1
onNext 3
onNext 4
onNext 5
onNext 6
onComplete
Process finished with exit code 0
buffer
buffer操作符主要用来把多个元素打包成一个元素一次过发送数据
Observable.just(1, 2, 3, 4, 5, 6, 7, 8)
.buffer(3).subscribeWith(new CommonObserver<>());
输出:
onNext [1, 2, 3]
onNext [4, 5, 6]
onNext [7, 8]
onComplete
Process finished with exit code 0
toList
toList操作符主要用来把所有元素转换成一个List一次过发送出去
Observable.just(1, 2, 3, 4, 5, 6, 7, 8)
.toList().subscribe(new CommonComsumer<>());
输出:
accept [1, 2, 3, 4, 5, 6, 7, 8]
Process finished with exit code 0
groupBy
groupBy操作符会将接收到的数据分组key
Observable.just(1, 2, 3, 4, 5, 6, 7, 8)
.groupBy(new Function() {
@Override
public String apply(Integer integer) throws Exception {
return integer >= 5 ? "A组" : "B组";
}
}).subscribe(new Consumer>() {
@Override
public void accept(GroupedObservable observable) throws Exception {
observable.subscribe(new Consumer() {
@Override
public void accept(Integer integer) throws Exception {
String key = observable.getKey();
System.out.println(key + ":" + String.valueOf(integer));
}
});
}
});
输出:
B组:1
B组:2
B组:3
B组:4
A组:5
A组:6
A组:7
A组:8
Process finished with exit code 0
toMap
toMap操作符主要用来将元素转换成key,value对应的map
Observable.just(1, 2, 3, 4, 5, 6, 7, 8)
.toMap(new Function() {
@Override
public String apply(Integer integer) throws Exception {
return integer >= 5 ? "A组" : "B组";
}
}).subscribe(new CommonComsumer<>());
输出:
accept {B组=4, A组=8}
Process finished with exit code 0
复习文档
https://github.com/byhook/rxjava2-study
参考:
https://maxwell-nc.github.io/android/rxjava2-6.html