检索嵌套的对象我想以检索数据作为下一张照片如何火力数据
这里就是Ø从火力地堡文档得到
mCoursesChild.child("Courses").addListenerForSingleValueEvent(new ValueEventListener() {
@Override
public void onDataChange(DataSnapshot dataSnapshot) {
for (DataSnapshot data : dataSnapshot.getChildren()) {
Course temp = data.getValue(Course.class);
courses.add(temp));
}
}
@Override
public void onCancelled(DatabaseError databaseError) {
}
});
和“课程“被定义为ArrayList
ArrayList<Course> courses = new ArrayList<>();
这里是Cours E级
public class Course {
private String mCourseName;
List<Subject> mSubjects;
public Course(){} // Default constructor required for calls to DataSnapshot.getValue(Course.class)
public Course(String CourseName){
mCourseName = CourseName;
}
public String getcourseName(){
return mCourseName;
}
public List<Subject> getSubjects(){ return mSubjects; }
}
显然出了点问题,那么什么是data.getValue(Course.class)返回的值? 还是我写错了数据库?
PS:我写的数据库对象手动
应避免在火力堂妹嵌套结构,创建复杂时增加数据检查火力地堡文档https://firebase.google.com/docs/database/android/structure-data –