属性更改时 UI 不更新

Question

当我从 MainActivity 更新 LoginViewModel 中的 User 属性时，我的 UI 没有改变。（卡在这个问题上 2 天了，找不到解决方案）我的 User 类扩展了 BaseObservable（添加了 @Bindable 和 notificationPropertyChanged()），但我不知道我还应该做什么。这些是课程：用户：public class User extends BaseObservable {    protected String  userName;    protected String lastName;    public User(String userName, String lastName) {        this.userName = userName;        this.lastName = lastName;        notifyPropertyChanged(BR._all);    }    @Bindable    public String getUserName() {        return userName;    }    public void setUserName(String userName) {        this.userName = userName;        notifyPropertyChanged(BR.userName);    }    @Bindable    public String getLastName() {        return lastName;    }    public void setLastName(String lastName) {        this.lastName = lastName;        notifyPropertyChanged(BR.lastName);    }}视图模型：public class LoginViewModel extends ViewModel {    private User user;    public LoginViewModel() {        user = new User("Pero","Peric");    }    public User getUser() {        return user;    }    public void setUser(User user) {        this.user = user;    }    public String getUserName()    {        return user.getUserName();    }    public void setUserName(String userName)    {        user.setUserName(userName);    }    public String getLastName()    {        return user.getLastName();    }    public void setLastName(String lastName)    {        user.setUserName(lastName);    }}

Answer 1

问题是我：

a)hadnt implement Observerble interface to ViewModel(I susspect that DataBinding 

    adds/removes his listener through that methods)

b)made get methods @Bindable,and notify notifyPropertyChanged() in seters,

c)add property in ViewModel of type PropertyChangeRegistry

d)add notifyPropertyChanged(int fieldID) method

视图模型：

public class LoginViewModel extends ViewModel implements Observable {

    private User user;

    private PropertyChangeRegistry callbacks;

    public LoginViewModel() {

        user = new User("Karlo","maricevic");

        callbacks = new PropertyChangeRegistry();

    }

    public User getUser() {

        return user;

    }

    public void setUser(User user) {

        this.user = user;

    }

    @Bindable

    public String getUserName()

    {

        return user.getUserName();

    }

    public void setUserName(String userName)

    {

        user.setUserName(userName);

        notifyPropertyChanged(BR.userName);

    }

    @Bindable

    public String getLastName()

    {

        return user.getLastName();

    }

    public void setLastName(String lastName)

    {

        user.setUserName(lastName);

    }

    @Override

    public void addOnPropertyChangedCallback(OnPropertyChangedCallback callback) {

        callbacks.add(callback);

    }

    @Override

    public void removeOnPropertyChangedCallback(OnPropertyChangedCallback callback) {

        //callbacks.remove(callback);

    }

    void notifyPropertyChanged(int fieldId)

    {

        callbacks.notifyCallbacks(this,fieldId,null);

    }

}

PS：在这个例子的小实验之后，你不需要用户扩展 BaseObservable 来从 ViewModel 更新 UI