How to use Outer Method's input in Anonymous Inner Class?

问题

For Instance how can I use the input 'hasTypedSomeToken' in my Anonymou inner class in the following -

    public class Login {

        void display(boolean hasTypedSomeToken)
        {
           //some code here

               Button btnLogIn = new Button("Login", new ClickHandler() {

                @Override
                public void onClick(ClickEvent event) {

                    if(Login.this.hasTypedSomeToken) //HOW TO USE hasTypedSomeToken HERE 
                    {

                    //do something

                    }
                }
          }
      }

回答1:

The variables declared within a method are local variables. e.g. hasTypedSomeToken and btnLogIn are local variables in your display method.

And if you want to use those variables inside a local inner class (classes that are defined inside a method e.g. the anonymous class that implements ClickHandler in your case) then you have to declare them final.

e.g.

void display(final boolean hasTypedSomeToken) {

If you look at Login.this.hasTypedSomeToken, this is used to access member variables. Local variables are not members of class. They are automatic variables that live only within the method.

回答2:

First of all, you have to make it final:

void display(final boolean hasTypedSomeToken)

Then you can refer to it simply as hasTypedSomeToken:

if (hasTypedSomeToken) ...

回答3:

You need to declare it final, like this void display(final boolean hasTypedSomeToken), and use it without prefixes: if(hasTypedSomeToken).

回答4:

Make the variable final:

public class Login {

    void display(final boolean hasTypedSomeToken) {
        Button btnLogIn = new Button("Login", new ClickHandler() {

            @Override
            public void onClick(ClickEvent event) {

                if (hasTypedSomeToken) {
                    // frob a widget
                }
            }
        });
    }
}

来源：https://stackoverflow.com/questions/8536126/how-to-use-outer-methods-input-in-anonymous-inner-class

标签

java

anonymous-inner-class

outer-classes