从异步调用运行方法返回一个值

Return a value from asynchronous call to run method(从异步调用运行方法返回一个值)

问题描述

我有一个必须返回布尔值的方法.该方法有一个异步调用 run 方法.在运行方法中，我必须在封闭方法中设置变量.下面是我的代码.

I have a method that has to return a boolean value. The method has an asynchronous call to run method. In the run method, i have to set variable in the enclosing method. below is my code.

private boolean isTrue() {
    boolean userAnswer;
    Display.getDefault().asyncExec(new Runnable() {
        public void run() {
            userAnswer = MessageDialog.openQuestion(new Shell(), "some message", "some question?");
        }
    });
    return userAnswer;
}   

这段代码给出了错误——userAnswer"必须是最终的，如果我把它变成最终的，我就不能给它赋值.请提出一种处理这种情况的方法.

This code gives error -- "userAnswer" has to be final, and if i make it final i cant assign a value to it. Please suggest a way to handle this scenario.

推荐答案

如果需要适配一个Callable，可以使用java.util.concurrent.FutureTask; 到一个 Runnable.

public class UserQuestion implements Callable<Boolean> {

    private String message;
    private String question;

    public UserQuestion(String message, String question) {
        this.message = message;
        this.question = question;
    }

    public Boolean call() throws Exception {
        boolean userAnswer = MessageDialog.openQuestion(new Shell(),
                message, question);
        return Boolean.valueOf(userAnswer);

    }
}

UserQuestion userQuestion = new UserQuestion("some message", "some question?");
FutureTask<Boolean> futureUserAnswer = new FutureTask<Boolean>(userQuestion);
Display.getDefault().asyncExec(futureUserAnswer);
Boolean userAnswer = futureUserAnswer.get();

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