回调Lambda表达式+ JavaFX [英] Call Back Lambda Expressions + JavaFX

问题描述

因此，我试图更新我的旧JavaFX应用程序之一，该应用程序是在Java 6 Release上创建的.给了我一个提示，我可以转换当前代码并改用lambda表达式，有人可以帮助我在此处转换这段代码，或者以某种方式指导我吗?

So, I am trying to renew one of my old JavaFX applications which were created upon Java 6 Release. I was given a tip that I could convert this current code and use lambda expressions instead, could someone help me convert this piece of code here or somehow guide me?

// define a simple boolean cell value for the action column so that the column will only be shown for non-empty rows.
    addColumn.setCellValueFactory(new Callback<TableColumn.CellDataFeatures<UserDetails, Boolean>, ObservableValue<Boolean>>() {
        @Override public ObservableValue<Boolean> call(TableColumn.CellDataFeatures<UserDetails, Boolean> features) {
            return new SimpleBooleanProperty(features.getValue() != null);
        }
    });

    // create a cell value factory with an add button for each row in the table.
    addColumn.setCellFactory(new Callback<TableColumn<UserDetails, Boolean>, TableCell<UserDetails, Boolean>>() {
        @Override public TableCell<UserDetails, Boolean> call(TableColumn<UserDetails, Boolean> personBooleanTableColumn) {
            return new AddPersonCell(window, tableUser);
        }
    });

推荐答案

Lambda表达式仅在交互中只有一个抽象方法时才起作用.由于Callback就是这种情况，因此这里可以是一个.

Lambda expressions only work, if there is a single abstract method in the interfact. Since this is the case for Callback this can be one here.

基本上，您将匿名类放置为具有(<parameters>) -> <method body>形式的lambda表达式.

Basically you place the anonymus class with a lambda expression of the form (<parameters>) -> <method body>.

在这种情况下

new Callback<TableColumn.CellDataFeatures<UserDetails, Boolean>, ObservableValue<Boolean>>() {
    @Override public ObservableValue<Boolean> call(TableColumn.CellDataFeatures<UserDetails, Boolean> features) {
        return new SimpleBooleanProperty(features.getValue() != null);
    }
}

成为

(TableColumn.CellDataFeatures<UserDetails, Boolean> features) -> {
    return new SimpleBooleanProperty(features.getValue() != null);
}

这可以进一步简化:

1. 如果不需要参数类型来确定要调用的方法，则可以将其删除.
2. 如果只有一个参数没有类型，则可以删除()括号.
3. 如果方法主体仅包含一个语句，则可以删除{}和;.如果该语句是return语句，则也需要删除return关键字.

1. If the parameter types are not needed to decide the method to be called, they can be removed.
2. If there is only a single parameter without a type, the () brackets can be removed.
3. If the method body contains only a single statement, the {} and the ; can be removed. If the statement is a return statement, the return keyword needs to be removed too.

这使您可以进一步将lambda表达式简化为

This allows you to further simplify the lambda expression to

features -> new SimpleBooleanProperty(features.getValue() != null)

---

使用相同的方法

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Using the same approach

new Callback<TableColumn<UserDetails, Boolean>, TableCell<UserDetails, Boolean>>() {
    @Override public TableCell<UserDetails, Boolean> call(TableColumn<UserDetails, Boolean> personBooleanTableColumn) {
        return new AddPersonCell(window, tableUser);
    }
}

可以更改为

personBooleanTableColumn -> new AddPersonCell(window, tableUser)

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