Java 如何使用 lambda 编写新的 ListChangeListener<Item>()？
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How do I write a new ListChangeListener<Item>() with lambda?
提问by simonides
How do I write a new ListChangeListener() with lambda in java8?
如何在 java8 中使用 lambda 编写新的 ListChangeListener()？
listItems.addListener(new ListChangeListener<Item>() {
@Override
public void onChanged(
javafx.collections.ListChangeListener.Change<? extends Item> c) {
// TODO Auto-generated method stub
}
});
This is what I tried:
这是我尝试过的：
listItems.addListener(c->{});
But eclipse states:
但日食指出：
The method addListener(ListChangeListener) is ambiguous for the type ObservableList.
方法 addListener(ListChangeListener) 对于 ObservableList 类型是不明确的。
The List is declared as:
该列表声明为：
ObservableList<Item> listItems = FXCollections.observableArrayList();
采纳答案by Andrew Vitkus
Since ObservableListinherits addListener(InvalidationListener)from the Observableinterface, the compiler is unable to determine which version to call. Specifying the type of the lambda through a cast should fix this.
由于从接口ObservableList继承，编译器无法确定调用哪个版本。通过强制转换指定 lambda 的类型应该可以解决这个问题。addListener(InvalidationListener)Observable
listItems.addListener((ListChangeListener)(c -> {/* ... */}));
You can also explicitly specify the type of c:
您还可以明确指定的类型c：
listItems.addListener((ListChangeListener.Change<? extends Item> c) -> {/* ... */});
回答by dmolony
This code works without having to specify the types.
此代码无需指定类型即可工作。
listView.focusedProperty ().addListener ( (arg, oldVal, newVal) -> System.out
.printf ("ListView %s focus%n", (newVal ? "in" : "out of")));
