Question

我对GWT有一个不寻常的问题。我在浏览器上编译项目后运行它来运行.html文件。它运行正常，直到出现以下代码行：

public static ClickHandler addBoardButtonHandler(final String name) {
    return new ClickHandler(){

        @Override
        public void onClick(ClickEvent event) {
            Window.alert("We will retrieve them!"); //this line runs
            String boardSTickets = getBoardSTickets(name); // this too
            Window.alert("We got tickets!"); // the code is never executing this line
            String boardSSwimlanes = getBoardSSwimlanes(name);
            Window.alert("We got swimlanes!");
            KanbanizerClient.showSingleBoard(boardSTickets, boardSSwimlanes);
        }

    };
}

此方法由另一种方法调用：

private static Button addBoardButton(String name) {
    Button button = new Button(name);
    button.addClickHandler(HandlerManager.addBoardButtonHandler(name));
    return button;
}

哪个也正常运行。这是getBoardSTickets（）方法：

protected static String getBoardSTickets(String name) {
    final List<String> ticketsJSON = new LinkedList<String>();  
    try {
            Request request = Builder.createBuilder(RequestBuilder.GET, "http://localhost:8080/Kanbanizer/boards/" + name + "/tickets").sendRequest(null, new RequestCallback(){

                @Override
                public void onResponseReceived(Request request,
                        Response response) {
                    if(response.getStatusCode() == 200){
                        ticketsJSON.add(response.getText());
                    }

                }

                @Override
                public void onError(Request request, Throwable exception) {
                    // TODO Auto-generated method stub

                }

            });
        } catch (RequestException e) {
            // TODO Auto-generated catch block
            e.printStackTrace();
        }
    return ticketsJSON.get(0);
}

谢谢：）

Answer 1

了解GWT环境中的ajax - 请阅读https://developers.google.com/web-toolkit/doc/latest/tutorial/clientserver

中的“拨打异步电话”部分

将getBoardSTickets（）编程为执行异步请求调用后返回字符串的方法是有缺陷的。不要尝试在getBoardSTickets（）中返回异步调用的结果。

在return ticketsJSON.get(0);之后立即调用

sendRequest()。它会引发异常，因为ticketJSON将没有条目，因为RequestCallback（）不会完成处理。

尝试从外部传递回调

protected static String getBoardSTickets(String name,  RequestCallback callback){
      //Code for making request
}

您的调用代码应更改为

getBoardSTickets(name, new RequestCallback(){
  //onSuccess and onFailure handling.
} )

对于调用异步调用服务器的所有方法，同样的逻辑也适用。您不应该编程以从方法返回请求响应的值。

GWT突然停止执行

1 个答案: