GWT 中的原生 Javascript 方法
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原文地址: http://stackoverflow.com/questions/981924/
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Native Javascript method in GWT
提问by DLH
I have a native Javascript method in one of my GWT Java classes, but I'm having trouble calling my Java methods from the native Javascript code. I tried to follow thisas closely as I could, but I can't get it to work. I compiled it and ran it in Firefox, and the error console said "Error: this.lc is not a function". I tried changing all the methods to public, but that didn't seem to make a difference. What am I doing wrong?
我的一个 GWT Java 类中有一个本机 Javascript 方法，但是我无法从本机 Javascript 代码调用我的 Java 方法。我试图尽可能密切地遵循这一点，但我无法让它发挥作用。我编译它并在Firefox中运行它，错误控制台说“错误：this.lc不是函数”。我尝试将所有方法更改为public，但这似乎没有什么区别。我究竟做错了什么？
package com.proprintsgear.design_lab.client;
...
public class ValueBox extends HorizontalPanel {
...
private void fireChange() {
...
}
private void increaseValue() {
...
}
private native void addNativeMouseWheelListener(String id) /*-{
function mouseOverHandler(e) {
$wnd.addEventListener("DOMMouseScroll", scrollWheelMove, false);
}
function mouseOutHandler(e) {
$wnd.removeEventListener("DOMMouseScroll", scrollWheelMove, false);
}
function scrollWheelMove(e) {
if ($wnd.event || $wnd.Event) {
if (!e) e = $wnd.event;
if (e.wheelDelta <= 0 || e.detail > 0 ) {
$wnd.alert("DOWN");
} else {
[email protected]_lab.client.ValueBox::increaseValue()();
}
[email protected]_lab.client.ValueBox::fireChange()();
}
}
var box=$doc.getElementById(id);
box.addEventListener("mouseout",mouseOutHandler,false);
box.addEventListener("mouseover",mouseOverHandler,false);
}-*/;
采纳答案by rustyshelf
In all the code I've done in the past, I've never used 'this' to identify my class, I have passed the class in.
在我过去完成的所有代码中，我从未使用“this”来标识我的班级，而是将班级传入。
Eg: Change this:
例如：改变这个：
private native void addNativeMouseWheelListener(String id) /*-{
function mouseOverHandler(e) {
$wnd.addEventListener("DOMMouseScroll", scrollWheelMove, false);
}
function mouseOutHandler(e) {
$wnd.removeEventListener("DOMMouseScroll", scrollWheelMove, false);
}
function scrollWheelMove(e) {
if ($wnd.event || $wnd.Event) {
if (!e) e = $wnd.event;
if (e.wheelDelta <= 0 || e.detail > 0 ) {
$wnd.alert("DOWN");
} else {
[email protected]_lab.client.ValueBox::increaseValue()();
}
[email protected]_lab.client.ValueBox::fireChange()();
}
}
var box=$doc.getElementById(id);
box.addEventListener("mouseout",mouseOutHandler,false);
box.addEventListener("mouseover",mouseOverHandler,false);
}-*/;
To this:
对此：
private native void addNativeMouseWheelListener(ValueBox instance, String id) /*-{
function mouseOverHandler(e) {
$wnd.addEventListener("DOMMouseScroll", scrollWheelMove, false);
}
function mouseOutHandler(e) {
$wnd.removeEventListener("DOMMouseScroll", scrollWheelMove, false);
}
function scrollWheelMove(e) {
if ($wnd.event || $wnd.Event) {
if (!e) e = $wnd.event;
if (e.wheelDelta <= 0 || e.detail > 0 ) {
$wnd.alert("DOWN");
} else {
[email protected]_lab.client.ValueBox::increaseValue()();
}
[email protected]_lab.client.ValueBox::fireChange()();
}
}
var box=$doc.getElementById(id);
box.addEventListener("mouseout",mouseOutHandler,false);
box.addEventListener("mouseover",mouseOverHandler,false);
}-*/;
回答by Shannon -jj Behrens
I found a better way. It's similar to what you do in JavaScript, where you set "var that = this". Using this approach, you don't have to pass this to listenForPostMessage():
我找到了更好的方法。它类似于你在 JavaScript 中所做的，在那里你设置“var that = this”。使用这种方法，您不必将其传递给 listenForPostMessage()：
protected native void postMessage(String msg) /*-{
$wnd.postMessage(msg, "*");
}-*/;
private final native void listenForPostMessage() /*-{
var that = this;
$wnd.addEventListener("message", function(msg) {
[email protected]::onPostMessage(Ljava/lang/String;Ljava/lang/String;)(
msg.data, msg.origin);
});
}-*/;
private void onPostMessage(String data, String origin) {
Label msgLabel = new Label();
msgLabel.setText("GWT received a postMessage: Data: " +
data + " Origin: " + origin);
mainPanel.add(msgLabel);
}
