Re: GWT RC2 with Polymer: Issue while calling click handler from Java.

On Wednesday, October 5, 2016 at 12:59:29 PM UTC+2, GAURAV GUPTA wrote:

Hi All,

I am using below code for creating my custom element, 

package com.test;

import jsinterop.annotations.JsConstructor;

import jsinterop.annotations.JsMethod;

import jsinterop.annotations.JsType;

import com.google.gwt.event.dom.client.ClickEvent;

import com.google.gwt.event.dom.client.ClickHandler;

import com.google.gwt.user.client.Window;

import com.google.gwt.user.client.ui.Button;

@JsType(namespace = "ctb")

public class CustomGWTButton{

@JsConstructor

public CustomGWTButton() {

}

@JsMethod

public Button getButton(){

//#1 java handler not working

return new Button("Test11", new ClickHandler() {

@Override

public void onClick(ClickEvent event) {

Window.alert("How are you?");

}

});

}

}

<link rel="import" href="bower_components/paper-button/paper-button.html"/>

<dom-module id="gwt-button">

<style>

</style>

<template>

<h1>Hello</h1>

<div id="buttonId"/>

</template>

<script>

Polymer({

is: "gwt-button",

attached: function(){

var obj = new ctb.CustomGWTButton();

var button = obj.getButton();

//#2 not working 

button.onclick = function(){

alert('Not Working Fine!!');

}

var line = document.createElement("p");

line.innerHTML = button;

document.getElementById("buttonId").appendChild(line);

//when I do like this, it is working

var ch = line.childNodes[0];

ch.onclick = function(){

alert('Working Fine!!');

}

}

});

</script>

</dom-module>

Below issues I am facing (RED COLOR handlers not working):

1. Click handler defined in java class not working (#1).

This is because the widget is never "attached", so the event handler is never actually added (sinkEvents is not called).

See http://googlewebtoolkit.blogspot.fr/2009/05/widget-best-practices-widget-building.html for example about the widgets lifecycle.

 

2. Then I tried to add onclick in javascript (#2) but it also didnt worked for me.

This is because 'button' is a Button widget, not a <button> DOM element (HTMLButtonElement in JS).

 

3. then I again added onclick Handler in javascrpt (#3), It worked for me. 

This is because when you did line.innerHTML=button it called the button's toString(), which happens to be calling toString() on its underlying HTMLButtonElement DOM element, which will end up as something like <button type="button">Test11</button>.

When getting that element (which will not be the button backing the Button widget in your CustomGWTButton class, but a new one, a copy with the same HTML representation), you can now add a click handler, as it'll be an HTMLButtonElement DOM element.

 

Can you please help me, How I can make work java handler #1 and #2 handler here.

Easiest would be to not mix widgets and non-widgets (DOM elements), and use Elemental or JSNI or JsInterop or whatever to attach an event listener for the click event.

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