a little dirty trick to solvebinding issue

asked 2007-05-29 08:59:03 +0800

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Orignial message at:
https://sourceforge.net/forum/message.php?msg_id=4334430

By: devilgary

I found an issue with data binding as I tried to use data binding with my application.
It's not really a bug but i think it will create headache for us. After struggling couple hours, I found a dirty trick to workaround this problem and would like to share it wit you guys.

Below is snippet of the code

<a:bind value="myBean.text1;save-when:self.onChange"/>
<textbox id="txt1" onChanging="txt2.value = event.value"/>

<a:bind value="myBean.text2;save-when:self.onChange"/>
<textbox id="txt2"/>

Class MyBean just simple get and set methods of txt1 and txt2.

How it works
The code's actually pretty straight forward. Whatever we write in txt1 will be copied to txt2 and save to corresponding attribute in class MyBean.

The issue
What's wrong with this code? Just type something in txt1 then move the cursor on something else. Now, you will see empty value on txt2!!!. It should be there but apparently data binding doesn't occur on txt2. Please note "save-when" can only have single definition of event from java doc.

How to solve
<a:bind value="myBean.text1;save-when:self.onChange"/>
<textbox id="txt1" onChanging="txt2.value = event.value"/>

<a:bind value="myBean.text2;save-when:txt1.onChange"/>
<textbox id="txt2" onChange="myBean.setTxt2(self.value)"/>

Explanation
"save-when:txt1.onChange" => The value of txt2 will be saved as the onChange method was called from txt1 hence this will prevent the empty value issue after lost focus on txt1.

But this is not enough.. This gonna create a new problem. For example, if we modify the value of txt2 the value won't be saved in MyBean.txt2. It will use the value of txt1 instead.

So we need another code to cope that problem =) onChange="myBean.setTxt2(self.value)" => Anything we write/modify in txt2 will be saved in the myBean. Hence all problems are solved now!!

I admit this dirty trick is kinda break the rule for data binding but I couldn't find a better way to workaround it.


Regards,

Gary Purnomosidi