I have a datagrid which has 3 columns in main application. In the third column I want to use the item renderer where I want to use hbox which has two components inside it. One is a button and one is a label. I also have a slider in the main application. I want to change the alpha of the button of itemrenderer from the main application file using the slider, where the datagrid is used. I can access the data provider properties inside the item renderer using data property. But how do I access the parent application properties. For this I tried to create custom datagrid and passed the value of slider using data binding. But could not access the property. In a list when I did the same thing, I could access the property using listData property of item renderer, but in case of datagrid I couldn't do so.
how do I access the parent application properties
Generally; I would recommend you don't. An itemRenderer should be able to access all the properties it needs through the data element; which relates to the dataProvider.
It is a break in encapsulation to access properties of components that are higher up in the display hierarchy.
That said, there are a lot of ways to this.
To access the main application you can use FlexGlobals.topLevelApplication to access the top level application.
You can store your slider value as a static variable and access it from the itemRenderer that way.
You could store the slider value in some data/model object and use a Dependency Injection Framework (Such as Swiz or Robotlegs) to inject that data/model object into your itemRenderer.