ImageButton in gwt

Question

I have to create a image button in gwt which uses three images(left side image,center stretch image and right image).Left side images and right images having rounded corners.Center Image wants to be stretched depends on button title size.Created ImageButton should have all the functionalities of Button.

Can anyone help me in how to achieve this.

Answer 1

If you need a button with rounded corners then there are a number of options:

1. Create a new widget that extends the DecoratorPanel to create the rounded corners. The DecoratorPanel will result in a table (HTML). You'll probably want to replace the standard images. Look at the standard.css that GWT provides to find the styles that define those images, then override those styles in your custom stylesheet (look for the CSS class ".gwt-DecoratorPanel"). In the widget, add a Label widget to display the button text and provide get and set methods on your widget to get and set text to the internal label. The label will resize automatically forcing the table cell to grow bigger.

2. Create a new widget that extends Composite. The widget should wrap a FlexTable. Use 3 cells on the same row. Add a Label to the center cell and provide get and set methods on your widget to get and set text to the internal label. The label will resize automatically forcing the table cell to grow bigger. Add the appropriate handlers to the FlexTable widget. I suggest you use those events to add or remove styles to the appropriate cells and define the background images in a stylesheet.

3. You could create your own widget. This requires that you generate your own HTML etc. which may not immediately work in every browser. I recommend trying option 1 or 2 first.

Answer 2

You might be able to get away with using only one sprite image if you can limit the maximum width of your buttons. We wrote a CssButton class (extends Button) as part of the GWT Portlets framework that uses a single background image sprite to create rounded buttons. The code uses CSS clipping to select the correct background image from the sprite based on the width of the button.

The main advantages are that it extends the normal GWT Button and uses only a single BUTTON element in the DOM (lightweight). The disadvantage is that the maximum width of the button is limited to the widest button image in the sprite.

It also handles rollover and click effects all using the same sprite.

The code is in the GWT Portlets repository if you want to look further.