Table of contents
Drawing Graphics
Painting an image to the JPanel
A GraphicsHandler class instance is passed into the draw method of every class, and is used to paint an image to the engine’s backing JPanel. The engine sets up the GraphicsHandler class instance on creation, and from that point on it is passed down the chain so that it can be used in any draw method in any class that needs to render graphics.
The GraphicsHandler class has many methods, but the following methods are the most commonly used:
- drawRectangle – draws a hollow rectangle to the screen, can optionally set border color and border thickness
- drawFilledRectangle – draws a filled rectangle to the screen, can optionally set border color and border thickness
- drawImage – draws an image to the screen, can optionally flip the image horizontally, vertically, or both
- drawString – draws a text string to the screen
- drawStringWithOutline – draws a text string to the screen with an outline (works decently enough, but it’s not perfect looking)
Most of the time in game, the drawImage method is what will be used:
public void draw(GraphicsHandler graphicsHandler) {
// draw image at specified location
graphicsHandler.drawImage(image, xLocation, yLocation, imageWidth, imageHeight);
// draw image at specified location flipped horizontally
graphicsHandler.drawImage(image, xLocation, yLocation, imageWidth, imageHeight, ImageEffect.FLIP_HORIZONTAL);
}
The ImageEffect enum contains all the image effects that can be applied to an image.
Draw Order
Something important to keep in mind is that the order that graphics are drawn to the JPanel matters, because each graphic is “pasted” on over whatever was there beforehand.
For an in game example, the grass map tiles in the below image are drawn BEFORE the cat image to ensure that the grass does not cover up the cat. This also ensures that every time the cat moves, the grass map tiles continue to stay behind.
