Calling displayable from a canvas class

[Snalk]

Hello, i am having trouble calling the displayable-funcion
in my MIDlet class from a separate class.

I want to trigger either testForm1 or testForm2 (whichever is most easy)
and put it as the current displayable in my MIDlet when pressing LEFT
without using canvas as a subclass in my SchemaMidlet.
How ?

This is a oversimplification of my programs structure:

Code:

class mainCanvas extends Canvas {
	Form testForm1;
	....
 
	public mainCanvas {
		testForm1 = new Form("Hello1");
		....
 
 
	public void paint(Graphics g) {
	....
 
	}
 
	protected void keyPressed(int keyCode) {
 
		if (getGameAction(keyCode) == Canvas.LEFT) {
 
			***HERE I WANT TO CHANGE THE CURRENT DISPLAYABLE***
 
			this.repaint();
		}
	}
}
 
 
public class SchemaMidlet extends MIDlet implements CommandListener {
 
	private mainCanvas schemaCanvas;
	public Display display;
	Form testForm2;
	
	public SchemaMidlet() {
		schemaCanvas = new mainCanvas();
		testForm2 = new Form("Hello2");
	}
 
	protected void startApp() {
		display = Display.getDisplay(this);
		schemaCanvas.setCommandListener(this);
		display.setCurrent(schemaCanvas);
		schemaCanvas.repaint();
	}
 
	public void commandAction(Command c, Displayable s) {
	...
		}
 
 
	protected void destroyApp(boolean unconditional) {
	}
 
	protected void pauseApp() {
	}
}