Manage A Drawing Area - Blackberry JAVA DEVELOPMENT ENVIRONMENT - - DEVELOPMENT GUIDE Manual

Development Guide
MainScreen mScreen = new MainScreen(DEFAULT_MENU | DEFAULT_CLOSE);

Manage a drawing area

The Graphics object represents the entire drawing surface that is available to the BlackBerry® device application. To limit
this area, divide it into XYRect objects. Each XYPoint represents a point on the screen, which is composed of an X co-
ordinate and a Y co-ordinate.
1. Import the following classes:
• net.rim.device.api.ui.Graphics
• net.rim.device.api.ui.XYRect
• net.rim.device.api.ui.XYPoint
2. Create an instance of an XYPoint object and an XYRect object.
XYPoint bottomRight = new XYPoint(50, 50);
XYRect rectangle = new XYRect(topLeft, bottomRight);
XYPoint topLeft = new XYPoint(10, 10);
3. Invoke Graphics.pushContext() to make drawing calls that specify that the region origin should not adjust the
drawing offset. In the following code sample, we create two XYPoint objects to represent the top left and bottom right
points of a rectangle. We then create a rectangular clipping region by creating an XYRect object using the XYPoint
objects. We invoke Graphics.pushContext() to push the rectangular clipping region to the context stack. We
invoke Graphics.drawRect() to draw a rectangle and invoke Graphics.fillRect() to fill a rectangle. We
invoke Graphics.popContext() to pop the current context off of the context stack.
XYPoint bottomRight = new XYPoint(50, 50);
XYPoint topLeft = new XYPoint(10, 10);
XYRect rectangle = new XYRect(topLeft, bottomRight);
graphics.pushContext(rectangle, 0, 0);
graphics.fillRect(10, 10, 30, 30);
graphics.drawRect(15, 15, 30, 30);
graphics.popContext();
graphics.drawRect(15, 15, 30, 30);
graphics.pushContext(rectangle, 0, 0);
graphics.fillRect(10, 10, 30, 30);
graphics.drawRect(15, 15, 30, 30);
graphics.popContext();
graphics.drawRect(15, 15, 30, 30);
4. Invoke pushRegion() and specify that the region origin should adjust the drawing offset. In the following code sample,
we invoke Graphics.drawRect() to draw a rectangle and invoke Graphics.fillRect() to fill a rectangle.
We invoke Graphics.popContext() to pop the current context off of the context stack.
Screens
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