- XNA 4.0 Game Development by Example Beginner's Guide（Visual Basic Edition）
- Kurt Jaegers
- 194字
- 2021-08-20 15:50:42
Time for action – falling pieces
- Add a new class to the Flood Control project called
FallingPiece. - Add the
Inheritsline after the class declaration as follows:Inherits GamePiece
- Add the following declarations to the
FallingPiececlass:Public VerticalOffset As Integer Public Shared FallRate As Integer = 5
- Add a constructor for the
FallingPiececlass:Public Sub New(type As String, verticalOffset As Integer) MyBase.New(type) Me.VerticalOffset = verticalOffset End Sub - Add a method to update the piece:
Public Sub UpdatePiece() VerticalOffset = CInt(MathHelper.Max(0, VerticalOffset - FallRate)) End Sub
What just happened?
Simpler than a RotatingPiece, a FallingPiece is also a child of the GamePiece class. A FallingPiece has an offset (how high above its final destination it is currently located) and a falling speed (the number of pixels it will move per update).
As with a RotatingPiece, the constructor passes the type parameter to its base class constructor, and uses the verticalOffset parameter to set the VerticalOffset member. Again, we use the Me. notation to differentiate the two identifiers of the same name.
Lastly, the UpdatePiece() method subtracts FallRate from VerticalOffset, again using the MathHelper.Max() method to ensure that the offset does not fall below zero.