question about screen resolution on tiledLayer

Java on Mobile Devices J2ME
#1

I am using a tiledLayer, my first design in the scrolling background is that the character is fixed at the center of the screen and when the user presses (hold) down, the screen moves down but the character stays at the center of the screen.

THE QUESTION:
i want my character roam around the screen (meaning he will no longer be at the center of the screen) and when he reaches some point (he is near the edge of the screen) the tiledLayer will move.

eg
|--------------------------------border-----------------------------|
|--------------------------------border-----------------------------|
|--------------------------------border-----------------------------|
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
| -border- | ---------- character can roam here ---------- |-border- |
|--------------------------------border-----------------------------|
|--------------------------------border-----------------------------|
|--------------------------------border-----------------------------|

this represents the screen of the mobile phone.
a part of the tiledLayer is shown here, and when the character reaches the “border” the tiledLayer will move. The character cannot cross that border (actually i think that border should be invincible or imaginary)

I hope I didn’t make myself look stupid here. I hope you can help me. THANKS IN ADVANCE FOR THOSE WHO WILL! ;D

#2

I did a Pacman game in VB with maps that can be larger than the game’s window, and I implemented something like that.

I basically defined 3 regions for the screen: one was the same as the border region you described, the edge of the screen where the player could never reach (unless there was no more map to be scrolled); then I had an inner border, and when the screen started scrolling (because the player had reached the outer border), the scrolling would continue as long as the player was in the inner border; and the center of the window, once the player was in this region all scrolling would stop. When the scrolling started, the screen would move at 1.5 times the speed of the player, and this would insure that the player stayed within the outer border and that when scrolling started the player would reach the inner region even if he kept going towards the edge (he couldn’t outrun the scrolling). The effect was quite nice.

The source code is available here.

The relevant scrolling code is in Engine.bas at the beginning of the PlayGame function:



' this section takes care of scrolling horizontally, there is another similar piece of code that handles the vertical scrolling      
If frmMain.picCanvas.ScaleWidth > frmMain.picView.ScaleWidth Then 
  ' the window is smaller than the map 
  If Pac.X <= CameraX + 50 Then 
    ' the player has reached the outer border, start scrolling 
    HCameraDirection = West
  End If
  If Pac.X >= CameraX + 200 And Pac.X + CellSize <= CameraX + frmMain.picView.ScaleWidth - 200 Then
    ' the player has reached the inner region, stop scrolling 
    HCameraDirection = None
  End If
  If Pac.X + CellSize >= CameraX + frmMain.picView.ScaleWidth - 50 Then 
    ' the player has reached the outer border, start scolling 
    HCameraDirection = East
  End If
                
  Select Case HCameraDirection
    ' note: camera moves faster than player! 
    Case East
      CameraX = CameraX + Pac.Speed * 1.5
    Case West
      CameraX = CameraX - Pac.Speed * 1.5
  End Select
                
  ' special cases for when the borders of the map are reached (the player should be able to move into the edges
  If CameraX > MapWidth * CellSize - frmMain.picView.ScaleWidth Then CameraX = MapWidth * CellSize - frmMain.picView.ScaleWidth
  If CameraX < 0 Then CameraX = 0
Else
  ' the map fits entirely, camera is on 0
  CameraX = 0
End If

I hope that helps.

shmoove