Step 4: Retrieving Immediate Data from the Keyboard

Once a device is acquired, your application can start retrieving data from it. The simplest way to do this is to call the DirectInputDevice8.GetDeviceStateKeyboard method, which takes a snapshot of the device's state at the time of the call.

The GetDeviceStateKeyboard method accepts as its single parameter a DIKEYBOARDSTATE type, which simply contains an array of 256 bytes.

The following sample code retrieves the state of the keyboard.

Dim state As DIKEYBOARDSTATE
Call didev.GetDeviceStateKeyboard(state)
 

After retrieving the keyboard's current state, your application may respond to specific keys that were pressed at the time of the call. Each element in the buffer represents a key. If an element's high bit is set equal to 1, the key was pressed at the moment of the call. Otherwise, the key was up. To check the state of a given key, use the constants of the CONST_DIKEYFLAGS enumeration to index the buffer for a given key.

The following sample code shows how an application might move a vehicle around in response to the arrow keys.

If state.Key(DIK_UP) And &H80 Then
  ' Move the vehicle up
End If
if state.Key(DIK_DOWN) And &H80 Then
  ' Move the vehicle down
End If
' And so on.
 

The following form could also be used.

If state.Key(DIK_UP) Then
  ' Move the vehicle up
End If
 

Keep in mind that DIK_UP is a single key, the dedicated up arrow key. DirectInput treats the 8 key on the numerical keypad as a distinct key, and gives it the same identifier regardless of whether NUM LOCK is on. In order to allow input from either of the arrow keys, you would have to write code as in the following sample.

If state.Key(DIK_UP) Or state.Key(DIK_NUMPAD8) Then
  ' Move the vehicle up
End If