Using the Timer Control

Using the Timer Control

The Timer control allows you to execute event-handling code repeatedly in defined intervals. The code will be executed on the same thread that the Windows code is running in. If you need code to run in a thread outside of the Windows thread, then you should use the System.Threading namespace.

The Timer control fires by raising a Tick event. A Tick event is raised only when the Timer 's Enabled property is set to true. You can stop a Timer control from firing by setting the Enabled property to false. The Timer control's Interval property defines the number of milliseconds between Tick events.

SHOP TALK: TRAPPING THE TAP-AND-HOLD EVENT

Pocket PC substitutes the tap-and-hold movement in place of the right mouse click. The tap-and-hold movement is simulated by placing the stylus on the screen and holding it in place. A control's ContextMenu control is activated this way.

You may want to respond to a tap-and-hold in other ways beyond bringing up a ContextMenu . To do this, you must use a little creativity. First create a Timer control whose interval is set to the amount of time a user would have to hold the stylus to the screen before triggering the tap-and-hold functionality. Then capture the MouseDown event on the control that will be handling the tap-and-hold event. In the MouseDown event, enable the Timer. Next trap the MouseUp event and disable the Timer in handle. Finally, in the Timer's Tick event handler, perform the action activated by the tap-and-hold event. The following code demonstrates how to handle the three events described above:

 C# private void Form1_MouseDown(object sender,         System.Windows.Forms.MouseEventArgs e) {   timer1.Enabled = true; } private void Form1_MouseUp(object sender,         System.Windows.Forms.MouseEventArgs e) {   timer1.Enabled = false; } private void timer1_Tick(object sender, System.EventArgs e) {   label2.Text = string.Format("Message: {0}", "Hello, World!"); } VB private sub _Form1_MouseDown(sender as object,         e As System.Windows.Forms.MouseEventArgs) _         Handles form1.MouseDown   timer1.Enabled = true End Sub private sub _Form1_MouseUp(sender as object,         e As System.Windows.Forms.MouseEventArgs) _         Handles form1.MouseMove   timer1.Enabled = false End Sub private sub _timer1_Tick(sender as object,         e As System.Windows.Forms.MouseEventArgs) _         Handles timer1.Tick   label2.Text = string.Format("Message: {0}", "Hello, World!") End Sub 

In the "Programming the ProgressBar Control" section, the BombSquad.exe game was presented. The object of the game was to click the Diffuse button before the ProgressBar control filled up. The trick was that the Diffuse button's location would continuously change, while the ProgressBar 's value increased. This application uses two timers. One Timer control determined how often the ProgressBar 's value was updated. And another Timer control handled moving the Diffuse button around the form. Listing 3.4 demonstrates how these two Timer s are handled.

Listing 3.4

 C# private void timerButtonMove_Tick(object sender, System.EventArgs e) {   if(!gameOver) {     this.button1.Location =       new Point(rand.Next(0, 168), rand.Next(0, 216));   }else {     EndGame();   } } private void timerProgressBar_Tick(object sender, System.EventArgs e) {   if( counter < 60 ) {     if( gameOver )       return;     if(this.progressBar1.Value < this.progressBar1.Maximum)       this.progressBar1.Value += 1;       ++counter;   } else {     if( !gameOver ) {       EndGame();       MessageBox.Show("Boom!", "Loser");     }   } } private void EndGame() {   this.timerButtonMove.Enabled = false;   this.timerProgressBar.Enabled = false;   counter = 0;   this.gameOver = true;   this.button2.Enabled = true; } VB Private Sub timerButtonMove_Tick(ByVal sender As Object,         ByVal e As System.EventArgs) _ Handles timerButtonMove.Tick   If Not gameOver Then     Me.button1.Location = _       New Point(rand.Next(0, 168), rand.Next(0, 216))   Else     EndGame()   End If End Sub Private Sub timerProgressBar_Tick(ByVal sender As Object,         ByVal e As System.EventArgs) _ Handles timerProgressBar.Tick   If counter < 60 Then     If gameOver Then       Return     End If     If Me.progressBar1.Value < Me.progressBar1.Maximum Then       Me.progressBar1.Value = Me.progressBar1.Value + 1       counter = counter + 1     Else       If Not gameOver Then         EndGame()         MessageBox.Show("Boom!", "Loser")       End If     End If   End If End Sub Private Sub EndGame()   Me.timerButtonMove.Enabled = False   Me.timerProgressBar.Enabled = False   counter = 0   Me.gameOver = True   Me.button2.Enabled = True End Sub