Update the TFT screen from ChipworkX with new values but how to remove first the old values

NETMF & Gadgeteer
1

Hi, I like to put some values on the screen with LCD.DrawText( X.ToString(),MyFont1,blue,100,20);
X is an int. 1 to 255
It’s okay but if a new value is comming the old is still on the screen so on the end there is a big blue dot on the screen, with LCD.Clear(); the whole screen is to be clear so that is to good.
How can I solve that no all items disappear from the screen? :’(
Thanks

2

Normally, you just write the same text - at the same position - with background color to make it “disappear”.

3

So the background is black and the text color is red then I I write "LCD.DrawText( X.ToString(),MyFont1,red,100,20); like this.

4

If you wrote it the first time with red, then you write it the second time with black - the background color.

5

Hereby an examply code:


for (i = 10; i < 200; i += 4)
            {
                LCD.DrawText(i.ToString(), MyFont1, Colors. Red, 250, 175);
                LCD.Flush();
                Thread.Sleep(50);
                LCD.DrawText("     ", MyFont1, Colors.Black, 250, 175);
                //LCD.Clear();
                LCD.Flush();
                Thread.Sleep(22);
            }

But nothing change, same big Red dot.

6

You must clear the lcd bitmap before the second drawtext

7

If you just want to remove that dot, write a dot in black over it. Drawing just a space will do nothing… spaces are not visible

8

I use now this code and it’s help but now the total TFT Display is clear.


LCD.Clear();
            int i;
            for (i = 1; i < 20; i += 1)
            {
                LCD.DrawText(i.ToString(), MyFont1, Colors.Orange, 250, 175);
                LCD.Flush();
                Thread.Sleep(50);
               
                LCD.Clear();
                LCD.Flush();
                Thread.Sleep(22);
            }
            
            Thread.Sleep(-1);
9

Now replace LCD.Clear with:


LCD.DrawText(i.ToString(), MyFont1, Colors.Black, 250, 175);
10

This is better, DrawText “Value” is not blinking and variable i is running from 1 to 200 :smiley:


LCD.Clear();
            while (true)
            {
                int i;
                for (i = 1; i < 200; i += 1)
                {                                                //Hor, Vert
                    LCD.DrawText("Value =", MyFont1, Colors.Green, 150, 175);
                    LCD.DrawText(i.ToString(), MyFont1, Colors.Orange, 250, 175);
                    LCD.Flush();
                    Thread.Sleep(500);

                    LCD.Clear();
                    LCD.DrawText("Value =", MyFont1, Colors.Green, 150, 175);
                    LCD.Flush();
                    Thread.Sleep(1);
                }

                i = 0;

                Thread.Sleep(25);
            }
        }
    }
11

But the point is, as was pointed out, if you don’t want to flush the screen (if you have a lot of other text for instance) then all you really need to do is replace the coloured text with the black text (same as background)

LCD.Clear();
int i;
LCD.DrawText("Value =", MyFont1, Colors.Green, 150, 175);
for (i = 1; i < 20; i += 1)
{
LCD.DrawText(i.ToString(), MyFont1, Colors.Orange, 250, 175);
LCD.Flush();
Thread.Sleep(50);

LCD.DrawText(i.ToString(), MyFont1, Colors.Black, 250, 175);
LCD.Flush();
Thread.Sleep(22);
}

oh look at that, code in a code block.

The above means you only write the placeholder text once not every loop

12

Or you could just draw a rect over the region w the proper backcolor…

13

What do you mean about "draw a rect over the region w the proper backcolor…"
Please make an example code.
Thanks

14

Hi Brett,
It’s run now better. The Text "Value = " is clear on the TFT screen and var. i change very nice.
thanks ;D