Devi cancellare la scritta vecchia col colore di fondo.
per farlo devi salvare la scritta vecchia e la posizione di stampa
// IMPORTANT: ELEGOO_TFTLCD LIBRARY MUST BE SPECIFICALLY
// CONFIGURED FOR EITHER THE TFT SHIELD OR THE BREAKOUT BOARD.
// SEE RELEVANT COMMENTS IN Elegoo_TFTLCD.h FOR SETUP.
//Technical support:goodtft@163.com
#include <Elegoo_GFX.h> // Core graphics library
#include <Elegoo_TFTLCD.h> // Hardware-specific library
// The control pins for the LCD can be assigned to any digital or
// analog pins...but we'll use the analog pins as this allows us to
// double up the pins with the touch screen (see the TFT paint example).
#define LCD_CS A3 // Chip Select goes to Analog 3
#define LCD_CD A2 // Command/Data goes to Analog 2
#define LCD_WR A1 // LCD Write goes to Analog 1
#define LCD_RD A0 // LCD Read goes to Analog 0
#define LCD_RESET A4 // Can alternately just connect to Arduino's reset pin
// When using the BREAKOUT BOARD only, use these 8 data lines to the LCD:
// For the Arduino Uno, Duemilanove, Diecimila, etc.:
// D0 connects to digital pin 8 (Notice these are
// D1 connects to digital pin 9 NOT in order!)
// D2 connects to digital pin 2
// D3 connects to digital pin 3
// D4 connects to digital pin 4
// D5 connects to digital pin 5
// D6 connects to digital pin 6
// D7 connects to digital pin 7
// For the Arduino Mega, use digital pins 22 through 29
// (on the 2-row header at the end of the board).
// Assign human-readable names to some common 16-bit color values:
#define BLACK 0x0000
#define BLUE 0x001F
#define RED 0xF800
#define GREEN 0x07E0
#define CYAN 0x07FF
#define MAGENTA 0xF81F
#define YELLOW 0xFFE0
#define WHITE 0xFFFF
Elegoo_TFTLCD tft(LCD_CS, LCD_CD, LCD_WR, LCD_RD, LCD_RESET);
// If using the shield, all control and data lines are fixed, and
// a simpler declaration can optionally be used:
// Elegoo_TFTLCD tft;
void setup(void) {
Serial.begin(9600);
Serial.println(F("TFT LCD test"));
#ifdef USE_Elegoo_SHIELD_PINOUT
Serial.println(F("Using Elegoo 2.4\" TFT Arduino Shield Pinout"));
#else
Serial.println(F("Using Elegoo 2.4\" TFT Breakout Board Pinout"));
#endif
Serial.print("TFT size is "); Serial.print(tft.width()); Serial.print("x"); Serial.println(tft.height());
tft.reset();
uint16_t identifier = tft.readID();
if(identifier == 0x9325) {
Serial.println(F("Found ILI9325 LCD driver"));
} else if(identifier == 0x9328) {
Serial.println(F("Found ILI9328 LCD driver"));
} else if(identifier == 0x4535) {
Serial.println(F("Found LGDP4535 LCD driver"));
}else if(identifier == 0x7575) {
Serial.println(F("Found HX8347G LCD driver"));
} else if(identifier == 0x9341) {
Serial.println(F("Found ILI9341 LCD driver"));
} else if(identifier == 0x8357) {
Serial.println(F("Found HX8357D LCD driver"));
} else if(identifier==0x0101)
{
identifier=0x9341;
Serial.println(F("Found 0x9341 LCD driver"));
}
else if(identifier==0x1111)
{
identifier=0x9328;
Serial.println(F("Found 0x9328 LCD driver"));
}
else {
Serial.print(F("Unknown LCD driver chip: "));
Serial.println(identifier, HEX);
Serial.println(F("If using the Elegoo 2.8\" TFT Arduino shield, the line:"));
Serial.println(F(" #define USE_Elegoo_SHIELD_PINOUT"));
Serial.println(F("should appear in the library header (Elegoo_TFT.h)."));
Serial.println(F("If using the breakout board, it should NOT be #defined!"));
Serial.println(F("Also if using the breakout, double-check that all wiring"));
Serial.println(F("matches the tutorial."));
identifier=0x9328;
}
tft.begin(identifier);
tft.fillScreen(BLACK);
}
int posx=0;
int posy=0;
int i=0;
int oldi=0;
int oldx=0;
int oldy=0;
void loop(void) {
unsigned long start = micros();
tft.setCursor(0, 0);
tft.setTextColor(RED);
tft.setTextSize(2);
tft.println("Hello World!");
tft.println(01234.56789);
tft.println(0xDEADBEEF, HEX);
tft.println();
tft.println();
i++;
tft.setTextColor(RED);
tft.print("Variabile I = ");
//qui può iniziare la funzione assegni id nel loop
posx=tft.getCursorX();//salva posx e posy posizione stampa
posy=tft.getCursorY();
tft.setCursor(oldx,oldy);//sulla posizione precedente
tft.setTextColor(BLACK);//colore sfondo cancella
tft.print(oldi);//cancello scritta precedente
tft.setCursor(posx,posy);//posizione scrittura attuale
oldx=tft.getCursorX();//salvo per dopo
oldy=tft.getCursorY();
tft.setTextColor(RED);//Colore scrittura
tft.println(i);//scrivo attuale
oldi=i;//memorizzo per cancellare dopo
//qui la funzione ritorna
delay(1000);
}
per ogni scritta che visualizzi sul display
devi salvare 4 posizioni e il testo vecchio
int Id
int posx(Id)
int posy(Id)
int oldx(Id)
int oldy(Id)
String oldStr(Id)
In ogni punto in cui scrivi sul display chiami una funzione a cui passi l' id
qui salvi posxy
cancelli a oldxy con la scritta old
ti riposizioni a posxy e salvi in oldxy la posizione attuale
salvi la scritta attuale in oldStr / la puoi salvare anche nel loop
torni e stampi / o stampi e torni