I need to create a loop which draws rectangles in a vertical line with alternating color (e.g. black, white, black, white). Can anyone tell me how this is done?
I have tried numerous ways but can't seem to get the loop to work, thanks.
for (int x = 0; x>10;x++) {
int y= 180;
graph2D.drawRect(170, y, 20, 50);
y = y + 45;
}
This is what I have, it won't draw the rectangles for some reason and I cant get it to alternate colors.
You've got a few issues here.
Your for loop will not perform any iterations, as your condition is x > 10 instead of x < 10.
Change the first line from:
for (int x = 0; x>10;x++){
To:
for (int x = 0; x < 10; x++) {
Also, you reset y to 180 every iteration, so once your loop does start, all of the rectangles will be drawn on top of each other. Declare y outside of the loop, or use x to calculate the rectangles position.
Either like this:
int y = 180;
for (int x = 0; x < 10; x++) {
graph2D.drawRect(170, y, 20, 50);
y = y + 45;
}
Or like this:
for (int x = 0; x < 10; x++) {
graph2D.drawRect(170, (x * 45) + 180, 20, 50);
}
The above math (x * 45) + 180 is a super simple way of saying that the first rectangle will be at (x * 45) + 180 = 0 + 180 = 180, the second will be at (x * 45) + 180 = 45 + 180 = 225 and so on and so on.
To change the color of the rectangles, you'll need to make a list or array of Colors, and use a different Color from the list, in each iteration.
//Make the list
Color[] colors = {Color.black, Color.blue, Color.cyan, Color.darkGray,
Color.green, Color.lightGray, Color.magenta, Color.magenta,
Color.orange, Color.pink, Color.red, Color.white, Color.yellow};
//Draw each rectangle
for (int x = 0; x < 10; x++) {
//Change the color
g.setColor(colors[x]);
//Draw the rectangle
graph2D.drawRect(170, (x * 45) + 180, 20, 50);
}
Of course if you want the colors to be random, you can look into using the Random class, and generating a random number between 0 and the length of your colors array. Also note that I use x as an index for the colors array, and if your loop increments x to be higher than the number of colors in the array, you'll get an ArrayIndexOutOfBoundsException.
I also assumed you named your instance of Graphics as g, since it is done that way most of the time.
fillRect rather than drawRect. It takes the same parameters as drawRect so all you have to do is change the name.Why do you use the y variable instead of x that you are looping though?
@Override
public void paint(Graphics graph2D) {
for (int y=0; y<10; y++) {
int height = 50;
if (y%2==0) {
graph2D.setColor(Color.white);
} else {
graph2D.setColor(Color.black);
}
graph2D.fillRect(170, 180 + y*height, 20, 50);
}
}
Also mind the difference while drawing a rectangle:
.drawRect(..) draws the border of a rectangle..fillRect(..) draws the rectangle itself.In case you want to switch between black and white color, change the color with every loop. Every even number y%2 == 0 of loop will have the one color, otherwise the second one (also mentioned in the code above):
if (y%2==0) {
graph2D.setColor(Color.white);
} else {
graph2D.setColor(Color.black);
}
static final int may be slightly better than simply int - it is a compile-time constant, better not leave it to the JVM to recognize that.height, the loop variable is not a compile time constant of course :)
yeach time you enter the loop so the squares are drawing on top of each other. Try movingint y = 180;before the loop and see what you get. From there you can work on colors and the restString color = x%2 == 0 ? "black" : "white". Something like that with color changes.