Swift中的按位移位与Java不同

Question

I am trying to shift RGB to a ColorInt like in Java.

Java: The code below returns '-16777216' for a black color.

int a = 255;
int r = 0;
int g = 0;
int b = 0;

int hcol = 0;
hcol |= (a & 0xFF) << 24;
hcol |= (r & 0xFF) << 16;
hcol |= (g & 0xFF) << 8;
hcol |= b & 0xFF;
System.out.println(hcol);

Swift: From what I know this should be the same exact code as the Java example. But it is returning only positive numbers and is '0' for black where '16777216'(not a negative) is white.

let a = 255
let r = 0;
let g = 0;
let b = 0;

var colInt = 0;
//colInt |= (a & 0xFF) << 24; (Adding this makes the variable even bigger)
colInt |= (r & 0xFF) << 16;
colInt |= (g & 0xFF) << 8;
colInt |= (b & 0xFF);

print("\(colInt)");

As you can see in the Swift example I don't have the alpha color. If I add that it just makes the colInt an even higher number than the max amount of colors in the RGB spectrum.

Answer 1

You are most likely running on a 64-bit machine so the swift Int type is actually 64-bit, while java int is always 32-bit. That "higher number" you see ( 4278190080 ) is actually 0x00000000FF000000 in 64-bit integer. Using Int32 should yield your expected result.

let a : Int32 = 255
let r : Int32 = 0;
let g : Int32 = 0;
let b : Int32 = 0;

var colInt : Int32 = 0;
colInt |= (a & 0xFF) << 24;
colInt |= (r & 0xFF) << 16;
colInt |= (g & 0xFF) << 8;
colInt |= (b & 0xFF);

print("\(colInt)");    //-16777216