Android-将dp单位转换为像素单位，系数为0.5f

Question

我读了here关于将 dp 单位转换为像素单位。但我无法理解 0.5f。这个数字从哪里来，有什么用？

// The gesture threshold expressed in dp
private static final float GESTURE_THRESHOLD_DP = 16.0f;

// Get the screen's density scale
final float scale = getResources().getDisplayMetrics().density;
// Convert the dps to pixels, based on density scale

mGestureThreshold = (int) (GESTURE_THRESHOLD_DP * scale + 0.5f);

// Use mGestureThreshold as a distance in pixels...

Answer 1

将 float 转换为整数会使它们下降。那个 0.5f 是四舍五入的数字:

x = (int) 3.9
print x // 3



x = (int) 3.9 + 0.5f
print x // 4