Android-Android获取屏幕大小为什么会自动减去状态栏高度

public int getDisplayScreenHeight()
{
int screenHeight = 0;

DisplayMetrics metrics = new DisplayMetrics();
Display display = getWindowManager().getDefaultDisplay();
display.getMetrics(metrics);

int ver = Build.VERSION.SDK_INT;
if (ver < 13)
{
screenHeight = metrics.heightPixels;
}
else if (ver == 13)
{
try {
Method method = display.getClass().getMethod("getRealHeight");
screenHeight = (Integer) method.invoke(display);
} catch (Exception e) {
e.printStackTrace();
}
}
else if (ver > 13)
{
try {
Method method = display.getClass().getMethod("getRawHeight");
screenHeight = (Integer) method.invoke(display);
} catch (Exception e) {
e.printStackTrace();
}
}

return screenHeight;
}