Is there any difference between @null Vs transparent(#00000000)
in my layout I set android:background"@color/transparent"
but its showing some other different background color that I used.
when I used null its working fine.
I want to set @null thru programmatic.
how to do?
@null means no background at all (View.getBackground() returns null).
#00000000 means that you got a ColorDrawable as the background which has a fully-transparent color.
I didn't look at the code, but I guess that the framework tests if the ColorDrawable is fully transparent and does not draw it in this case. Otherwise you would have some drawing overhead, making @null the faster choice. Both should look identical, so not sure if this is your underlying isse.
To set the equivalent of @null in code, use View.setBackgroundDrawable(null).
Yes, there is.
@null means no background.#00000000 means add a transparent background.If you will not have a background make it @null it should perform better. To use @null from the code you can try doing:
widget.setBackgroundDrawable(null);
I would say, in most circumstances prefer @null background over @android:color/transparent.
In code, use setBackground(null) which calls a deprecated method setBackgroundDrawable();
If you look at the View.setBackgroundDrawable(), you will notice that if you pass null as background it will set the flags to SKIP_DRAW and that's it. On other hand, if there is a drawable object, it will go through extra process to set up background padding.
Here is the code of setBackgroundDrawable (Note: use setBackground instead of setBackgroundDrawable)
public void setBackgroundDrawable(Drawable background) {
computeOpaqueFlags();
if (background == mBackground) {
return;
}
boolean requestLayout = false;
mBackgroundResource = 0;
/*
* Regardless of whether we're setting a new background or not, we want
* to clear the previous drawable.
*/
if (mBackground != null) {
mBackground.setCallback(null);
unscheduleDrawable(mBackground);
}
if (background != null) {
Rect padding = sThreadLocal.get();
if (padding == null) {
padding = new Rect();
sThreadLocal.set(padding);
}
resetResolvedDrawables();
background.setLayoutDirection(getLayoutDirection());
if (background.getPadding(padding)) {
resetResolvedPadding();
switch (background.getLayoutDirection()) {
case LAYOUT_DIRECTION_RTL:
mUserPaddingLeftInitial = padding.right;
mUserPaddingRightInitial = padding.left;
internalSetPadding(padding.right, padding.top, padding.left, padding.bottom);
break;
case LAYOUT_DIRECTION_LTR:
default:
mUserPaddingLeftInitial = padding.left;
mUserPaddingRightInitial = padding.right;
internalSetPadding(padding.left, padding.top, padding.right, padding.bottom);
}
mLeftPaddingDefined = false;
mRightPaddingDefined = false;
}
// Compare the minimum sizes of the old Drawable and the new. If there isn't an old or
// if it has a different minimum size, we should layout again
if (mBackground == null || mBackground.getMinimumHeight() != background.getMinimumHeight() ||
mBackground.getMinimumWidth() != background.getMinimumWidth()) {
requestLayout = true;
}
background.setCallback(this);
if (background.isStateful()) {
background.setState(getDrawableState());
}
background.setVisible(getVisibility() == VISIBLE, false);
mBackground = background;
if ((mPrivateFlags & PFLAG_SKIP_DRAW) != 0) {
mPrivateFlags &= ~PFLAG_SKIP_DRAW;
mPrivateFlags |= PFLAG_ONLY_DRAWS_BACKGROUND;
requestLayout = true;
}
} else {
/* Remove the background */
mBackground = null;
if ((mPrivateFlags & PFLAG_ONLY_DRAWS_BACKGROUND) != 0) {
/*
* This view ONLY drew the background before and we're removing
* the background, so now it won't draw anything
* (hence we SKIP_DRAW)
*/
mPrivateFlags &= ~PFLAG_ONLY_DRAWS_BACKGROUND;
mPrivateFlags |= PFLAG_SKIP_DRAW;
}
/*
* When the background is set, we try to apply its padding to this
* View. When the background is removed, we don't touch this View's
* padding. This is noted in the Javadocs. Hence, we don't need to
* requestLayout(), the invalidate() below is sufficient.
*/
// The old background's minimum size could have affected this
// View's layout, so let's requestLayout
requestLayout = true;
}
computeOpaqueFlags();
if (requestLayout) {
requestLayout();
}
mBackgroundSizeChanged = true;
invalidate(true);
}
