之前recyclerview中有imageview，会通过glide对其设置图片，但是有的可能没有图片，就必须显示默认图片，在imageview中设置了默认resId资源，但是在进行删除部分item操作后，显示默认图片的会变空白，因此在onBindViewHolder中添加设置，没有图片时添加一个默认图片，用的是holder.headImg.setBackground的方法，然后删除图片的item后就正常了（全部默认图片情况下）...
就这么结束了吗，但是但是，一开始是glide图片的item，默认图片item，删除glide图片的item，结果，默认图片竟然变成了被删除的item的图片，一开始很自然的想当然应该是recyclerview的item复用问题，但是每次onBindViewHolder都会设置啊，然后单选全选，列表中又出现了很诡异的事情，选中带glide图片item，再选默认图片的item，默认图片全被替换成了glide图片，神马情况...
是imageview加tag吗？glide加了tag报错啊...我还尝试了（微笑脸，try catch让我勇往直前），然后还尝试将imageview资源用setImageDrawable（null）设置后再setBackground，然而现象朝着更加诡异的方法发展，单选glide图片变成了默认或者默认图片变glide加载图片 ...
最后的最后，将setBackground改为setImageDrawable/setImageResource，然后问题解决了...改完感觉自己...
心好累啊，使用imageview的setImageDrawable直接绘制多好，简单粗暴；view的setBackground各种判断，最终可能还没法重绘制，导致图片错位复用，平时还是得多看源码。
×××××
上次修改后，由发现进入的时候，某些默认图片会显示设置图片，明明显示的并没有资源，什么鬼...我怀疑和glide有关系，pic有资源用glide给imageView加载，没有的话直接用imageview设置本地res文件，然后将pic为空时，也用glide来设置，Glide.with(context).load(R.drawable.ic_person).into(holder.headImg);显示正常，之前出现的异常现象也ok。
ImageView的setImageDrawable，setImageResource方法
public void setImageDrawable(@Nullable Drawable drawable) {
if (mDrawable != drawable) {
mResource = 0;
mUri = null;
final int oldWidth = mDrawableWidth;
final int oldHeight = mDrawableHeight;
updateDrawable(drawable);
if (oldWidth != mDrawableWidth || oldHeight != mDrawableHeight) {
requestLayout();
}
invalidate();
}
}
/**
* Sets a drawable as the content of this ImageView.
* <p class="note">This does Bitmap reading and decoding on the UI
* thread, which can cause a latency hiccup. If that's a concern,
* consider using {@link #setImageDrawable(android.graphics.drawable.Drawable)} or
* {@link #setImageBitmap(android.graphics.Bitmap)} and
* {@link android.graphics.BitmapFactory} instead.</p>
*
* @param resId the resource identifier of the drawable
*
* @attr ref android.R.styleable#ImageView_src
*/
@android.view.RemotableViewMethod(asyncImpl="setImageResourceAsync")
public void setImageResource(@DrawableRes int resId) {
// The resource configuration may have changed, so we should always
// try to load the resource even if the resId hasn't changed.
final int oldWidth = mDrawableWidth;
final int oldHeight = mDrawableHeight;
updateDrawable(null);
mResource = resId;
mUri = null;
resolveUri();
if (oldWidth != mDrawableWidth || oldHeight != mDrawableHeight) {
requestLayout();
}
invalidate();
}
View的setBackground
/**
* Set the background to a given resource. The resource should refer to
* a Drawable object or 0 to remove the background.
* @param resid The identifier of the resource.
*
* @attr ref android.R.styleable#View_background
*/
@RemotableViewMethod
public void setBackgroundResource(@DrawableRes int resid) {
if (resid != 0 && resid == mBackgroundResource) {
return;
}
Drawable d = null;
if (resid != 0) {
d = mContext.getDrawable(resid);
}
setBackground(d);
mBackgroundResource = resid;
}
/**
* Set the background to a given Drawable, or remove the background. If the
* background has padding, this View's padding is set to the background's
* padding. However, when a background is removed, this View's padding isn't
* touched. If setting the padding is desired, please use
* {@link #setPadding(int, int, int, int)}.
*
* @param background The Drawable to use as the background, or null to remove the
* background
*/
public void setBackground(Drawable background) {
//noinspection deprecation
setBackgroundDrawable(background);
}
/**
* @deprecated use {@link #setBackground(Drawable)} instead
*/
@Deprecated
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. setVisible first while we still have the callback set.
*/
if (mBackground != null) {
if (isAttachedToWindow()) {
mBackground.setVisible(false, false);
}
mBackground.setCallback(null);
unscheduleDrawable(mBackground);
}
if (background != null) {
Rect padding = sThreadLocal.get();
if (padding == null) {
padding = new Rect();
sThreadLocal.set(padding);
}
resetResolvedDrawablesInternal();
background.setLayoutDirection(getLayoutDirection());
if (background.getPadding(padding)) {
resetResolvedPaddingInternal();
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;
}
// Set mBackground before we set this as the callback and start making other
// background drawable state change calls. In particular, the setVisible call below
// can result in drawables attempting to start animations or otherwise invalidate,
// which requires the view set as the callback (us) to recognize the drawable as
// belonging to it as per verifyDrawable.
mBackground = background;
if (background.isStateful()) {
background.setState(getDrawableState());
}
if (isAttachedToWindow()) {
background.setVisible(getWindowVisibility() == VISIBLE && isShown(), false);
}
applyBackgroundTint();
// Set callback last, since the view may still be initializing.
background.setCallback(this);
if ((mPrivateFlags & PFLAG_SKIP_DRAW) != 0) {
mPrivateFlags &= ~PFLAG_SKIP_DRAW;
requestLayout = true;
}
} else {
/* Remove the background */
mBackground = null;
if ((mViewFlags & WILL_NOT_DRAW) != 0
&& (mDefaultFocusHighlight == null)
&& (mForegroundInfo == null || mForegroundInfo.mDrawable == null)) {
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);
invalidateOutline();
}
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