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POIn gridview adapter, getView(position == 0) was invoked too many times to measure layout when setImageBitmap() in a loader
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  1. POIn gridview adapter, getView(position == 0) was invoked too many times to measure layout when setImageBitmap() in a loader
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    copied!<p>I have a <code>GridView</code> for showing some icons.</p> <p>BEFORE I had read this <a href="http://developer.android.com/training/displaying-bitmaps/index.html" rel="nofollow noreferrer">Displaying Bitmaps Efficiently</a> from Android developer site, I was decoding bitmap from local path directly in <code>getView()</code> of adapter, like this :</p> <pre><code>public View getView(int position, View convertView, ViewGroup parent) { ... ImageView icon = ...... (from getTag() of convertView) icon.setImageBitmap(BitmapUtil.decode(iconPath)); ... } </code></pre> <p>this way works fine anyway, I called it [Direct Mode], the output log for <code>getView()</code> method should be :</p> <pre><code>getView(0) // measure kid's layout. getView(0) getView(1) getView(2) ... getView(n) // when scrolling gridview. getView(n+1) ... getView(n+3) // scrolling again. getView(n+4) ... </code></pre> <p>then I am trying to change the code to [Loader Mode] mentioned in article <a href="http://developer.android.com/training/displaying-bitmaps/index.html" rel="nofollow noreferrer">Displaying Bitmaps Efficiently</a>, as following :</p> <pre><code>public View getView(int position, View convertView, ViewGroup parent) { ... ImageView icon = ...... (from getTag() of convertView) loadIcon(icon, iconPath); ... } </code></pre> <p>in <code>loadIcon()</code> :</p> <pre><code>... final CacheImageLoader loader = new CacheImageLoader(getActivity(), imageView, imageUrl, savePath); final AsyncDrawable asyncDrawable = new AsyncDrawable(getResources(), placeHolderBitmap, loader); imageView.setImageDrawable(asyncDrawable); </code></pre> <p>in Loader's listener :</p> <pre><code>@Override public void onLoadComplete(Loader&lt;Bitmap&gt; arg0, Bitmap arg1) { ... ImageView imageView = imageViewReference.get(); if (result != null &amp;&amp; imageView != null) { imageView.setImageBitmap(result); } } </code></pre> <p>Basically, it is same as the training code, actually, this way works fine as well. However, I found something different, in this mode the <code>getView()</code> method in adapter was invoked too many times, however, these repeat call to this method always with "position" parameter == 0, it means something invoke g<code>etView(0, X, X)</code> repeatedly. </p> <pre><code>getView(0) // measure kid's layout. getView(0) getView(1) getView(2) ... getView(0) // loader completed then imageView.setImageBitmap(result); getView(0) // same as above getView(0) getView(0) ... getView(n) // when scrolling gridview. getView(n+1) getView(n+2) getView(0) // loader completed then imageView.setImageBitmap(result); getView(0) // same as above getView(0) ... getView(n+3) // scrolling again. getView(n+4) getView(0) // loader completed then imageView.setImageBitmap(result); getView(0) // same as above getView(0) </code></pre> <p>It is not good because I am using a loader in <code>getView()</code>. I have checked the source code and found they are originally called by <strong><code>imageView.setImageBitmap(result)</code></strong> in loader's <code>onLoadComplete</code> method, and in <code>ImageView</code> :</p> <pre><code> /** * Sets a drawable as the content of this ImageView. * * @param drawable The drawable to set */ public void setImageDrawable(Drawable drawable) { ... int oldWidth = mDrawableWidth; int oldHeight = mDrawableHeight; updateDrawable(drawable); if (oldWidth != mDrawableWidth || oldHeight != mDrawableHeight) { requestLayout(); } invalidate(); } } </code></pre> <p>here, <strong><code>requestLayout()</code></strong> is View's method and always executes in either [Direct Mode] or [Loader Mode], in View.class :</p> <pre><code>public void requestLayout() { mPrivateFlags |= FORCE_LAYOUT; mPrivateFlags |= INVALIDATED; if (mLayoutParams != null) { mLayoutParams.onResolveLayoutDirection(getResolvedLayoutDirection()); } if (mParent != null &amp;&amp; !mParent.isLayoutRequested()) { mParent.requestLayout(); } } </code></pre> <p>however the difference is: in [Direct Mode], the <code>mParent.requestLayout()</code> is invoked once, but in [Loader Mode], every time when i call <strong><code>imageView.setImageBitmap(result);</code></strong>, the <code>mParent.requestLayout()</code> will be invoked as well, it means <code>mParent.isLayoutRequested()</code> return <code>false</code>, and <code>mParent.requestLayout();</code> will cause the <code>GridView</code> measure its kid's layout by calling <code>obtainView()</code> to first kid and then cause <code>getView(0, X, X)</code> :</p> <pre><code>@Override protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { ... mItemCount = mAdapter == null ? 0 : mAdapter.getCount(); final int count = mItemCount; if (count &gt; 0) { final View child = obtainView(0, mIsScrap); ... </code></pre> <hr> <p>So, my <strong>question</strong> is: why <code>mParent.isLayoutRequested()</code> return <code>false</code> if I am using [loader mode]? or is it just a normal case ? </p>
 

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