listView原理记录

转载自：[url]https://blog.csdn.net/guolin_blog/article/details/44996879[/url]


-listView和adapter是为了解耦，一个负责视图，一个负责数据绑定
-listView通过RecycleBin来不断填充可见item，以及循环废弃item。
-AbsListView的onlayout来实现绘制item。ListView的onlayout根据dataChanged是否数据有更新，进行对可见item的填充。
-填充可见item时，

View obtainView(int position, boolean[] isScrap) {
	isScrap[0] = false;
	View scrapView;
	scrapView = mRecycler.getScrapView(position);
	View child;
	if (scrapView != null) {
		child = mAdapter.getView(position, scrapView, this);
		if (child != scrapView) {
			mRecycler.addScrapView(scrapView);
			if (mCacheColorHint != 0) {
				child.setDrawingCacheBackgroundColor(mCacheColorHint);
			}
		} else {
			isScrap[0] = true;
			dispatchFinishTemporaryDetach(child);
		}
	} else {
		child = mAdapter.getView(position, null, this);
		if (mCacheColorHint != 0) {
			child.setDrawingCacheBackgroundColor(mCacheColorHint);
		}
	}
	return child;
}

会跟根据是否有废弃的item，来传给adapter是否可有convertView利用

-之后每次onlayout时，detachAllViewsFromParent将所有item解绑，填充好可见item后，再绑定


[img]http://dl2.iteye.com/upload/attachment/0130/2974/ae862947-5507-3f41-985f-1b20486cb207.png[/img]