仿淘宝京东商品规格属性选择的最简单实现
仿淘宝京东商品规格属性选择的最简单实现
商城里面的规格选择,网上大部分是自定义控件实现的,显得很是麻烦,而我的实现方式是大家最常用的控件RecyclerView,特点是性能好,简单。废话不多说,先看实现的效果图:
上图效果的实现主要是 RecyclerView和flowlayout(流式布局).
RecyclerView设置最大高度
如图规格多的时候,RecyclerView要有个最大高度,我们设置android:maxHeight="300dp"
是没有效果的,因为RecyclerView没有maxHigh这个属性,那怎么实现这个效果呢?通过查看源码,
@Override
protected void onMeasure(int widthSpec, int heightSpec) {
...
if (mLayout.mAutoMeasure) {
...
// now we can get the width and height from the children.
mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
if (mLayout.shouldMeasureTwice()) {
...
// now we can get the width and height from the children.
mLayout.setMeasuredDimensionFromChildren(widthSpec, heightSpec);
}
} else {
...
}
}
当RecyclerView的LayoutManager#isAutoMeasureEnabled()返回true时,RecyclerView高度取决于children view的布局高度,并非取决于RecyclerView自身的测量高度。
下面是setMeasuredDimensionFromChildren(int widthSpec, int heightSpec)源码
void setMeasuredDimensionFromChildren(int widthSpec, int heightSpec) {
final int count = getChildCount();
if (count == 0) {
mRecyclerView.defaultOnMeasure(widthSpec, heightSpec);
return;
}
int minX = Integer.MAX_VALUE;
int minY = Integer.MAX_VALUE;
int maxX = Integer.MIN_VALUE;
int maxY = Integer.MIN_VALUE;
for (int i = 0; i < count; i++) {
View child = getChildAt(i);
final Rect bounds = mRecyclerView.mTempRect;
getDecoratedBoundsWithMargins(child, bounds);
if (bounds.left < minX) {
minX = bounds.left;
}
if (bounds.right > maxX) {
maxX = bounds.right;
}
if (bounds.top < minY) {
minY = bounds.top;
}
if (bounds.bottom > maxY) {
maxY = bounds.bottom;
}
}
mRecyclerView.mTempRect.set(minX, minY, maxX, maxY);
setMeasuredDimension(mRecyclerView.mTempRect, widthSpec, heightSpec);
}
该方法计算了RecyclerView当前所有Child View的布局范围mRecyclerView.mTempRect,最后调用了public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec),并将得出的布局范围mRecyclerView.mTempRect、RecyclerView的测量参数widthSpec、heightSpec作为参数传入,以此来决定RecyclerView最终宽高值。
最终解决方法
因此,我们只需要重写LayoutManager的public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec)方法即可为RecyclerView设置最大宽高。
` @Override
public void setMeasuredDimension(Rect childrenBounds, int wSpec, int hSpec) {
super.setMeasuredDimension(childrenBounds, wSpec, View.MeasureSpec.makeMeasureSpec(DeviceUtil.dp2px(mContext,246), AT_MOST));
}`
属性的标签实现
标签的实现用的是flowlayout,用法很简单,这里就不在描述了。
至此,如图的效果就实现了,还有不懂的可看demo代码。
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