无意间看到个需求，要求列表页的第一行放大
效果图：
主要方法是继承RecyclerView重写onScrollStateChanged和onScrolled方法
前者是确定滑动后第一个item可以完全显示，后者是在滑动时进行item改变
主要方法如下
@Override
public void onScrollStateChanged(int state) {
(state);
if(state == 0){
postion = ();
view = (postion);
top = ();
if(viewHeight == 0){
viewHeight = ();
}
if(top == 0){//不用偏移
return;
}
else if(-top < viewHeight/2){ //遮挡小于1/2
offset = top;
}
else {
offset = viewHeight+top;
view = (postion+1);
(1.5f);
}
fsfsf = true;
smoothScrollBy(0, offset);
}
}
@Override
public void onScrolled(int dx, int dy) {
(dx, dy);
offsetY+=dy;
firstc = (); //第一个完整可见item
lastc = ();//最后一个完整可见item
first = ();//第一个可见item
last = ();//最后一个可见item
firstview = (firstc);
one = (first);
two = (first +1);//第二可见item --- 用来防止滑动过快item不规格变化
three = (first + 2);//第三可见item --- 用来防止滑动过快item不规格变化
lastv = (last);
if (viewHeight == 0){
flagfirst = first;
flagend = lastc;
viewHeight = ();
lastview = (lastc);
}
if (flagfirst == first -1) {
flag = true;
lastview = (lastc);
}else if (flagfirst == first +1) {
flag = false;
lastview = (lastc);
}
offseta = ();
float sx = 1f+(float) offseta/viewHeight/2;
if(offsetY == 0){
(1.5f);
}else
(sx);
//因为最后一个不是可见item不是完全可见，所以需要减去最后一个完全可见与height的距离
if (distance ==0)
distance =getHeight()-();
offseta = getHeight()-()- distance;
if (dy!=0) {
if (!flag)
offseta = getHeight() - () + (viewHeight - distance) + 20;//20对应ItemDecoration的bottom
}
if (offseta<0)
offseta = 0;
sx = 1f+(float) offseta/viewHeight/2;
(sx);
(1f);
(1f);
flagfirst = first;
if (firstc == first) {//发生偏移时强制变换
(1.5f);
(1f);
}
}
因为抛掷可能会造成有些item变换错乱，所以设置成了不可抛掷
//抛掷速度
@Override
public boolean fling(int velocityX, int velocityY) {
velocityY = 0;//不可抛掷
return (velocityX, velocityY);
}