android-改造layoutmanager实现弧形滚动和中间放大的效果
时间: 2024-03-23 22:44:09 浏览: 18
实现弧形滚动和中间放大的效果需要自定义LayoutManager。具体步骤如下:
1. 继承LinearLayoutManager,重写calculateExtraLayoutSpace方法,将多余空间分配给中间的item。
```java
public class ArcLayoutManager extends LinearLayoutManager {
private float mShrinkAmount = 0.15f;
private float mShrinkDistance = 0.9f;
private int mVerticalOffset;
private Context mContext;
public ArcLayoutManager(Context context) {
super(context);
mContext = context;
}
@Override
protected int calculateExtraLayoutSpace(RecyclerView.State state, int extraLayoutSpace, int[] extraLayoutSpaceInOther) {
int height = getHeight();
int width = getWidth();
int itemCount = getItemCount();
int extra = (int) (width * (1 - Math.pow(1 - mShrinkAmount, itemCount))) / 2;
return Math.max(extra, extraLayoutSpace);
}
}
```
2. 重写scrollVerticallyBy方法,实现滚动时弧形效果。
```java
@Override
public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
int scrolled = super.scrollVerticallyBy(dy, recycler, state);
mVerticalOffset += scrolled;
float midpoint = getHeight() / 2.f;
float d0 = 0.f;
float d1 = mShrinkDistance * midpoint;
float s0 = 1.f;
float s1 = 1.f - mShrinkAmount;
for (int i = 0; i < getChildCount(); i++) {
View child = getChildAt(i);
float childMidpoint = (getDecoratedBottom(child) + getDecoratedTop(child)) / 2.f;
float d = Math.min(d1, Math.abs(midpoint - childMidpoint));
float scale = s0 + (s1 - s0) * (d - d0) / (d1 - d0);
child.setScaleX(scale);
child.setScaleY(scale);
}
return scrolled;
}
```
3. 在LayoutManager中重写generateDefaultLayoutParams方法,设置item的宽高。
```java
@Override
public RecyclerView.LayoutParams generateDefaultLayoutParams() {
return new RecyclerView.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
}
```
4. 在RecyclerView中设置LayoutManager为自定义的ArcLayoutManager。
```java
recyclerView.setLayoutManager(new ArcLayoutManager(this));
```
5. 最后,在RecyclerView的Adapter中为item设置宽高和布局参数。
```java
@Override
public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
ViewGroup.LayoutParams layoutParams = holder.itemView.getLayoutParams();
layoutParams.width = (int) (mContext.getResources().getDisplayMetrics().widthPixels * 0.7f);
layoutParams.height = (int) (layoutParams.width * 1.2f);
holder.itemView.setLayoutParams(layoutParams);
}
```
这样,就可以实现弧形滚动和中间放大的效果了。