RecyclerView 滑动 到指定的Item 有两个 常用的方法 ScrollToPosition（int position）smoothScrollToPosition(int position)
/**
* Starts a smooth scroll to an adapter position.
* <p>
* To support smooth scrolling, you must override
* {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} and create a
* {@link SmoothScroller}.
* <p>
* {@link LayoutManager} is responsible for creating the actual scroll action. If you want to
* provide a custom smooth scroll logic, override
* {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} in your
* LayoutManager.
*
* @param position The adapter position to scroll to
* @see LayoutManager#smoothScrollToPosition(RecyclerView, State, int)
* 平滑滑动
*/
public void smoothScrollToPosition(int position) {
if (mLayoutFrozen) {
return;
}
if (mLayout == null) {
Log.e(TAG, "Cannot smooth scroll without a LayoutManager set. "
+ "Call setLayoutManager with a non-null argument.");
return;
}
//
mLayout.smoothScrollToPosition(this, mState, position); //调用LayoutManager设置滑动
}
/**
* Convenience method to scroll to a certain position.
*
* RecyclerView does not implement scrolling logic, rather forwards the call to
* {@link android.support.v7.widget.RecyclerView.LayoutManager#scrollToPosition(int)}
* @param position Scroll to this adapter position
* @see android.support.v7.widget.RecyclerView.LayoutManager#scrollToPosition(int)
* 滑动方法 没有平滑视觉
*/
public void scrollToPosition(int position) {
if (mLayoutFrozen) {
return;
}
stopScroll();
if (mLayout == null) {
Log.e(TAG, "Cannot scroll to position a LayoutManager set. "
+ "Call setLayoutManager with a non-null argument.");
return;
}
mLayout.scrollToPosition(position); //调用LayoutManager设置滑动
awakenScrollBars();
}
自定义LayoutManager
接下来我们可以自定一个LayoutManager，然后复写LayoutManager中的smoothScrollToPosition(this, mState, position) 方法，来达到控制滑动速度的目的。以LinearLayoutManager为例子，代码如下：
/**
* 控制滑动速度的LinearLayoutManager
*/
public class ScrollSpeedLinearLayoutManger extends LinearLayoutManager {
private float MILLISECONDS_PER_INCH = 0.03f;
private Context contxt;
public ScrollSpeedLinearLayoutManger(Context context) {
super(context);
this.contxt = context;
}
@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
LinearSmoothScroller linearSmoothScroller =
new LinearSmoothScroller(recyclerView.getContext()) {
@Override
public PointF computeScrollVectorForPosition(int targetPosition) {
return ScrollSpeedLinearLayoutManger.this
.computeScrollVectorForPosition(targetPosition);
}
//This returns the milliseconds it takes to
//scroll one pixel.
@Override
protected float calculateSpeedPerPixel
(DisplayMetrics displayMetrics) {
return MILLISECONDS_PER_INCH / displayMetrics.density;
//返回滑动一个pixel需要多少毫秒
}
};
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}
public void setSpeedSlow() {
//自己在这里用density去乘，希望不同分辨率设备上滑动速度相同
//0.3f是自己估摸的一个值，可以根据不同需求自己修改
MILLISECONDS_PER_INCH = contxt.getResources().getDisplayMetrics().density * 0.3f;
}
public void setSpeedFast() {
MILLISECONDS_PER_INCH = contxt.getResources().getDisplayMetrics().density * 0.03f;
}
}