RecyclerView调用smoothScrollToPosition() 控制滑动速度

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.     *      * To support smooth scrolling, you must override     * {@link LayoutManager#smoothScrollToPosition(RecyclerView, State, int)} and create a     * {@link SmoothScroller}.     *      * {@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;    }}

转：RecyclerView调用smoothScrollToPosition() 控制滑动速度

自定义LayoutManager

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