RecycleView横向滑轮轮实现

RecycleView横向滑动，要求实现如下滑轮蓝条可以随着手势跟随RecycleView界面左右滑动，类似滚轴

1.自定义View，单独设置setxoffSet()可实现滚动

package com.wttech.gm.tranmg.view;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.RectF;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.view.ViewTreeObserver;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.RecyclerView;

import com.wttech.gm.tranmg.R;

/**
 * @author LZY
 * @time 2020-04-15.
 */
public class BottomGlideScrollView extends View {
    private Paint mPaint;
    private Path mPath;
    private int mBgColor = 0xffEDEDED;
    private int mScrollCollor = 0xff4090FF;
    private float mScrollWidth = 20;//滚轮宽度
    private float mScrollPostion = 0;//滚轮距离左边间距
    private float inVisableWidth = 0;//RecycleView不可见宽度
    private LinearLayoutManager layoutManager;

    public static final String TAG = "BottomGlideScrollView";

    public BottomGlideScrollView(Context context) {
        this(context, null);
    }

    public BottomGlideScrollView(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

    public BottomGlideScrollView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        if (attrs != null) {
            TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.BottomGlideScrollView);
            mScrollWidth = (int) ta.getDimension(R.styleable.BottomGlideScrollView_scrollWidth, 20);
            ta.recycle();
        }
        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setStrokeCap(Paint.Cap.ROUND);
        mPaint.setStrokeJoin(Paint.Join.ROUND);
        mPaint.setStyle(Paint.Style.FILL);
        mPaint.setStrokeWidth(5);
        mPath = new Path();
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        drawOrginBg(canvas);
        drawScrollBg(canvas);
    }

    private void drawOrginBg(Canvas c) {
        int width = getWidth();
        drawLayout(c, width, mBgColor, 0);
    }

    private void drawScrollBg(Canvas c) {
        drawLayout(c, mScrollWidth, mScrollCollor, mScrollPostion);
    }

    private void drawLayout(Canvas c, float width, int color, float xoffset) {
        mPath.reset();
        mPaint.setColor(color);
        int height = getHeight();
        float radius = height / 2.0f;
        if (xoffset + width > getWidth()) {
            xoffset = (float) getWidth() - width;
        }
        RectF rectLeft = new RectF(xoffset, 0, height + xoffset, height);
        mPath.arcTo(rectLeft, 90, 180, false);
        mPath.moveTo(radius + xoffset, 0);
        mPath.lineTo(width - radius + xoffset, 0);
        mPath.lineTo(width - radius + xoffset, height);
        mPath.lineTo(radius + xoffset, height);
        mPath.close();
        RectF rectRight = new RectF(width - radius * 2 + xoffset, 0, width + xoffset, height);
        mPath.arcTo(rectRight, 270, 180, true);
        c.drawPath(mPath, mPaint);
    }

    /**
     * 设置scroll距离左边间距
     *
     * @param xoffset
     */
    public void setxoffSet(float xoffset) {
        if (xoffset < 0) {
            xoffset = 0;
        }
        if (inVisableWidth > 0) {
            mScrollPostion = (xoffset / inVisableWidth) * (getWidth() - mScrollWidth);
        } else {
            mScrollPostion = 0.0f;
        }
        invalidate();
    }

    public void setPaintWidth(int visableWidth, int totalWidth) {
        inVisableWidth = totalWidth - visableWidth;
        if (inVisableWidth < 0) {
            inVisableWidth = 0;
        }
        float percent = (float) visableWidth / totalWidth;
        if (percent <= 0 || percent > 1) {
            percent = 1;
        }
        mScrollWidth = (getWidth() * percent);
    }

    /**
     * 与RecycleView绑定，获取rv滚动距离
     *
     * @param recyclerView
     * @return
     */
    public int getRvScrollDistance(RecyclerView recyclerView) {
        View firstVisibleItem = recyclerView.getChildAt(0);
        int firstItemPosition = layoutManager.findFirstVisibleItemPosition();
        int itemWidth = firstVisibleItem.getWidth();
        int firstItemRight = layoutManager.getDecoratedRight(firstVisibleItem);
        return (firstItemPosition + 1) * itemWidth - firstItemRight;
    }


    /**
     * 与RecycleView绑定，获取rv全部宽度
     * 并不是严格意义宽度
     *
     * @param recyclerView
     * @return
     */
    public int getRvTotalWidth(RecyclerView recyclerView) {
        int width = 0;
        View firstVisibleItem = recyclerView.getChildAt(0);
        if (firstVisibleItem == null) {
            return width;
        }
        int decoratedWidth = layoutManager.getDecoratedMeasuredWidth(firstVisibleItem);
        Log.i(TAG, "decoratedWidth:" + decoratedWidth + "，firstVisibleItem:" + firstVisibleItem.getWidth());
        int size = layoutManager.getItemCount();
        if (size > 0) {
            width = decoratedWidth * (size - 1) + firstVisibleItem.getWidth();
        }
        return width;
    }

    /**
     * 绑定联动Recycleview
     */
    public void bindRecycleView(RecyclerView recyclerView) {
        layoutManager = (LinearLayoutManager) recyclerView.getLayoutManager();
        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {

            @Override
            public void onScrolled(@NonNull RecyclerView recyclerView, int dx, int dy) {
                super.onScrolled(recyclerView, dx, dy);
                float scrollY = getRvScrollDistance(recyclerView);
                setPaintWidth(recyclerView.getWidth(), getRvTotalWidth(recyclerView));
                setxoffSet(scrollY);
                Log.i(TAG, "scrollY:" + scrollY + "---width:" + recyclerView.getWidth());
            }
        });
        //监听数据改变layout，更新显示条宽度
       recyclerView.getViewTreeObserver().addOnGlobalLayoutListener(new ViewTreeObserver.OnGlobalLayoutListener() {
           @Override
           public void onGlobalLayout() {
               setPaintWidth(recyclerView.getWidth(), getRvTotalWidth(recyclerView));
           }
       });
    }
}

attrs.xml

    <declare-styleable name="BottomGlideScrollView">
        <attr name="scrollWidth" format="dimension|reference"/>
    </declare-styleable>

2.布局文件

 <com.custom.BottomGlideScrollView
                android:id="@+id/bottomGlideScrollView"               
                android:layout_width="@dimen/dp40"
                android:layout_height="@dimen/dp4"
                app:scrollWidth="@dimen/dp15"
                />

3.Activity

  LinearLayoutManager linearLayoutManager = new LinearLayoutManager(getContext());
  linearLayoutManager.setOrientation(RecyclerView.HORIZONTAL);
  recycleview.setLayoutManager(linearLayoutManager);
  //将RecycleView与控件绑定
  bottomGlideScrollView.bindRecycleView(recycleview);