Android开发RecyclerView实现折线图效果

package com.example.recyclelinechart.test;

import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.Nullable;


public class LineView extends View {

    private int maxValue;//最大值
    private int minValue;//最小值
    private int currentValue;//当前值
    private int lastValue;//上一个值
    private int nextValue;//下一个值
    private Paint mPaint;
    private int viewHeight;//控件高度
    private int viewWidth;//控件宽度
    private int distance;//文字高度
    private int pointX;//所有点的x坐标
    private int pointY;//当前点的Y

    private boolean drawLeftLine = true;//是否画左边的线
    private boolean drawRightLine = true;//是否画右边的线

    private float scale;//每一份占多少像素


    public LineView(Context context) {
        super(context);
        init();
    }

    public LineView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public LineView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    public void setCurrentValue(int currentValue) {
        this.currentValue = currentValue;
        invalidate();
    }

    public void setMaxValue(int maxValue) {
        this.maxValue = maxValue;
    }

    public void setMinValue(int minValue) {
        this.minValue = minValue;
    }

    private void init() {

        mPaint = new Paint();
        mPaint.setAntiAlias(true);
        mPaint.setStyle(Paint.Style.FILL);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        initValues();
    }

    private void initValues() {

        //计算文字高度
        mPaint.setTextSize(40);
        Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
        distance = (int) (fontMetrics.descent   Math.abs(fontMetrics.ascent));

        viewHeight = getMeasuredHeight();
        viewWidth = getMeasuredWidth();
        //lineView的x轴的中心
        pointX = viewWidth / 2;
        //(viewHeight - 2 * distance  上下各留出文字的高度，防止显示不全
        scale = (viewHeight - 2 * distance) / (maxValue - minValue);
    }


    @Override
    public void draw(Canvas canvas) {
        super.draw(canvas);
        pointY = (int) (scale * (maxValue - currentValue)   distance);

        drawGraph(canvas);
        drawPoint(canvas);
        drawValue(canvas);
    }

    /**
     * 画数字
     *
     * @param canvas
     */
    private void drawValue(Canvas canvas) {

        mPaint.setTextSize(40);
        mPaint.setColor(Color.parseColor("#ff333333"));
        mPaint.setTextAlign(Paint.Align.CENTER);
        Paint.FontMetrics fontMetrics = mPaint.getFontMetrics();
        //取字体高度的三分之一
        canvas.drawText(currentValue   "", viewWidth / 2, pointY - (fontMetrics.descent   Math.abs(fontMetrics.ascent)) / 3, mPaint);
    }

    public void setlastValue(int lastValue) {
        this.lastValue = lastValue;
    }

    public void setNextValue(int nextValue) {
        this.nextValue = nextValue;
    }

    /**
     * 画折线
     *
     * @param canvas
     */
    private void drawGraph(Canvas canvas) {

        mPaint.setColor(Color.BLUE);
        mPaint.setStrokeWidth(8);

        if (drawLeftLine) {
            float middleValue = (currentValue   lastValue) / 2f;
            float middleY = (scale * (maxValue - middleValue)   distance);
            //ax b = y   二元一次方程，向左多画一点计算y值
            float a = (middleY - pointY) * 1f / (0 - pointX);
            float b = (0 * pointY - pointX * middleY) * 1f / (0 - pointX);
            middleY = a * (0 - 10)   b;

            canvas.drawLine(0 - 10, middleY, pointX, pointY, mPaint);
        }
        if (drawRightLine) {
            float middleValue = (currentValue   nextValue) / 2f;
            float middleY = scale * (maxValue - middleValue)   distance;

            //向右多画一点，机制同上
            float a = (middleY - pointY) * 1f / (viewWidth - pointX);
            float b = (pointX * middleY - viewWidth * pointY) * 1f / (pointX - viewWidth);
            middleY = a * (viewWidth   10)   b;

            canvas.drawLine(pointX, pointY, viewWidth   10, middleY, mPaint);
        }
    }

    /**
     * 画数字下面的小圆圈
     *
     * @param canvas
     */
    private void drawPoint(Canvas canvas) {
        mPaint.setColor(Color.RED);
        mPaint.setPathEffect(null);

        mPaint.setStrokeWidth(10);
        mPaint.setStyle(Paint.Style.FILL);
        canvas.drawCircle(pointX, pointY, 10, mPaint);
    }

    public void setDrawLeftLine(boolean drawLeftLine) {
        this.drawLeftLine = drawLeftLine;
    }

    public void setDrawRightLine(boolean drawRightLine) {
        this.drawRightLine = drawRightLine;
    }
}

public class MyAdapter extends RecyclerView.Adapter<MyAdapter.ViewHolder> {


    private int minValue;
    private int maxValue;
    private List<Integer> data;


    public MyAdapter(int minValue, int maxValue, List<Integer> data) {

        this.minValue = minValue;
        this.maxValue = maxValue;
        this.data = data;
    }

    @Override
    public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {

        View layout = LayoutInflater.from(parent.getContext()).inflate(R.layout.test_line, parent, false);
        return new ViewHolder(layout);
    }

    @Override
    public void onBindViewHolder(ViewHolder holder, int position) {
        if (position == 0) {
            holder.lineView.setDrawLeftLine(false);
        } else {
            holder.lineView.setDrawLeftLine(true);
            holder.lineView.setlastValue((data.get(position - 1)));
        }
        holder.lineView.setMaxValue(maxValue);
        holder.lineView.setMinValue(minValue);
        holder.lineView.setCurrentValue((data.get(position)));


        if (position == data.size() - 1) {
            holder.lineView.setDrawRightLine(false);
        } else {
            holder.lineView.setDrawRightLine(true);
            holder.lineView.setNextValue((data.get(position   1)));
        }
    }

    @Override
    public int getItemCount() {
        return data.size();
    }

    class ViewHolder extends RecyclerView.ViewHolder {
        LineView lineView;

        public ViewHolder(View itemView) {
            super(itemView);
            this.lineView = itemView.findViewById(R.id.item);
        }
    }
}

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:orientation="vertical">


    <TextView
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_gravity="center_horizontal"
        android:layout_marginTop="20dp"
        android:layout_marginBottom="5dp"
        android:text="文字" />

    <com.example.recyclelinechart.test.LineView
        android:id="@ id/item"
        android:layout_width="100dp"
        android:layout_height="100dp" />

    <ImageView
        android:layout_width="20dp"
        android:layout_height="20dp"
        android:layout_gravity="center_horizontal"
        android:layout_marginBottom="20dp"
        android:src="@mipmap/ic_launcher" />

</LinearLayout>

MyAdapter myAdapter = new MyAdapter(2, 30, integers);
        recyclerView.setLayoutManager(new LinearLayoutManager(this, RecyclerView.HORIZONTAL, false));
        recyclerView.setAdapter(myAdapter);