利用贝塞尔曲线自定义View实现水波纹曲线

首先自定义属性

其次自定义View

package com.*********;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.os.Build;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.Nullable;
import androidx.annotation.RequiresApi;

import com.**********.R;

public class WaveView extends View {

    private static final String TAG = "WaveView";
    private int width = 0;
    private int height = 0;
    private Path shapePath;
    private int step = 20;
    private Paint fillPaint;

    private double omega;
    private double phi;
    private double delta = -2;//每次位移角度，大于0向左，小于0 向右
    private boolean fillTop = true;
    private int waveColor;

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

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

    public WaveView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.WaveView);
        initParams(context, typedArray);
        typedArray.recycle();
    }

    @RequiresApi(api = Build.VERSION_CODES.LOLLIPOP)
    public WaveView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.WaveView);
        initParams(context, typedArray);
        typedArray.recycle();
    }


    private void initParams(Context context, TypedArray typedArray) {
        waveColor = typedArray.getColor(R.styleable.WaveView_color, Color.parseColor("#3958AA"));
        fillTop = typedArray.getInt(R.styleable.WaveView_fill_mode, 1) == 1;// 默认绘制上层
        delta = typedArray.getFloat(R.styleable.WaveView_speed, -2); //默认向右移动
        omega = typedArray.getFloat(R.styleable.WaveView_omega, 3 * 1.0f / 4);// 角频率
        phi = typedArray.getFloat(R.styleable.WaveView_phi, 0) * Math.PI / 180 + Math.PI / 2 * -1;// 初始相位角
        fillPaint = new Paint(Paint.ANTI_ALIAS_FLAG);
        fillPaint.setStrokeWidth(1);
        fillPaint.setStyle(Paint.Style.FILL);
        fillPaint.setColor(waveColor);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        shapePath = new Path();
        if (fillTop)
            shapePath.moveTo(0, 0);
        else
            shapePath.moveTo(0, height + 1);
        for (int x = 0; x <= width; x += step) {
            double angle = x * 1.0f / width * 2 * Math.PI;// 弧度
            double y = height / 2 * Math.sin(angle * omega + phi);
            shapePath.lineTo(x, (float) y + height / 2);
        }

        if (fillTop) {
            shapePath.lineTo(width, 0);
        } else {
            shapePath.lineTo(width, height + 1);
        }
        canvas.drawPath(shapePath, fillPaint);

        postInvalidateDelayed(25); // 每秒刷新40次
        addPhi();
    }

    /**
     * 增加相位角
     */
    private void addPhi() {
        phi += delta * Math.PI / 180;

        if (phi > Math.PI * 2)
            phi -= Math.PI * 2;
        else if (phi < Math.PI * -2)
            phi += Math.PI * 2;
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        /**
         * 组件测量
         * 布局里指定的size使用布局的size
         * 属性里指定的size使用属性的size
         * 都没有指定，使用默认size
         */
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = 0;
        if (widthMode == MeasureSpec.EXACTLY) {
            widthSize = MeasureSpec.getSize(widthMeasureSpec);
            width = widthSize;
        } else if (widthMode == MeasureSpec.AT_MOST) {
            widthSize = width;
        }
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = 0;
        if (heightMode == MeasureSpec.EXACTLY) {
            heightSize = MeasureSpec.getSize(heightMeasureSpec);
            height = heightSize;
        } else if (heightMode == MeasureSpec.AT_MOST) {
            heightSize = height;
        }
        setMeasuredDimension(widthSize, heightSize);

    }
}

使用时：