How can achieve this custom view wave animation?

Question

I'm trying to achieve this custom wave animation with circle in the middle of the wave.

Below is my custom view. It runs in a different direction and the draw has a line in the middle of the wave that results in a bad UX.

I try to follow some related tutorials but I cannot get the same animation. If there is any library o code sample to follow it could help me a lot.

Thanks.

import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.Rect;
import android.graphics.Region;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.LinearInterpolator;

import com.guille.stressmeterapp.R;

import org.jetbrains.annotations.Nullable;


public class WaveCustomView extends View {

    private int mWidth = 0;
    private int mHeight = 0;
    private Path path;
    private Paint paint;
    private int waveHeight = 300;
    private int waveWidth = 600;



    private int originalY = 750;
    private Region region;
    private int dx = 0;
    private Bitmap mBitmap;


    private int animationDuration = 3000;

    public WaveCustomView(Context context) {
        super(context, null);
        initUi();
    }

    public WaveCustomView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs, 0);
        initUi();
    }

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

    private void initUi() {
        paint = new Paint();
        paint.setAntiAlias(true);
        paint.setColor(Color.parseColor("#000000"));
        paint.setStyle(Paint.Style.STROKE);
        paint.setStrokeWidth(15);
        path = new Path();
        mBitmap = BitmapFactory.decodeResource(getResources(), R.drawable.circle);
    }


    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        int widthMode = MeasureSpec.getMode(widthMeasureSpec);
        int widthSize = MeasureSpec.getSize(widthMeasureSpec);
        int heightMode = MeasureSpec.getMode(heightMeasureSpec);
        int heightSize = MeasureSpec.getSize(heightMeasureSpec);
        int width;
        int height;

        if (widthMode == MeasureSpec.EXACTLY) {
            width = widthSize;
        } else {
            int desired = (int) (getPaddingLeft() + getPaddingRight());
            width = desired;
        }

        if (heightMode == MeasureSpec.EXACTLY) {
            height = heightSize;
        } else {
            int desired = (int) (getPaddingTop() + getPaddingBottom());
            height = desired;
        }
        mWidth = width;
        mHeight = height;
        waveWidth = mWidth / 2;
        setMeasuredDimension(width, height);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        canvas.drawPath(path, paint);
        setDrawData();
        Rect bounds = region.getBounds();
        if (bounds.top < originalY) {
            canvas.drawBitmap(mBitmap,  bounds.right - (mBitmap.getWidth() >> 1), bounds.top - (mBitmap.getHeight() >> 1), paint);
        } else {
            canvas.drawBitmap(mBitmap, bounds.right - (mBitmap.getWidth() >> 1), bounds.bottom - (mBitmap.getHeight() >> 1), paint);
        }
    }

    private void setDrawData() {
        path.reset();
        int halfWaveWidth = waveWidth / 2;
        path.moveTo(-waveWidth + dx, originalY);

        for (int i = -waveWidth; i < mWidth + waveWidth; i = i + waveWidth) {
            path.rQuadTo(halfWaveWidth >> 1, -waveHeight, halfWaveWidth, 0);
            path.rQuadTo(halfWaveWidth >> 1, waveHeight, halfWaveWidth, 0);
        }
        region = new Region();
        Region clip = new Region((int) (mWidth / 2 - 0.1), 0, mWidth / 2, mHeight * 2);
        region.setPath(path, clip);
        path.close();
    }

    public void startAnimate() {
        ValueAnimator animator = ValueAnimator.ofFloat(0, 1);
        animator.setRepeatCount(ValueAnimator.INFINITE);
        animator.setInterpolator(new LinearInterpolator());
        animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
            @Override
            public void onAnimationUpdate(ValueAnimator valueAnimator) {
                float factor = (float) valueAnimator.getAnimatedValue();
                dx = (int) ((waveWidth) * factor);
                invalidate();
            }
        });
        animator.setDuration(animationDuration);
        animator.start();
    }

Answer 1

Your code looks OK. Just remove this line from setDrawData method.

path.close();

This line closes path. It means it connect path begginnig with path end. That's why you see line in the middle of the wave. Here is result without middle line:

If you want to change the direction of animation just change sign of dx variable. Change this:

dx = (int) ((waveWidth) * factor);

To this:

dx = - (int) (waveWidth * factor);

Or instead of this:

path.moveTo(-waveWidth + dx, originalY);

Do this:

path.moveTo(-waveWidth - dx, originalY);

Final result: