PorterDuffXfermodeMode.DST_IN

package com.loaderman.customviewdemo.view;

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.PorterDuff;
import android.graphics.PorterDuffXfermode;
import android.graphics.Rect;
import android.util.AttributeSet;
import android.view.View;
import android.view.animation.LinearInterpolator;

import com.loaderman.customviewdemo.R;


public class IrregularWaveView extends View {

    private Paint mPaint;
    private int mItemWaveLength = 0;
    private int dx=0;

    private Bitmap BmpSRC,BmpDST;

    public IrregularWaveView(Context context, AttributeSet attrs) {
        super(context, attrs);
        mPaint = new Paint();

        BmpDST = BitmapFactory.decodeResource(getResources(), R.drawable.wave_bg, null);
        BmpSRC = BitmapFactory.decodeResource(getResources(),R.drawable.circle_shape,null);
        mItemWaveLength = BmpDST.getWidth();

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

    canvas.drawColor(Color.WHITE);

    //先画上圆形
    canvas.drawBitmap(BmpSRC,0,0,mPaint);
    //再画上结果
    int layerId = canvas.saveLayer(0, 0, getWidth(), getHeight(), null, Canvas.ALL_SAVE_FLAG);
    canvas.drawBitmap(BmpDST,new Rect(dx,0,dx+BmpSRC.getWidth(),BmpSRC.getHeight()),new Rect(0,0,BmpSRC.getWidth(),BmpSRC.getHeight()),mPaint);
    mPaint.setXfermode(new PorterDuffXfermode(PorterDuff.Mode.DST_IN));
    canvas.drawBitmap(BmpSRC,0,0,mPaint);
    mPaint.setXfermode(null);
    canvas.restoreToCount(layerId);
}


public void startAnim(){
    ValueAnimator animator = ValueAnimator.ofInt(0,mItemWaveLength);
    animator.setDuration(4000);
    animator.setRepeatCount(ValueAnimator.INFINITE);
    animator.setInterpolator(new LinearInterpolator());
    animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
        public void onAnimationUpdate(ValueAnimator animation) {
            dx = (Integer)animation.getAnimatedValue();
            postInvalidate();
        }
    });
    animator.start();
}
}

  <com.loaderman.customviewdemo.view.IrregularWaveView
      android:layout_width="match_parent"
      android:layout_height="match_parent" />