参数

• Wate Level(水位)

波浪静止时水面距离底部的高度

• Amplitude(振幅)

波浪垂直振动时偏离水面的最大距离

• Wave Length(波长)

一个完整的波浪的水平长度

• Wave Shift(偏移)

波浪相对于初始位置的水平偏移

实现方法

• 绘制一个波形图，填充到View里，移动波形图

  /**
     * Create the shader with default waves which repeat horizontally, and clamp vertically
     */
    private void createShader() {
        mDefaultAngularFrequency = 2.0f * Math.PI / DEFAULT_WAVE_LENGTH_RATIO / getWidth();
        mDefaultAmplitude = getHeight() * DEFAULT_AMPLITUDE_RATIO;
        mDefaultWaterLevel = getHeight() * DEFAULT_WATER_LEVEL_RATIO;
        mDefaultWaveLength = getWidth();

        Bitmap bitmap = Bitmap.createBitmap(getWidth(), getHeight(), Bitmap.Config.ARGB_8888);
        Canvas canvas = new Canvas(bitmap);

        Paint wavePaint = new Paint();
        wavePaint.setStrokeWidth(1);
        wavePaint.setAntiAlias(true);

        // Draw default waves into the bitmap
        // y=Asin(ωx+φ)+h
        final int endX = getWidth() + 1;
        final int endY = getHeight() + 1;

        float[] waveY = new float[endX];

        wavePaint.setColor(mBehindWaveColor);
        wavePaint.setAlpha(150);
        for (int beginX = 0; beginX < endX; beginX++) {
            double wx = beginX * mDefaultAngularFrequency;
            float beginY = (float) (mDefaultWaterLevel + mDefaultAmplitude * Math.sin(wx));
            canvas.drawLine(beginX, beginY, beginX, endY, wavePaint);

            waveY[beginX] = beginY;
        }

        wavePaint.setColor(mFrontWaveColor);
        wavePaint.setAlpha(255);
        final int wave2Shift = (int) (mDefaultWaveLength / 4);
        for (int beginX = 0; beginX < endX; beginX++) {
            canvas.drawLine(beginX, waveY[(beginX + wave2Shift) % endX], beginX, endY, wavePaint);
        }


        // use the bitamp to create the shader
        mWaveShader = new BitmapShader(bitmap, Shader.TileMode.REPEAT, Shader.TileMode.CLAMP);
        mViewPaint.setShader(mWaveShader);
    }

• 调整Bitmap的大小并填充到WaveView
  有了初始波形，当WaveView的属性改变时，只需要对初始波形进行相应的拉伸/压缩和位移就可以得到用户想要的波形。

动画

 private void initAnimation() {
        List<Animator> animators = new ArrayList<>();

        // horizontal animation.
        // wave waves infinitely.
        ObjectAnimator waveShiftAnim = ObjectAnimator.ofFloat(
                mWaveView, "waveShiftRatio", 0f, 1f);
        waveShiftAnim.setRepeatCount(ValueAnimator.INFINITE);
        waveShiftAnim.setDuration(1000);
        waveShiftAnim.setInterpolator(new LinearInterpolator());
        animators.add(waveShiftAnim);

        // vertical animation.
        // water level increases from 0 to center of WaveView
        ObjectAnimator waterLevelAnim = ObjectAnimator.ofFloat(
                mWaveView, "waterLevelRatio", 0f, 0.3f);
        waterLevelAnim.setDuration(500);
        waterLevelAnim.setInterpolator(new DecelerateInterpolator());
        animators.add(waterLevelAnim);

        // amplitude animation.
        // wave grows big then grows small, repeatedly
        ObjectAnimator amplitudeAnim = ObjectAnimator.ofFloat(
                mWaveView, "amplitudeRatio", 0.0001f, 0.1f);
        amplitudeAnim.setRepeatCount(ValueAnimator.INFINITE);
        amplitudeAnim.setRepeatMode(ValueAnimator.REVERSE);
        amplitudeAnim.setDuration(15000);
        amplitudeAnim.setInterpolator(new LinearInterpolator());
        animators.add(amplitudeAnim);

        mAnimatorSet = new AnimatorSet();
        mAnimatorSet.playTogether(animators);
    }