Android 两种方式实现类似水波扩散效果

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两种方式实现类似水波扩散效果，先上图为敬

1. 自定义view实现
2. 动画实现

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自定义view实现

思路分析：通过canvas画圆，每次改变圆半径和透明度，当半径达到一定程度，再次从中心开始绘圆，达到不同层级的效果，通过不断绘制达到view扩散效果

private Paint centerPaint; //中心圆paint
private int radius = 100; //中心圆半径
private Paint spreadPaint; //扩散圆paint
private float centerX;//圆心x
private float centerY;//圆心y
private int distance = 5; //每次圆递增间距
private int maxRadius = 80; //最大圆半径
private int delayMilliseconds = 33;//扩散延迟间隔，越大扩散越慢
private List spreadRadius = new ArrayList<>();//扩散圆层级数，元素为扩散的距离
private List alphas = new ArrayList<>();//对应每层圆的透明度

style文件里自定义属性

初始化

public SpreadView(Context context) {
    this(context, null, 0);
}

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

public SpreadView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
    super(context, attrs, defStyleAttr);
    TypedArray a = context.obtainStyledAttributes(attrs, R.styleable.SpreadView, defStyleAttr, 0);
    radius = a.getInt(R.styleable.SpreadView_spread_radius, radius);
    maxRadius = a.getInt(R.styleable.SpreadView_spread_max_radius, maxRadius);
    int centerColor = a.getColor(R.styleable.SpreadView_spread_center_color, ContextCompat.getColor(context, R.color.colorAccent));
    int spreadColor = a.getColor(R.styleable.SpreadView_spread_spread_color, ContextCompat.getColor(context, R.color.colorAccent));
    distance = a.getInt(R.styleable.SpreadView_spread_distance, distance);
    a.recycle();

    centerPaint = new Paint();
    centerPaint.setColor(centerColor);
    centerPaint.setAntiAlias(true);
    //最开始不透明且扩散距离为0
    alphas.add(255);
    spreadRadius.add(0);
    spreadPaint = new Paint();
    spreadPaint.setAntiAlias(true);
    spreadPaint.setAlpha(255);
    spreadPaint.setColor(spreadColor);
}

确定圆心位置

@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
    super.onSizeChanged(w, h, oldw, oldh);
    //圆心位置
    centerX = w / 2;
    centerY = h / 2;
}

自定义view的绘制

@Override
protected void onDraw(Canvas canvas) {
    super.onDraw(canvas);
    for (int i = 0; i < spreadRadius.size(); i++) {
        int alpha = alphas.get(i);
        spreadPaint.setAlpha(alpha);
        int width = spreadRadius.get(i);
        //绘制扩散的圆
        canvas.drawCircle(centerX, centerY, radius + width, spreadPaint);

        //每次扩散圆半径递增，圆透明度递减
        if (alpha > 0 && width < 300) {
            alpha = alpha - distance > 0 ? alpha - distance : 1;
            alphas.set(i, alpha);
            spreadRadius.set(i, width + distance);
        }
    }
    //当最外层扩散圆半径达到最大半径时添加新扩散圆
    if (spreadRadius.get(spreadRadius.size() - 1) > maxRadius) {
        spreadRadius.add(0);
        alphas.add(255);
    }
    //超过8个扩散圆，删除最先绘制的圆，即最外层的圆
    if (spreadRadius.size() >= 8) {
        alphas.remove(0);
        spreadRadius.remove(0);
    }
    //中间的圆
    canvas.drawCircle(centerX, centerY, radius, centerPaint);
    //TODO 可以在中间圆绘制文字或者图片

    //延迟更新，达到扩散视觉差效果
    postInvalidateDelayed(delayMilliseconds);
}

xml样式

效果图

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中心圆处可以自定义写文字，画图片等等...

动画实现

思路分析：通过动画实现，imageView不停做动画缩放+渐变
最中心的imageView保持不变
中间一层imageView从原始放大到1.4倍，同时从不透明变为半透明
最外层的imageView从1.4倍放大到1.8倍，同时从半透明变为全透明
利用shape画一个圆，作为动画基础视图

布局视图

中间imageView的动画

private void setAnim1() {
    AnimationSet as = new AnimationSet(true);
    //缩放动画，以中心从原始放大到1.4倍
    ScaleAnimation scaleAnimation = new ScaleAnimation(1.0f, 1.4f, 1.0f, 1.4f,
            ScaleAnimation.RELATIVE_TO_SELF, 0.5f,
            ScaleAnimation.RELATIVE_TO_SELF, 0.5f);
    //渐变动画
    AlphaAnimation alphaAnimation = new AlphaAnimation(1.0f, 0.5f);
    scaleAnimation.setDuration(800);
    scaleAnimation.setRepeatCount(Animation.INFINITE);
    alphaAnimation.setRepeatCount(Animation.INFINITE);
    as.setDuration(800);
    as.addAnimation(scaleAnimation);
    as.addAnimation(alphaAnimation);
    iv1.startAnimation(as);
}

最外层imageView的动画

private void setAnim2() {
    AnimationSet as = new AnimationSet(true);
    //缩放动画，以中心从1.4倍放大到1.8倍
    ScaleAnimation scaleAnimation = new ScaleAnimation(1.4f, 1.8f, 1.4f, 1.8f,
            ScaleAnimation.RELATIVE_TO_SELF, 0.5f,
            ScaleAnimation.RELATIVE_TO_SELF, 0.5f);
    //渐变动画
    AlphaAnimation alphaAnimation = new AlphaAnimation(0.5f, 0.1f);
    scaleAnimation.setDuration(800);
    scaleAnimation.setRepeatCount(Animation.INFINITE);
    alphaAnimation.setRepeatCount(Animation.INFINITE);
    as.setDuration(800);
    as.addAnimation(scaleAnimation);
    as.addAnimation(alphaAnimation);
    iv2.startAnimation(as);
}

效果图

image

相比较而言，自定义view的效果更好点，动画实现起来更方便点。

两种方式实现的扩散效果介绍完毕，具体项目里还是要按需变动的。

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