Canvas实现炫酷动画SearchView

Posted 2022-11-25 花花young

前言

       在Android官方对Canvas描述是：Canvas类容纳所有和Draw（绘制）相关的方法。为了去Draw，你需要具备四个要素，1是Bitmap用来承载像素信息、2是Canvas用来管理Draw相关方法、3是绘制基元（例如，Rect，Path，text，Bitmap）、4是一个画笔（用来描述图像的颜色和风格）

本文之前有关于Paint的文章

绘图不可或缺的画笔Paint-使用篇 

绘图不可或缺的画笔Paint-渲染篇 

绘图不可或缺的画笔Paint-滤镜篇

Part 1、Canvas实现炫酷的搜索

效果~

    

实现此功能很简单，只要动态改变圆弧区域和把手区域即可,这里我们让把手与竖直方向成45度角，如下图所示

1、绘制正常的图形

看代码

    private void drawNormalView(Paint paint, Canvas canvas) 
        centerX = getWidth() / 2;
        centerY = getHeight() / 2;
        circleL = Math.PI * 2 * RADios;

        mRectF.left = centerX - RADIOS;
        mRectF.right = centerX + RADIOS;
        mRectF.top = centerY - RADIOS;
        mRectF.bottom = centerY + RADIOS;
        //设置画笔的样式
        paint.setAntiAlias(true);
        paint.setColor(Color.WHITE);
        paint.setStrokeWidth(5);
        paint.setStyle(Paint.Style.STROKE);
        canvas.drawArc(mRectF, 0, 360, false, paint);

        float startX = (float) (Math.sin(angle) * RADIOS + centerX);
        float startY = (float) (Math.cos(angle) * RADIOS + centerY);
        float endX = (float) (Math.sin(angle) * (RADIOS + LINE) + centerX);
        float endY = (float) (Math.cos(angle) * (RADIOS + LINE) + centerY);
        canvas.drawLine(startX, startY, endX, endY, paint);
    

上面是直观的绘制方式，当然我们也可以使用Canvas的旋转来实现，我们只需要在绘制把手之前的时候将画布旋转45度，然后在save和restore将画布保存并恢复为原始的状态。

    private void drawNormalView(Paint paint, Canvas canvas) 
        cr = getWidth() / 20;
        cx = getWidth() / 2;
        cy = getHeight() / 2;
        radiusL = (float) (Math.PI * cr * 2);
        //绘制的圆形范围
       mRectF.left = cx - cr;
        mRectF.right = cx + cr;
        mRectF.top = cy - cr;
        mRectF.bottom = cy + cr;
        canvas.save();
        //设置画笔
       paint.reset();
        paint.setAntiAlias(true);
        paint.setColor(Color.WHITE);
        paint.setStrokeWidth(5);
        paint.setStyle(Paint.Style.STROKE);
        canvas.rotate(45, cx, cy);
        canvas.drawLine(cx + cr, cy, cx + cr * 2, cy, paint);//绘制把手
        canvas.drawArc(mRectF,0,360,false,paint);
        canvas.restore();
    

tips:

canvas:drawArc() ： startAngle:其实角度，相对于X轴正方向   sweepAngle : 画多少角度的弧度（正值顺时针旋转）   userCenter ： false只有一个纯弧线 true闭合的边

效果~

2、绘制动态时候的效果

这里我们使用一个属性动画来不断更新绘制的进度

        ValueAnimator valueAnimator = ValueAnimator.ofFloat(0, 1);
        valueAnimator.setDuration(800l);
        valueAnimator.setInterpolator(new LinearInterpolator());
        valueAnimator.addUpdateListener(new AnimatorUpdateListener() 
            @Override
            public void onAnimationUpdate(ValueAnimator animation) 
                mpro = (float) animation.getAnimatedValue();
                mySearchView.invalidate();
            
        );

就这样mpro的范围为0~1，根据这个范围来进行绘制即可，这里可以分为2部分：一部分为0~0.5  一部分为0.5~1

（1）0~0.5阶段

        if (mpro < 0.5) //绘制圆和把手
            canvas.drawArc(mRectF, 45, 360 * (mpro * 2 - 1), false, paint);
            float startX = (float) (Math.sin(angle) * RADIOS + centerX);
            float startY = (float) (Math.cos(angle) * RADIOS + centerY);
            float endX = (float) (Math.sin(angle) * (RADIOS + LINE) + centerX);
            float endY = (float) (Math.cos(angle) * (RADIOS + LINE) + centerY);
            canvas.drawLine(startX, startY, endX, endY, paint);
            L = circleL * (360 * mpro * 2) / 360f;

这里记录了一下去掉圆弧的长度，用来对搜索图形平移

（2）0.5~1.0阶段

           float startX = (float) (Math.sin(angle) * (RADIOS + LINE * (mpro * 2 - 1)) + centerX);
            float startY = (float) (Math.cos(angle) * (RADIOS + LINE * (mpro * 2 - 1)) + centerY);
            float endX = (float) (Math.sin(angle) * (RADIOS + LINE) + centerX);
            float endY = (float) (Math.cos(angle) * (RADIOS + LINE) + centerY);
            canvas.drawLine(startX, startY, endX, endY, paint);
            L = L + LINE * (mpro * 2 - 1);

Ok，最后不要忘记绘制底部的线

        float endX = (float) (Math.sin(angle) * (RADIOS + LINE) + centerX);
        float endY = (float) (Math.cos(angle) * (RADIOS + LINE) + centerY);
        float startX = (float) (endX - L);
        float startY = endY;
        canvas.drawLine(startX, startY, endX, endY, paint);

就这样炫酷的搜索搞定了。当然你可以为搜索图形增加平移的效果

        mRectF.left = (float) (getWidth() / 2f - RADIOS + (getWidth() / 3f) * mpro);
        mRectF.right = mRectF.left + 2 * RADIOS;
        mRectF.top = getHeight() / 2f - RADIOS;
        mRectF.bottom = getHeight() / 2f + RADIOS;
        centerX = mRectF.left + RADIOS;
        centerY = mRectF.top + RADIOS;

效果~