本文主要是介绍PullBezierZoomView 一个具有贝塞尔曲线下拉效果的自定义view，希望对大家解决编程问题提供一定的参考价值，需要的开发者们随着小编来一起学习吧！
该控件效果基于PullZoomView源码改动的而来,感谢Frank-Zhu的开源代码.该控件具有下拉放大背景图和贝塞尔曲线的效果.
github:https://github.com/X-FAN/PullBezierZoomView 欢迎star
我主要写了一个自定义的贝塞尔曲线的效果的控件并整合到了Frank-Zhu的项目中的一个子项中.
这里面有个小数学知识的求解,因为效果要贝赛尔曲线的曲线顶点要恰好在控件底部边界的中点.所以我们是知道ABC三点,去求贝塞尔曲线的控制点.具体求解过程就不分析了,大家google二阶贝塞尔曲线的公式,很容易就可以推算出来.
源码如下:
public class BezierView extends View {private int mWidth = 500;private int mHeight = 500;private float mMaxHeight = Integer.MAX_VALUE;private float mY = 0;private Paint mPaint;private Path mPath;public BezierView(Context context) {this(context, null);}public BezierView(Context context, AttributeSet attrs) {this(context, attrs, 0);}public BezierView(Context context, AttributeSet attrs, int defStyleAttr) {super(context, attrs, defStyleAttr);mPath = new Path();mPaint = new Paint();mPaint.setAntiAlias(true);mPaint.setColor(Color.WHITE);}@Overrideprotected void onMeasure(int widthMeasureSpec, int 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 if (widthMode == MeasureSpec.AT_MOST) {width = Math.min(mWidth, widthSize);} else {width = mWidth;}if (heightMode == MeasureSpec.EXACTLY) {height = heightSize;} else if (heightMode == MeasureSpec.AT_MOST) {height = Math.min(mHeight, heightSize);} else {height = mHeight;}setMeasuredDimension(width, height);}@Overrideprotected void onSizeChanged(int w, int h, int oldw, int oldh) {super.onSizeChanged(w, h, oldw, oldh);mWidth = w;mHeight = h;}@Overrideprotected void onDraw(Canvas canvas) {super.onDraw(canvas);mPath.reset();//绘制的主要逻辑代码mPath.moveTo(0, mHeight - mY);mPath.quadTo(mWidth / 2, mHeight + mY, mWidth, mHeight - mY);mPath.lineTo(mWidth, mHeight);mPath.lineTo(0, mHeight);mPath.close();canvas.drawPath(mPath, mPaint);}public void setArcHeight(float height) {if (Math.abs(height) < mMaxHeight) {mY = height;invalidate();}}public float getArcHeight() {return mY;}public void setColor(int color) {mPaint.setColor(color);}public void setMaxHeight(float height) {mMaxHeight = height;}
这里提下Frank-Zhu的项目中放大缩小功能的实现是相当的聪明,看了源码发现他是利用ImagView中的scaleType=”centerCrop”属性,只要改变控件的高度,就具有了放大缩小的效果.不用自己写额外的代码,确实很方便.
效果图:
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