Android动画之小球拟合动画实例
实现效果：
动画组成:
1.通过三阶贝塞尔曲线来拟合圆,拟合系数的由来,以及怎么选控制点.
2.利用画布canvas.translate,以及scale,rotate的方法,来渐变绘制的过程.
3.熟悉拟合过程.
4.不熟悉的话,先绘制辅助点的移动路线,对理解两个圆的分裂的拟合过程有好处.
package com.example.administrator.animationworkdemo.views;
import android.animation.ValueAnimator;
import android.content.Context;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.graphics.Path;
import android.graphics.PathMeasure;
import android.util.AttributeSet;
import android.view.View;
import java.util.concurrent.CyclicBarrier;
/**
* 这个例子中，大家可以发现作者的拟合做的并不是很好，连接的地方比较生硬，大家可以思考下如何改善
* 贝塞尔曲线绘制比较复杂，大家在学习过程中，可以仿照示例中的，将辅助点和线绘制出来，这样会看的更清楚一点
*/
public class BallShapeChangeView extends View {
// 使用贝塞尔曲线来拟合圆的magic number
//C 是三阶贝塞尔曲线拟合 圆的 误差最小 获得控制点的参数.
private static final float C = 0.551915024494f;
private Paint mPaint;
private int mRadiusBig = 120,mRadiusSmall = (int) (mRadiusBig / 2f),mWidth,mHeight,mMimWidth = (int) (mRadiusSmall * 2 * 3)/*fill view mim width*/;
private float mFraction = 0,mFractionDegree = 0,/*degree*/
mLength,mDistanceBezier;
private Path mPathCircle,mPathBezier;
private ValueAnimator mValueAnimator;
private float[] mPointData = new float[8];// 4个数据点 顺时针排序，从左边开始
private float[] mPointCtrl = new float[16];// 8个控制点
private float[] mPos = new float[2];
private PathMeasure mPathMeasure;
private Path mPathBezier2;
public BallShapeChangeView(Context context,AttributeSet attrs) {
super(context,attrs);
mPaint = new Paint();
mPaint.setStyle(Paint.Style.FILL);
mPaint.setColor(0xFF7C191E);
mPaint.setAntiAlias(true);
mPathCircle = new Path();
mPathBezier = new Path();
mPathBezier2 = new Path();
mPathMeasure = new PathMeasure();
mValueAnimator = ValueAnimator.ofFloat(0,1,0);
mValueAnimator.setDuration(3000);
mValueAnimator.setRepeatCount(Integer.MAX_VALUE);
mValueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
mFraction = (float) animation.getAnimatedValue();
mFractionDegree = animation.getAnimatedFraction();
invalidate();
}
});
}
@Override
protected void onMeasure(int widthMeasureSpec,int heightMeasureSpec) {
// 为了能够更好的控制绘制的大小和位置，当然，初学者写死也是可以的
super.onMeasure(widthMeasureSpec,heightMeasureSpec);
mWidth = MeasureSpec.getSize(widthMeasureSpec);
mHeight = MeasureSpec.getSize(heightMeasureSpec);
int widthMode = MeasureSpec.getMode(widthMeasureSpec);
int heightMode = MeasureSpec.getMode(heightMeasureSpec);
if (widthMode != MeasureSpec.AT_MOST && heightMode != MeasureSpec.AT_MOST) {
if (mWidth < mMimWidth)
mWidth = mMimWidth;
if (mHeight < mMimWidth)
mHeight = mMimWidth;
} else if (widthMeasureSpec != MeasureSpec.AT_MOST) {
if (mWidth < mMimWidth)
mWidth = mMimWidth;
} else if (heightMeasureSpec != MeasureSpec.AT_MOST) {
if (mHeight < mMimWidth)
mHeight = mMimWidth;
}
setMeasuredDimension(mWidth,mHeight);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
// 通过mFraction来控制绘图的过程，这是常用的一种方式
canvas.translate(mWidth / 2,mHeight / 2);
canvas.scale(1,-1);
canvas.rotate(-360 * mFractionDegree);
setDoubleCirClePath();
canvas.drawPath(mPathCircle,mPaint);
if (mFraction < (1 / 3f)) {// 缩小大圆
setCirclePath();
canvas.drawPath(mPathCircle,mPaint);
} else if (mFraction < 3 / 4f) {// 画贝塞尔曲线
setBezierPath2();
canvas.drawPath(mPathBezier,mPaint);
canvas.drawPath(mPathBezier2,mPaint);
} else {// 画分离
//setLastBezierPath();
//canvas.drawPath(mPathBezier,mPaint);
}
}
private void setDoubleCirClePath() {
mPathCircle.reset();
if (mFraction < (1 / 3f)) {
mPathCircle.addCircle(-mRadiusSmall / 2f * mFraction * 3,mRadiusSmall,Path.Direction.CW);
mPathCircle.addCircle(mRadiusSmall / 2f * mFraction * 3,Path.Direction.CW);
} else {
float distance = (mFraction - 1 / 3f) / (2 / 3f) * (mRadiusSmall * 2 + mRadiusSmall / 2f);
mPathCircle.addCircle(-mRadiusSmall / 2f - distance,Path.Direction.CW);
mPathCircle.addCircle(mRadiusSmall / 2f + distance,Path.Direction.CW);
}
}
// mFraction 0 ~ 1/3
private void setCirclePath() {
mPointData[0] = -mRadiusBig + mRadiusSmall / 2f * mFraction * 3f;
mPointData[1] = 0;
mPointData[2] = 0;
mPointData[3] = mRadiusBig - mRadiusBig / 2f * mFraction * 3f;//0到1 的三分之一 用来给大圆做效果;
mPointData[4] = mRadiusBig - mRadiusSmall / 2f * mFraction * 3f;
mPointData[5] = 0;
mPointData[6] = mPointData[2];
mPointData[7] = -mPointData[3];
mPointCtrl[0] = mPointData[0];// x轴一样
mPointCtrl[1] = mRadiusBig * C;// y轴向下的
mPointCtrl[2] = mPointData[2] - mRadiusBig * C;
mPointCtrl[3] = mPointData[3];// y轴一样
mPointCtrl[4] = mPointData[2] + mRadiusBig * C;
mPointCtrl[5] = mPointData[3];
mPointCtrl[6] = mPointData[4];
mPointCtrl[7] = mPointCtrl[1];
mPointCtrl[8] = mPointData[4];
mPointCtrl[9] = -mPointCtrl[1];
mPointCtrl[10] = mPointCtrl[4];
mPointCtrl[11] = mPointData[7];
mPointCtrl[12] = mPointCtrl[2];
mPointCtrl[13] = mPointData[7];
mPointCtrl[14] = mPointData[0];
mPointCtrl[15] = -mPointCtrl[1];
mPathCircle.reset();
mPathCircle.moveTo(mPointData[0],mPointData[1]);
mPathCircle.cubicTo(mPointCtrl[0],mPointCtrl[1],mPointCtrl[2],mPointCtrl[3],mPointData[2],mPointData[3]);
mPathCircle.cubicTo(mPointCtrl[4],mPointCtrl[5],mPointCtrl[6],mPointCtrl[7],mPointData[4],mPointData[5]);
mPathCircle.cubicTo(mPointCtrl[8],mPointCtrl[9],mPointCtrl[10],mPointCtrl[11],mPointData[6],mPointData[7]);
mPathCircle.cubicTo(mPointCtrl[12],mPointCtrl[13],mPointCtrl[14],mPointCtrl[15],mPointData[0],mPointData[1]);
}
// mFraction 1/3 ~ 3/4
private void setBezierPath2() {
mPointData[0] = -mRadiusSmall / 2 - (mFraction - 1 / 3f) * mRadiusBig * 2f;
if (mFraction < 2 / 3f) {
mPointData[1] = -mRadiusSmall;
} else {
mPointData[1] = -mRadiusSmall + (mFraction - 2 / 3f) * 3 * mRadiusSmall;
}
if (mFraction < 3 / 4f) {
mPointData[2] = 0;
} else {
//当分裂超过一定程度让结束点的位置变远
mPointData[2] = (mFraction - 3 / 4f) * 16 * mPointData[0];
}
//当动画执行进度大于2/3时,此时该点接近于0
mPointData[3] = -mRadiusBig + mFraction * mRadiusBig * 1.5f < -0.01f * mRadiusBig ? -mRadiusBig + mFraction * mRadiusBig * 1.5f : 0.01f * -mRadiusBig;
mPointData[4] = mPointData[2];
mPointData[5] = -mPointData[3];
mPointData[6] = mPointData[0];
mPointData[7] = -mPointData[1];
mPointCtrl[0] = mPointData[0] + mRadiusSmall;
mPointCtrl[1] = mPointData[3];
mPointCtrl[2] = mPointData[0] + mRadiusSmall;
mPointCtrl[3] = -mPointData[3];
mPathBezier.reset();
mPathBezier.moveTo(mPointData[0],mPointData[1]);
mPathBezier.quadTo(mPointCtrl[0],mPointData[3]);
mPathBezier.lineTo(mPointData[4],mPointData[5]);
mPathBezier.quadTo(mPointCtrl[2],mPointData[7]);
mPathBezier2.reset();
mPathBezier2.moveTo(-mPointData[0],mPointData[1]);
mPathBezier2.quadTo(-mPointCtrl[0],-mPointData[2],mPointData[3]);
mPathBezier2.lineTo(-mPointData[4],mPointData[5]);
mPathBezier2.quadTo(-mPointCtrl[2],-mPointData[6],mPointData[7]);
}
// mFraction 1/3 ~ 3/4
private void setBezierPath() {
mPathBezier.reset();
float distance = (2 * mRadiusSmall + mRadiusSmall / 2f) * mFraction;
//float topY = mRadiusSmall * (1 - 0.6f * mFraction);
float topY = mRadiusSmall - mRadiusSmall * (mFraction - 1 / 3f);
float distanceBezier = topY - distance * C * (0.5f + 0.5f * mFraction);
if (mDistanceBezier != 0 && distanceBezier < (mDistanceBezier)) {
distanceBezier = mDistanceBezier;
}
mPathBezier.moveTo(-distance,topY);
mPathBezier.cubicTo(-distance,distanceBezier,distance,topY);
if (mDistanceBezier == 0) {
mPathMeasure.setPath(mPathBezier,false);
mLength = mPathMeasure.getLength();
mPathMeasure.getPosTan(mLength / 2,mPos,null);
if (mPos[1] <= 8) {
mDistanceBezier = distanceBezier;
mPathBezier.reset();
mPathBezier.moveTo(-distance,topY);
mPathBezier.cubicTo(-distance,mDistanceBezier,topY);
mPathBezier.lineTo(distance,-topY);
mPathBezier.cubicTo(distance,-mDistanceBezier,-distance,-topY);
mPathBezier.close();
return;
}
}
mPathBezier.lineTo(distance,-topY);
mPathBezier.cubicTo(distance,-distanceBezier,-topY);
mPathBezier.close();
}
// mFraction 3/4 ~ 1
private void setLastBezierPath() {
float x = -mRadiusSmall / 2f - (mFraction - 1 / 3f) / (2 / 3f) * (mRadiusSmall * 2 + mRadiusSmall / 2f);
mPathBezier.reset();
mPathBezier.moveTo(x,mRadiusSmall);
mPathBezier.quadTo(x,x + mRadiusSmall + mRadiusSmall * (4 - mFraction * 4),0);
mPathBezier.quadTo(x,x,-mRadiusSmall);
mPathBezier.lineTo(x,mRadiusSmall);
mPathBezier.moveTo(-x,mRadiusSmall);
mPathBezier.quadTo(-x,-x - mRadiusSmall - mRadiusSmall * (4 - mFraction * 4),0);
mPathBezier.quadTo(-x,-x,-mRadiusSmall);
mPathBezier.lineTo(-x,mRadiusSmall);
mPathBezier.close();
}
@Override
protected void onAttachedToWindow() {
super.onAttachedToWindow();
if (!mValueAnimator.isRunning())
mValueAnimator.start();
}
@Override
protected void onDetachedFromWindow() {
super.onDetachedFromWindow();
if (mValueAnimator.isRunning())
mValueAnimator.cancel();
}
}
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