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一步步教你写Slack的Loading动画

时间:2021-01-27 15:54     来源/作者:jeasonwong

项目地址:https://github.com/JeasonWong/SlackLoadingView

老规矩,先上效果。

一步步教你写Slack的Loading动画

图好大。。

说下第一眼看到这个动画后的思路:

+两根平行线,要用到直线方程 y=kx+b
+另外两根平行线,与之前两根平行线的斜率相乘为-1,即k1*k2=-1
+线条做圆周运动就是k值的不断变化
+然后就是简单的线条长度变化

我相信很多人第一眼会和我有类似的思路,但是当我上了个厕所后意识到我想复杂了~

说下上完厕所后的思路:

不要想着线条是斜的,就是一个普通的线段,一个LineTo搞定(startX和stopX一样,仅Y不同)
线条的垂直更容易,直接Canvas翻转(转过后再转回)
整个动画的圆周运动也是Canvas翻转(转过后不转回)
线条的单度变化依然用属性动画(这是必须的。。)
动画开始前就让整个Canvas旋转
这样一来就太容易了。

我把动画分成了四步:

画布旋转及线条变化动画(Canvas Rotate Line Change)
画布旋转动画(Canvas Rotate)
画布旋转圆圈变化动画(Canvas Rotate Circle Change)
线条变化动画(Line Change)

详细说明前先介绍下成员变量和一些初始化

成员变量

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//静止状态
 private final int STATUS_STILL = 0;
 //加载状态
 private final int STATUS_LOADING = 1;
 //线条最大长度
 private final int MAX_LINE_LENGTH = dp2px(getContext(), 120);
 //线条最短长度
 private final int MIN_LINE_LENGTH = dp2px(getContext(), 40);
 //最大间隔时长
 private final int MAX_DURATION = 3000;
 //最小间隔时长
 private final int MIN_DURATION = 500;
 
 private Paint mPaint;
 private int[] mColors = new int[]{0xB07ECBDA, 0xB0E6A92C, 0xB0D6014D, 0xB05ABA94};
 private int mWidth, mHeight;
 //动画间隔时长
 private int mDuration = MIN_DURATION;
 //线条总长度
 private int mEntireLineLength = MIN_LINE_LENGTH;
 //圆半径
 private int mCircleRadius;
 //所有动画
 private List<Animator> mAnimList = new ArrayList<>();
 //Canvas起始旋转角度
 private final int CANVAS_ROTATE_ANGLE = 60;
 //动画当前状态
 private int mStatus = STATUS_STILL;
 //Canvas旋转角度
 private int mCanvasAngle;
 //线条长度
 private float mLineLength;
 //半圆Y轴位置
 private float mCircleY;
 //第几部动画
 private int mStep;

初始化

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private void initView() {
 mPaint = new Paint();
 mPaint.setAntiAlias(true);
 mPaint.setColor(mColors[0]);
}
 
private void initData() {
 mCanvasAngle = CANVAS_ROTATE_ANGLE;
 mLineLength = mEntireLineLength;
 mCircleRadius = mEntireLineLength / 5;
 mPaint.setStrokeWidth(mCircleRadius * 2);
 mStep = 0;
}

一、画布旋转及线条变化动画(Canvas Rotate Line Change)

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/**
 * Animation1
 * 动画1
 * Canvas Rotate Line Change
 * 画布旋转及线条变化动画
 */
private void startCRLCAnim() {
 
 Collection<Animator> animList = new ArrayList<>();
 
 ValueAnimator canvasRotateAnim = ValueAnimator.ofInt(CANVAS_ROTATE_ANGLE + 0, CANVAS_ROTATE_ANGLE + 360);
 canvasRotateAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
   mCanvasAngle = (int) animation.getAnimatedValue();
  }
 });
 
 animList.add(canvasRotateAnim);
 
 ValueAnimator lineWidthAnim = ValueAnimator.ofFloat(mEntireLineLength, -mEntireLineLength);
 lineWidthAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
   mLineLength = (float) animation.getAnimatedValue();
   invalidate();
  }
 });
 
 animList.add(lineWidthAnim);
 
 AnimatorSet animationSet = new AnimatorSet();
 animationSet.setDuration(mDuration);
 animationSet.playTogether(animList);
 animationSet.setInterpolator(new LinearInterpolator());
 animationSet.addListener(new AnimatorListener() {
  @Override
  public void onAnimationEnd(Animator animation) {
   Log.d("@=>", "动画1结束");
   if (mStatus == STATUS_LOADING) {
    mStep++;
    startCRAnim();
   }
  }
 });
 animationSet.start();
 
 mAnimList.add(animationSet);
}

第一步动画涉及到两个动画同时进行,所以使用了AnimatorSet,这个类很强大,可以让N个动画同时进行(playTogether),也可以让N个动画顺序执行(playSequentially)。

说到这里,其实我的四个动画就是顺序进行的,但是每个动画里又有同时进行的动画,为了讲解方便,我是监听了onAnimationEnd来控制动画执行顺序,其实可以直接使用playSequentially。

上方动画就干了两件事:

1、旋转画布,从CANVAS_ROTATE_ANGLE + 0转到CANVAS_ROTATE_ANGLE + 360,CANVAS_ROTATE_ANGLE是画布初始倾斜角度

2、线条长度变化,从mEntireLineLength到-mEntireLineLength。

对应的onDraw方法:

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@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 switch (mStep % 4) {
  case 0:
   for (int i = 0; i < mColors.length; i++) {
    mPaint.setColor(mColors[i]);
    drawCRLC(canvas, mWidth / 2 - mEntireLineLength / 2.2f, mHeight / 2 - mLineLength, mWidth / 2 - mEntireLineLength / 2.2f, mHeight / 2 + mEntireLineLength, mPaint, mCanvasAngle + i * 90);
   }
   break;
  ...
 }
 
}
 
...
 
private void drawCRLC(Canvas canvas, float startX, float startY, float stopX, float stopY, @NonNull Paint paint, int rotate) {
 canvas.rotate(rotate, mWidth / 2, mHeight / 2);
 canvas.drawArc(new RectF(startX - mCircleRadius, startY - mCircleRadius, startX + mCircleRadius, startY + mCircleRadius), 180, 180, true, mPaint);
 canvas.drawLine(startX, startY, stopX, stopY, paint);
 canvas.drawArc(new RectF(stopX - mCircleRadius, stopY - mCircleRadius, stopX + mCircleRadius, stopY + mCircleRadius), 0, 180, true, mPaint);
 canvas.rotate(-rotate, mWidth / 2, mHeight / 2);
}

是不是很机智,drawCRLC做了三件事:

1、画布旋转后又旋转回来

2、画半圆(为什么要画半圆?不画整个圆?这里留个思考题。)

3、画线条

这样动画1就完成了。

二、画布旋转动画(Canvas Rotate)

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/**
 * Animation2
 * 动画2
 * Canvas Rotate
 * 画布旋转动画
 */
private void startCRAnim() {
 ValueAnimator canvasRotateAnim = ValueAnimator.ofInt(mCanvasAngle, mCanvasAngle + 180);
 canvasRotateAnim.setDuration(mDuration / 2);
 canvasRotateAnim.setInterpolator(new LinearInterpolator());
 canvasRotateAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
   mCanvasAngle = (int) animation.getAnimatedValue();
   invalidate();
  }
 });
 canvasRotateAnim.addListener(new AnimatorListener() {
  @Override
  public void onAnimationEnd(Animator animation) {
   Log.d("@=>", "动画2结束");
   if (mStatus == STATUS_LOADING) {
    mStep++;
    startCRCCAnim();
   }
  }
 });
 canvasRotateAnim.start();
 
 mAnimList.add(canvasRotateAnim);
}
 
...
 
@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 switch (mStep % 4) {
  ...
  case 1:
   for (int i = 0; i < mColors.length; i++) {
    mPaint.setColor(mColors[i]);
    drawCR(canvas, mWidth / 2 - mEntireLineLength / 2.2f, mHeight / 2 + mEntireLineLength, mPaint, mCanvasAngle + i * 90);
   }
   break;
  ...
 }
 
}
 
...
 
private void drawCR(Canvas canvas, float x, float y, @NonNull Paint paint, int rotate) {
 canvas.rotate(rotate, mWidth / 2, mHeight / 2);
 canvas.drawCircle(x, y, mCircleRadius, paint);
 canvas.rotate(-rotate, mWidth / 2, mHeight / 2);
}

有了动画1的底子,那这个就太容易了,只是简单的旋转Canvas。

三、画布旋转圆圈变化动画(Canvas Rotate Circle Change)

 

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/**
 * Animation3
 * 动画3
 * Canvas Rotate Circle Change
 * 画布旋转圆圈变化动画
 */
private void startCRCCAnim() {
 Collection<Animator> animList = new ArrayList<>();
 
 ValueAnimator canvasRotateAnim = ValueAnimator.ofInt(mCanvasAngle, mCanvasAngle + 90, mCanvasAngle + 180);
 canvasRotateAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
   mCanvasAngle = (int) animation.getAnimatedValue();
  }
 });
 
 animList.add(canvasRotateAnim);
 
 ValueAnimator circleYAnim = ValueAnimator.ofFloat(mEntireLineLength, mEntireLineLength / 4, mEntireLineLength);
 circleYAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
   mCircleY = (float) animation.getAnimatedValue();
   invalidate();
  }
 });
 
 animList.add(circleYAnim);
 
 AnimatorSet animationSet = new AnimatorSet();
 animationSet.setDuration(mDuration);
 animationSet.playTogether(animList);
 animationSet.setInterpolator(new LinearInterpolator());
 animationSet.addListener(new AnimatorListener() {
  @Override
  public void onAnimationEnd(Animator animation) {
   Log.d("@=>", "动画3结束");
   if (mStatus == STATUS_LOADING) {
    mStep++;
    startLCAnim();
   }
  }
 });
 animationSet.start();
 
 mAnimList.add(animationSet);
}
 
...
 
@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 switch (mStep % 4) {
  ...
  case 2:
   for (int i = 0; i < mColors.length; i++) {
    mPaint.setColor(mColors[i]);
    drawCRCC(canvas, mWidth / 2 - mEntireLineLength / 2.2f, mHeight / 2 + mCircleY, mPaint, mCanvasAngle + i * 90);
   }
   break;
  ...
 }
 
}
 
...
 
private void drawCRCC(Canvas canvas, float x, float y, @NonNull Paint paint, int rotate) {
 canvas.rotate(rotate, mWidth / 2, mHeight / 2);
 canvas.drawCircle(x, y, mCircleRadius, paint);
 canvas.rotate(-rotate, mWidth / 2, mHeight / 2);
}

动画3做了两件事:

1、旋转Canvas

2、变化Circle的Y坐标,达到往里缩的效果

四、线条变化动画(Line Change)

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/**
 * Animation4
 * 动画4
 * Line Change
 * 线条变化动画
 */
private void startLCAnim() {
 ValueAnimator lineWidthAnim = ValueAnimator.ofFloat(mEntireLineLength, -mEntireLineLength);
 lineWidthAnim.setDuration(mDuration);
 lineWidthAnim.setInterpolator(new LinearInterpolator());
 lineWidthAnim.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
  @Override
  public void onAnimationUpdate(ValueAnimator animation) {
   mLineLength = (float) animation.getAnimatedValue();
   invalidate();
  }
 });
 lineWidthAnim.addListener(new AnimatorListener() {
  @Override
  public void onAnimationEnd(Animator animation) {
   Log.d("@=>", "动画4结束");
   if (mStatus == STATUS_LOADING) {
    mStep++;
    startCRLCAnim();
   }
  }
 });
 lineWidthAnim.start();
 
 mAnimList.add(lineWidthAnim);
}
 
...
 
@Override
protected void onDraw(Canvas canvas) {
 super.onDraw(canvas);
 switch (mStep % 4) {
  ...
  case 3:
   for (int i = 0; i < mColors.length; i++) {
    mPaint.setColor(mColors[i]);
    drawLC(canvas, mWidth / 2 - mEntireLineLength / 2.2f, mHeight / 2 + mEntireLineLength, mWidth / 2 - mEntireLineLength / 2.2f, mHeight / 2 + mLineLength, mPaint, mCanvasAngle + i * 90);
   }
   break;
 }
 
}
 
...
 
private void drawLC(Canvas canvas, float startX, float startY, float stopX, float stopY, @NonNull Paint paint, int rotate) {
 canvas.rotate(rotate, mWidth / 2, mHeight / 2);
 canvas.drawArc(new RectF(startX - mCircleRadius, startY - mCircleRadius, startX + mCircleRadius, startY + mCircleRadius), 0, 180, true, mPaint);
 canvas.drawLine(startX, startY, stopX, stopY, paint);
 canvas.drawArc(new RectF(stopX - mCircleRadius, stopY - mCircleRadius, stopX + mCircleRadius, stopY + mCircleRadius), 180, 180, true, mPaint);
 canvas.rotate(-rotate, mWidth / 2, mHeight / 2);
}

动画4只做了线条的变化。

这样整个SlackLoading动画就完成了,是不是很简单。

以上就是本文的全部内容,希望对大家的学习有所帮助,也希望大家多多支持服务器之家。

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