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一步步教你寫Slack的Loading動畫

 更新時(shí)間：2016年09月09日 10:24:50   作者：jeasonwong  
這篇文章主要為大家詳細(xì)手摸手教你寫Slack的Loading動畫,具有一定的參考價(jià)值，感興趣的小伙伴們可以參考一下

項(xiàng)目地址：https://github.com/JeasonWong/SlackLoadingView

老規(guī)矩，先上效果。

圖好大。。

說下第一眼看到這個動畫后的思路：

+兩根平行線，要用到直線方程 y=kx+b
+另外兩根平行線，與之前兩根平行線的斜率相乘為-1，即k1*k2=-1
+線條做圓周運(yùn)動就是k值的不斷變化
+然后就是簡單的線條長度變化

我相信很多人第一眼會和我有類似的思路，但是當(dāng)我上了個廁所后意識到我想復(fù)雜了~

說下上完廁所后的思路：

不要想著線條是斜的，就是一個普通的線段，一個LineTo搞定（startX和stopX一樣，僅Y不同）
線條的垂直更容易，直接Canvas翻轉(zhuǎn)（轉(zhuǎn)過后再轉(zhuǎn)回）
整個動畫的圓周運(yùn)動也是Canvas翻轉(zhuǎn)（轉(zhuǎn)過后不轉(zhuǎn)回）
線條的單度變化依然用屬性動畫（這是必須的。。）
動畫開始前就讓整個Canvas旋轉(zhuǎn)
這樣一來就太容易了。

我把動畫分成了四步：

畫布旋轉(zhuǎn)及線條變化動畫（Canvas Rotate Line Change）
畫布旋轉(zhuǎn)動畫（Canvas Rotate）
畫布旋轉(zhuǎn)圓圈變化動畫（Canvas Rotate Circle Change）
線條變化動畫（Line Change）

詳細(xì)說明前先介紹下成員變量和一些初始化

成員變量

//靜止?fàn)顟B(tài)
 private final int STATUS_STILL = 0;
 //加載狀態(tài)
 private final int STATUS_LOADING = 1;
 //線條最大長度
 private final int MAX_LINE_LENGTH = dp2px(getContext(), 120);
 //線條最短長度
 private final int MIN_LINE_LENGTH = dp2px(getContext(), 40);
 //最大間隔時(shí)長
 private final int MAX_DURATION = 3000;
 //最小間隔時(shí)長
 private final int MIN_DURATION = 500;

 private Paint mPaint;
 private int[] mColors = new int[]{0xB07ECBDA, 0xB0E6A92C, 0xB0D6014D, 0xB05ABA94};
 private int mWidth, mHeight;
 //動畫間隔時(shí)長
 private int mDuration = MIN_DURATION;
 //線條總長度
 private int mEntireLineLength = MIN_LINE_LENGTH;
 //圓半徑
 private int mCircleRadius;
 //所有動畫
 private List<Animator> mAnimList = new ArrayList<>();
 //Canvas起始旋轉(zhuǎn)角度
 private final int CANVAS_ROTATE_ANGLE = 60;
 //動畫當(dāng)前狀態(tài)
 private int mStatus = STATUS_STILL;
 //Canvas旋轉(zhuǎn)角度
 private int mCanvasAngle;
 //線條長度
 private float mLineLength;
 //半圓Y軸位置
 private float mCircleY;
 //第幾部動畫
 private int mStep;

初始化

 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、畫布旋轉(zhuǎn)及線條變化動畫（Canvas Rotate Line Change）

 /**
  * Animation1
  * 動畫1
  * Canvas Rotate Line Change
  * 畫布旋轉(zhuǎn)及線條變化動畫
  */
 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("@=>", "動畫1結(jié)束");
    if (mStatus == STATUS_LOADING) {
     mStep++;
     startCRAnim();
    }
   }
  });
  animationSet.start();

  mAnimList.add(animationSet);
 }

第一步動畫涉及到兩個動畫同時(shí)進(jìn)行，所以使用了AnimatorSet，這個類很強(qiáng)大，可以讓N個動畫同時(shí)進(jìn)行（playTogether），也可以讓N個動畫順序執(zhí)行（playSequentially）。

說到這里，其實(shí)我的四個動畫就是順序進(jìn)行的，但是每個動畫里又有同時(shí)進(jìn)行的動畫，為了講解方便，我是監(jiān)聽了onAnimationEnd來控制動畫執(zhí)行順序，其實(shí)可以直接使用playSequentially。

上方動畫就干了兩件事：

1、旋轉(zhuǎn)畫布，從CANVAS_ROTATE_ANGLE + 0轉(zhuǎn)到CANVAS_ROTATE_ANGLE + 360，CANVAS_ROTATE_ANGLE是畫布初始傾斜角度

2、線條長度變化，從mEntireLineLength到-mEntireLineLength。

對應(yīng)的onDraw方法：

 @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);
 }

是不是很機(jī)智，drawCRLC做了三件事：

1、畫布旋轉(zhuǎn)后又旋轉(zhuǎn)回來

2、畫半圓（為什么要畫半圓？不畫整個圓？這里留個思考題。）

3、畫線條

這樣動畫1就完成了。

二、畫布旋轉(zhuǎn)動畫（Canvas Rotate）

 /**
  * Animation2
  * 動畫2
  * Canvas Rotate
  * 畫布旋轉(zhuǎn)動畫
  */
 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("@=>", "動畫2結(jié)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);
 }

有了動畫1的底子，那這個就太容易了，只是簡單的旋轉(zhuǎn)Canvas。

三、畫布旋轉(zhuǎn)圓圈變化動畫（Canvas Rotate Circle Change）

 /**
  * Animation3
  * 動畫3
  * Canvas Rotate Circle Change
  * 畫布旋轉(zhuǎn)圓圈變化動畫
  */
 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("@=>", "動畫3結(jié)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);
 }

動畫3做了兩件事：

1、旋轉(zhuǎn)Canvas

2、變化Circle的Y坐標(biāo)，達(dá)到往里縮的效果

四、線條變化動畫（Line Change）

 /**
  * Animation4
  * 動畫4
  * Line Change
  * 線條變化動畫
  */
 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("@=>", "動畫4結(jié)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);
 }

動畫4只做了線條的變化。

這樣整個Slack的Loading動畫就完成了，是不是很簡單。

以上就是本文的全部內(nèi)容，希望對大家的學(xué)習(xí)有所幫助，也希望大家多多支持腳本之家。

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