Android自定义View新年烟花、祝福语横幅动画

Z时代
2024-01-10
分类：综合

新年了，项目中要作个动画，整体要求实现彩带乱飞，烟花冲天而起，烟花缩放，小鸡换图，小鸡飘移，横幅裁剪、展开等动画效果，全局大量使用了属性动画来实现。

如下效果图：

我在实现过程中，横幅的裁剪计算，捣腾了比较久的时间，初版采用属性动画计算float的一个比率值，来配合每一帧的裁剪绘制，如下代码：


private static class RollView extends View { 
 private Bitmap mBitmap; 
 private Rect mSrc; 
 private Rect mDst; 
 private int mRollWidth = 60; 
 private float mRate; 
 private boolean mIsStopAnim; 
 public RollView(Context context) { 
  super(context); 
  mSrc = new Rect(); 
  mDst = new Rect(); 
 } 
 @Override 
 protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) { 
  super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
 } 
 @Override 
 protected void onDraw(Canvas canvas) { 
  if (mBitmap == null) return; 
  drawFromMiddleByFloatCompute(canvas); 
 } 
 private void drawFromMiddleByFloatCompute(Canvas canvas) { 
  /* 
  以下src 都需要加上mBitmap. 的前缀，， 因从drawable拿到的是原始图片宽高 
  而适配时，可能view的宽高比 drawable的宽高还小或大 
  */ 
  final float rate = mRate; 
  mSrc.left = 0; 
  mSrc.top = 0; 
  mSrc.right = mRollWidth; 
  mSrc.bottom = mBitmap.getHeight(); 
  mDst.left = (int) ((getWidth() / 2 - mRollWidth) - (getWidth() / 2 - mRollWidth) * rate); 
  mDst.top = 0; 
  mDst.right = mDst.left + mRollWidth + 1;//因精度问题，这里强制+1 
  mDst.bottom = getHeight(); 
  canvas.drawBitmap(mBitmap, mSrc, mDst, null); 
  //中间 
  int sw = (int) ((mBitmap.getWidth() - mRollWidth * 2) * rate); 
  mSrc.left = mBitmap.getWidth() / 2 - sw / 2; 
  mSrc.top = 0; 
  mSrc.right = mSrc.left + sw; 
  mSrc.bottom = mBitmap.getHeight(); 
  int dw = (int) ((getWidth() - mRollWidth * 2) * rate); 
  mDst.left = getWidth() / 2 - dw / 2; 
  mDst.top = 0; 
  mDst.right = mDst.left + dw; 
  mDst.bottom = getHeight(); 
  canvas.drawBitmap(mBitmap, mSrc, mDst, null); 
  //右边 
  mSrc.left = mBitmap.getWidth() - mRollWidth; 
  mSrc.top = 0; 
  mSrc.right = mBitmap.getWidth(); 
  mSrc.bottom = mBitmap.getHeight(); 
  mDst.left = (int) (getWidth() / 2 + (getWidth() / 2 - mRollWidth) * rate); 
  mDst.top = 0; 
  mDst.right = mDst.left + mRollWidth; 
  mDst.bottom = getHeight(); 
  canvas.drawBitmap(mBitmap, mSrc, mDst, null); 
 } 
 public void setRes(int resId) { 
  mBitmap = getBitmapFromLocal(resId); 
 } 
 @RequiresApi(api = Build.VERSION_CODES.HONEYCOMB) 
 public void startFloatComputeAnim() { 
  /* 
  如果有float获取比率值，从而计算出相应的坐标值，那么可能由于最终在转成Rect的坐标时， 
  float to int ，有精度的损失：1个px 而引起效果的不理想 
  */ 
  ValueAnimator animator = ValueAnimator.ofFloat(0, 1); 
  animator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() { 
  @Override 
  public void onAnimationUpdate(ValueAnimator animation) { 
   if (mIsStopAnim) { 
   animation.cancel(); 
   return; 
   } 
   mRate = (float) animation.getAnimatedValue(); 
   invalidate(); 
  } 
  }); 
  animator.setDuration(2000); 
  animator.start(); 
 } 
 public void stopAnim() { 
  mIsStopAnim = true; 
 } 
 }