Android可自定義神奇動(dòng)效的卡片切換視圖實(shí)例

/*
 * ANIM_TYPE_FRONT:被選中的卡片通過(guò)自定義動(dòng)效移至第一，其他的卡片通過(guò)通用動(dòng)效補(bǔ)位
 * ANIM_TYPE_SWITCH:選中的卡片和第一張卡片互換位置，并都是自定義動(dòng)效
 * ANIM_TYPE_FRONT_TO_LAST:第一張圖片通過(guò)自定義動(dòng)效移至最后，其他卡片通過(guò)通用動(dòng)效補(bǔ)位
 */
public static final int ANIM_TYPE_FRONT = 0, ANIM_TYPE_SWITCH = 1, ANIM_TYPE_FRONT_TO_LAST = 2;

private CardAnimationHelper mAnimationHelper;
private BaseAdapter mAdapter;

private float mCardRatio = CARD_SIZE_RATIO;//寬高比：卡片高 / 卡片寬
private int mCardWidth, mCardHeight;//卡片寬高
@Override
protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
  ...
  if (mCardWidth == 0 || mCardHeight == 0) {
    setCardSize(true);
  }
}
/*
 * 根據(jù)卡片比例計(jì)算卡片寬高，并傳入Helper
 */
private void setCardSize(boolean resetAdapter) {
  mCardWidth = getMeasuredWidth();
  mCardHeight = (int) (mCardWidth * mCardRatio);
  mAnimationHelper.setCardSize(mCardWidth, mCardHeight);
  mAnimationHelper.initAdapterView(mAdapter, resetAdapter);
}

//卡片列表
private LinkedList<CardItem> mCards;
//當(dāng)前正在向后以及向前移動(dòng)的卡片
private CardItem mCardToBack, mCardToFront;
//正在向后以及向前移動(dòng)卡片的位置
private int mPositionToBack = 0, mPositionToFront = 0;
//動(dòng)畫(huà)運(yùn)行的ValueAnimator
private ValueAnimator mValueAnimator;
//當(dāng)前的動(dòng)畫(huà)系數(shù)
private float mCurrentFraction = 1;
...//以及一系列的轉(zhuǎn)換器與插值器

/**
 * ValueAnimator動(dòng)畫(huà)更新
 */
@Override
public void onAnimationUpdate(ValueAnimator animation) {
  //獲取當(dāng)前動(dòng)畫(huà)系數(shù)
  mCurrentFraction = (float) animation.getAnimatedValue();
  //通過(guò)插值器獲取插值系數(shù)
  fractionInterpolated = mAnimInterpolator.getInterpolation(mCurrentFraction);
  doAnimationCommon(mCurrentFraction, fractionInterpolated);
  ...
}

/**
 * 執(zhí)行通用動(dòng)畫(huà)
 */
private void doAnimationCommon(float fraction, float fractionInterpolated) {
  //如果當(dāng)前動(dòng)畫(huà)模式為選中的卡片移到最前
  if (mAnimType == InfiniteCardView.ANIM_TYPE_FRONT) {
    //則遍歷在選中卡片之前的卡片
    for (int i = 0; i < mPositionToFront; i++) {
      CardItem card = mCards.get(i);
      //對(duì)卡片執(zhí)行動(dòng)畫(huà)，從當(dāng)前位置移動(dòng)到后一個(gè)位置
      doAnimationCommonView(card.view, fraction, fractionInterpolated, i, i + 1);
      ...
    }
  }...
}

/**
 * 對(duì)視圖執(zhí)行通用動(dòng)畫(huà)
 * @param view         卡片視圖
 * @param fromPosition     從該位置
 * @param toPosition      移動(dòng)到該位置
 */
private void doAnimationCommonView(View view, float fraction, float fractionInterpolated, int
    fromPosition, int toPosition) {
  //通用轉(zhuǎn)換器轉(zhuǎn)換動(dòng)畫(huà)
  mTransformerCommon.transformAnimation(view, fraction, mCardWidth,
      mCardHeight, fromPosition, toPosition);
  if (mAnimInterpolator != null) {
    //通用轉(zhuǎn)換器轉(zhuǎn)換插值動(dòng)畫(huà)
    mTransformerCommon.transformInterpolatedAnimation(view, fractionInterpolated,            mCardWidth,mCardHeight, fromPosition, toPosition);
  }
}

@Override
public void transformAnimation(View view, float fraction, int cardWidth, int cardHeight, int fromPosition, int toPosition) {
  //需要跨越的卡片數(shù)量
  int positionCount = fromPosition - toPosition;
  //以0.8做為第一張的縮放尺寸，每向后一張縮小0.1
  //(0.8f - 0.1f * fromPosition) = 當(dāng)前位置的縮放尺寸
  //(0.1f * fraction * positionCount) = 移動(dòng)過(guò)程中需要改變的縮放尺寸
  float scale = (0.8f - 0.1f * fromPosition) + (0.1f * fraction * positionCount);
  ViewHelper.setScaleX(view, scale);
  ViewHelper.setScaleY(view, scale);
  //在Y方向的偏移量，每向后一張，向上偏移卡片寬度的0.02
  //-cardHeight * (0.8f - scale) * 0.5f 對(duì)卡片做整體居中處理
  ViewHelper.setTranslationY(view, -cardHeight * (0.8f - scale) * 0.5f - cardWidth * (0.02f *
     fromPosition - 0.02f * fraction * positionCount));
}