/**
*
* 使用ScalePosition 需要先设置Model为MODEL_NOT_POSITION，设置SCALE_START 那么第一个可见view 会放大scaleRatio 其余的大小不变
* 设置为SCALE_CENTER 那么中间的保持原始大小 两边的距离越远 大小与越小
*
* Model 设置MODEL_POINT_POSITION 那么可以指定currentPosition 那么指定的currentPosition对饮的view 就会放大scaleRatio 其余的不变
*/
public class StackLayoutManager extends RecyclerView.LayoutManager {
/**
* 一次完整的聚焦滑动所需要的移动距离
*/
private float onceCompleteScrollLength = -1;
/**
* 第一个子view的偏移量
*/
private float firstChildCompleteScrollLength = -1;
/**
* 屏幕可见第一个view的position
*/
private int mFirstVisiPos;
/**
* 屏幕可见的最后一个view的position
*/
private int mLastVisiPos;
/**
* 水平方向累计偏移量
*/
private long mHorizontalOffset;
/**
* 普通view之间的margin
*/
private float normalViewGap = 0;
private int childWidth = 0;
/*指定放大的item 下标固定不不变*/
public static final int MODEL_POINT_POSITION = 0;
/*不指定下标 滑动到指定位置 的放大*/
public static final int MODEL_NOT_POSITION = 1;
private int currentModel = 0;
/*指定当前放大的position*/
private int currentPosition = 0;
private float scaleRatio = 1;
@IntDef({MODEL_POINT_POSITION,MODEL_NOT_POSITION})
@Retention(RetentionPolicy.SOURCE)
public @interface Model{}
/*放大的位置在开始*/
public static final int SCALE_START = 0;
/*放大的位置居中*/
public static final int SCALE_CENTER = 1;
/*在开头放大 还是在居中放大*/
private int scalePosition = 0;
@IntDef({SCALE_START,SCALE_CENTER})
@Retention(RetentionPolicy.SOURCE)
public @interface ScalePosition{}
/**
* 是否自动选中
*/
private boolean isAutoSelect = false;
private ValueAnimator selectAnimator;
@Override
public RecyclerView.LayoutParams generateDefaultLayoutParams() {
return new RecyclerView.LayoutParams(RecyclerView.LayoutParams.WRAP_CONTENT, RecyclerView.LayoutParams.WRAP_CONTENT);
}
public StackLayoutManager(Context context, int gap) {
normalViewGap = dp2px(context, gap);
}
public StackLayoutManager(Context context) {
this(context, 0);
}
public static float dp2px(Context context, float dp) {
return TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp,
context.getResources().getDisplayMetrics());
}
@Override
public void onLayoutChildren(RecyclerView.Recycler recycler, RecyclerView.State state) {
// super.onLayoutChildren(recycler, state);
if (state.getItemCount() == 0) {
removeAndRecycleAllViews(recycler);
return;
}
onceCompleteScrollLength = -1;
// 分离全部已有的view 放入临时缓存 mAttachedScrap 集合中
detachAndScrapAttachedViews(recycler);
fill(recycler, state, 0);
}
private int fill(RecyclerView.Recycler recycler, RecyclerView.State state, int dx) {
int resultDelta = dx;
resultDelta = fillHorizontalLeft(recycler, state, dx);
recycleChildren(recycler);
return resultDelta;
}
@Override
public boolean canScrollHorizontally() {
return true;
}
@Override
public int scrollHorizontallyBy(int dx, RecyclerView.Recycler recycler, RecyclerView.State state) {
// 手指从右向左滑动，dx > 0; 手指从左向右滑动，dx < 0;
// 位移0、没有子View 当然不移动
if (dx == 0 || getChildCount() == 0) {
return 0;
}
float realDx = dx / 1.0f;
if (Math.abs(realDx) < 0.00000001f) {
return 0;
}
mHorizontalOffset += dx;
dx = fill(recycler, state, dx);
return dx;
}
/**
* 最大偏移量
*
* @return
*/
private float getMaxOffset() {
if (childWidth == 0 || getItemCount() == 0) return 0;
// getWidth() / 2 + childWidth / 2 +
float max = (childWidth + normalViewGap)*(getItemCount()) -getWidth()+childWidth*(scaleRatio-1);
// return (childWidth + normalViewGap) * (getItemCount() - 1);
return max >0 ? max :0;
}
/**
* 获取最小的偏移量
*
* @return
*/
private float getMinOffset() {
if (childWidth == 0) return 0;
// return (getWidth() - childWidth) / 2;
return 0;
}
private int fillHorizontalLeft(RecyclerView.Recycler recycler, RecyclerView.State state, int dx) {
//----------------1、边界检测-----------------
if (dx < 0) {
// 已到达左边界
if (mHorizontalOffset < 0) {
mHorizontalOffset = dx = 0;
}
}
if (dx > 0) {
if (mHorizontalOffset >= getMaxOffset()) {
// 因为在因为scrollHorizontallyBy里加了一次dx，现在减回去
// mHorizontalOffset -= dx;
mHorizontalOffset = (long) getMaxOffset();
dx = 0;
}
}
// 分离全部的view，加入到临时缓存
detachAndScrapAttachedViews(recycler);
float startX = 0;
float fraction = 0f;
boolean isChildLayoutLeft = true;
View tempView = null;
int tempPosition = -1;
if (onceCompleteScrollLength == -1) {
// 因为mFirstVisiPos在下面可能被改变，所以用tempPosition暂存一下
tempPosition = mFirstVisiPos;
tempView = recycler.getViewForPosition(tempPosition);
measureChildWithMargins(tempView, 0, 0);
childWidth = getDecoratedMeasurementHorizontal(tempView);
}
// 修正第一个可见view mFirstVisiPos 已经滑动了多少个完整的onceCompleteScrollLength就代表滑动了多少个item
firstChildCompleteScrollLength = childWidth ;
if (mHorizontalOffset >= firstChildCompleteScrollLength) {
startX = normalViewGap;
onceCompleteScrollLength = childWidth + normalViewGap;
mFirstVisiPos = (int) Math.floor(Math.abs(mHorizontalOffset - firstChildCompleteScrollLength) / onceCompleteScrollLength) + 1;
/*计算第一个可见的view 偏移的距离*/
fraction = (Math.abs(mHorizontalOffset - firstChildCompleteScrollLength) % onceCompleteScrollLength) / (onceCompleteScrollLength * 1.0f);
} else {
mFirstVisiPos = 0;
startX = getMinOffset();
onceCompleteScrollLength = firstChildCompleteScrollLength;
fraction = (Math.abs(mHorizontalOffset) % onceCompleteScrollLength) / (onceCompleteScrollLength * 1.0f);
}
// 临时将mLastVisiPos赋值为getItemCount() - 1，放心，下面遍历时会判断view是否已溢出屏幕，并及时修正该值并结束布局
mLastVisiPos = getItemCount() - 1;
float normalViewOffset = onceCompleteScrollLength * fraction;
boolean isNormalViewOffsetSetted = false;
//----------------3、开始布局-----------------
for (int i = mFirstVisiPos; i <= mLastVisiPos; i++) {
View item;
if (i == tempPosition && tempView != null) {
// 如果初始化数据时已经取了一个临时view 这里只是避免去取第一个view 已经拿出来过一次
item = tempView;
} else {
item = recycler.getViewForPosition(i);
}
int focusPosition = (int) (Math.abs(mHorizontalOffset) / (childWidth + normalViewGap));
/*这里只影响显示的先后顺序 不影响拜访位置的顺序*/
if (i <= focusPosition) {
addView(item);
} else {
addView(item, 0);
}
measureChildWithMargins(item, 0, 0);
/*只有第一个view 需要计算 后续的直接 累加*/
if (!isNormalViewOffsetSetted) {
startX -= normalViewOffset;
isNormalViewOffsetSetted = true;
}
int l, t, r, b;
l = (int) startX;
t = getPaddingTop();
r = l + getDecoratedMeasurementHorizontal(item);
b = t + getDecoratedMeasurementVertical(item);
if(currentModel == MODEL_POINT_POSITION){
if(i == currentPosition){
item.setPivotX(0);
item.setPivotY(getDecoratedMeasurementVertical(item));
item.setScaleX(scaleRatio);
item.setScaleY(scaleRatio);
}
}else{
// 缩放子view
final float minScale = 0.6f;
float currentScale = 0f;
final int childCenterX = (r + l) / 2;
final int parentCenterX = getCenterX();
if(scalePosition == SCALE_START){
/*如果是开头放大*/
if(childCenterX <= getCenterX()){
item.setScaleX(scaleRatio);
item.setScaleY(scaleRatio);
}else {
item.setScaleX(1);
item.setScaleY(1);
};
}else {
isChildLayoutLeft = childCenterX <= parentCenterX;
if (isChildLayoutLeft) {
final float fractionScale = (parentCenterX - childCenterX) / (parentCenterX * 1.0f);
currentScale = 1.0f - (1.0f - minScale) * fractionScale;
} else {
final float fractionScale = (childCenterX - parentCenterX) / (parentCenterX * 1.0f);
currentScale = 1.0f - (1.0f - minScale) * fractionScale;
}
item.setScaleX(currentScale);
item.setScaleY(currentScale);
}
}
layoutDecoratedWithMargins(item, l, t, r, b);
/*如果是选中的view 需要添加放大的偏移*/
if(i == currentPosition && currentModel == MODEL_POINT_POSITION){
startX += (childWidth*scaleRatio + normalViewGap);
}else{
startX += (childWidth + normalViewGap);
}
if (startX > getWidth() - getPaddingRight()) {
mLastVisiPos = i;
break;
}
}
return dx;
}
@Override
public void onScrollStateChanged(int state) {
super.onScrollStateChanged(state);
switch (state) {
case RecyclerView.SCROLL_STATE_DRAGGING:
//当手指按下时，停止当前正在播放的动画
cancelAnimator();
break;
case RecyclerView.SCROLL_STATE_IDLE:
//当列表滚动停止后，判断一下自动选中是否打开
if (isAutoSelect) {
//找到离目标落点最近的item索引 是否滑动到指定Position
smoothScrollToPosition(findShouldSelectPosition(), null);
}
break;
default:
break;
}
}
public int findShouldSelectPosition() {
if (onceCompleteScrollLength == -1 || mFirstVisiPos == -1) {
return -1;
}
int position = (int) (Math.abs(mHorizontalOffset) / (childWidth + normalViewGap));
int remainder = (int) (Math.abs(mHorizontalOffset) % (childWidth + normalViewGap));
// 超过一半，应当选中下一项
if (remainder >= (childWidth + normalViewGap) / 2.0f) {
if (position + 1 <= getItemCount() - 1) {
return position + 1;
}
}
return position;
}
/**
* 平滑滚动到某个位置
*
* @param position 目标Item索引
*/
public void smoothScrollToPosition(int position, OnStackListener listener) {
if (position > -1 && position < getItemCount()) {
startValueAnimator(position, listener);
}
}
private void startValueAnimator(int position, final OnStackListener listener) {
cancelAnimator();
final float distance = getScrollToPositionOffset(position);
long minDuration = 100;
long maxDuration = 300;
long duration;
float distanceFraction = (Math.abs(distance) / (childWidth + normalViewGap));
if (distance <= (childWidth + normalViewGap)) {
duration = (long) (minDuration + (maxDuration - minDuration) * distanceFraction);
} else {
duration = (long) (maxDuration * distanceFraction);
}
selectAnimator = ValueAnimator.ofFloat(0.0f, distance);
selectAnimator.setDuration(duration);
selectAnimator.setInterpolator(new LinearInterpolator());
final float startedOffset = mHorizontalOffset;
selectAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
@Override
public void onAnimationUpdate(ValueAnimator animation) {
float value = (float) animation.getAnimatedValue();
mHorizontalOffset = (long) (startedOffset + value);
requestLayout();
}
});
selectAnimator.addListener(new AnimatorListenerAdapter() {
@Override
public void onAnimationEnd(Animator animation) {
super.onAnimationEnd(animation);
if (listener != null) {
listener.onFocusAnimEnd();
}
}
});
selectAnimator.start();
}
/**
* @param position
* @return
*/
private float getScrollToPositionOffset(int position) {
return position * (childWidth + normalViewGap) - Math.abs(mHorizontalOffset);
}
/**
* 取消动画
*/
public void cancelAnimator() {
if (selectAnimator != null && (selectAnimator.isStarted() || selectAnimator.isRunning())) {
selectAnimator.cancel();
}
}
/**
* 回收需回收的item
*/
private void recycleChildren(RecyclerView.Recycler recycler) {
List<RecyclerView.ViewHolder> scrapList = recycler.getScrapList();
for (int i = 0; i < scrapList.size(); i++) {
RecyclerView.ViewHolder holder = scrapList.get(i);
removeAndRecycleView(holder.itemView, recycler);
}
}
/**
* 获取某个childView在水平方向所占的空间，将margin考虑进去
*
* @param view
* @return
*/
public int getDecoratedMeasurementHorizontal(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return getDecoratedMeasuredWidth(view) + params.leftMargin
+ params.rightMargin;
}
/**
* 获取某个childView在竖直方向所占的空间,将margin考虑进去
*
* @param view
* @return
*/
public int getDecoratedMeasurementVertical(View view) {
final RecyclerView.LayoutParams params = (RecyclerView.LayoutParams)
view.getLayoutParams();
return getDecoratedMeasuredHeight(view) + params.topMargin
+ params.bottomMargin;
}
public int getVerticalSpace() {
return getHeight() - getPaddingTop() - getPaddingBottom();
}
public int getHorizontalSpace() {
return getWidth() - getPaddingLeft() - getPaddingRight();
}
public interface OnStackListener {
void onFocusAnimEnd();
}
public void setModel(@Model int model){
currentModel = model;
}
public void setPosition(int currentPosition){
this.currentPosition = currentPosition;
}
public void setScaleRatio(float scaleRatio){
this.scaleRatio = scaleRatio;
}
public void setScaleModel(@ScalePosition int scalePosition){
this.scalePosition = scalePosition;
}
public void isAutoSelect(boolean isAutoSelect){
this.isAutoSelect = isAutoSelect;
}
private int getCenterX(){
return scalePosition == SCALE_START ? childWidth/2 : getWidth()/2;
}
@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
LinearSmoothScroller linearSmoothScroller =
new LinearSmoothScroller(recyclerView.getContext());
linearSmoothScroller.setTargetPosition(position);
startSmoothScroll(linearSmoothScroller);
}
}
网友评论