/*
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* Copyright (C) 2019 xuexiangjys(xuexiangjys@163.com)
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*
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* Licensed under the Apache License, Version 2.0 (the "License");
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* you may not use this file except in compliance with the License.
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* You may obtain a copy of the License at
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*
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* http://www.apache.org/licenses/LICENSE-2.0
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*
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* Unless required by applicable law or agreed to in writing, software
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* distributed under the License is distributed on an "AS IS" BASIS,
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* WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
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* See the License for the specific language governing permissions and
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* limitations under the License.
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*/
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package com.zhaoyang.driver.utils.citypickerview.picker.wheelview.timer;
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import com.zhaoyang.driver.utils.citypickerview.picker.wheelview.WheelView;
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import java.util.TimerTask;
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/**
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* 滚动惯性的实现
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*
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* @author 小嵩
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* date: 2017-12-23 23:20:44
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*/
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public final class InertiaTimerTask extends TimerTask {
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private float mCurrentVelocityY; //当前滑动速度
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private final float mFirstVelocityY;//手指离开屏幕时的初始速度
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private final WheelView mWheelView;
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/**
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* @param wheelView 滚轮对象
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* @param velocityY Y轴滑行速度
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*/
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public InertiaTimerTask(WheelView wheelView, float velocityY) {
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super();
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this.mWheelView = wheelView;
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this.mFirstVelocityY = velocityY;
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mCurrentVelocityY = Integer.MAX_VALUE;
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}
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@Override
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public final void run() {
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//防止闪动，对速度做一个限制。
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if (mCurrentVelocityY == Integer.MAX_VALUE) {
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if (Math.abs(mFirstVelocityY) > 2000F) {
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mCurrentVelocityY = mFirstVelocityY > 0 ? 2000F : -2000F;
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} else {
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mCurrentVelocityY = mFirstVelocityY;
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}
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}
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//发送handler消息 处理平顺停止滚动逻辑
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if (Math.abs(mCurrentVelocityY) >= 0.0F && Math.abs(mCurrentVelocityY) <= 20F) {
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mWheelView.cancelFuture();
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mWheelView.getHandler().sendEmptyMessage(MessageHandler.WHAT_SMOOTH_SCROLL);
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return;
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}
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int dy = (int) (mCurrentVelocityY / 100F);
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mWheelView.setTotalScrollY(mWheelView.getTotalScrollY() - dy);
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if (!mWheelView.isLoop()) {
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float itemHeight = mWheelView.getItemHeight();
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float top = (-mWheelView.getInitPosition()) * itemHeight;
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float bottom = (mWheelView.getItemsCount() - 1 - mWheelView.getInitPosition()) * itemHeight;
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if (mWheelView.getTotalScrollY() - itemHeight * 0.25 < top) {
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top = mWheelView.getTotalScrollY() + dy;
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} else if (mWheelView.getTotalScrollY() + itemHeight * 0.25 > bottom) {
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bottom = mWheelView.getTotalScrollY() + dy;
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}
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if (mWheelView.getTotalScrollY() <= top) {
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mCurrentVelocityY = 40F;
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mWheelView.setTotalScrollY((int) top);
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} else if (mWheelView.getTotalScrollY() >= bottom) {
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mWheelView.setTotalScrollY((int) bottom);
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mCurrentVelocityY = -40F;
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}
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}
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if (mCurrentVelocityY < 0.0F) {
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mCurrentVelocityY = mCurrentVelocityY + 20F;
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} else {
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mCurrentVelocityY = mCurrentVelocityY - 20F;
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}
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//刷新UI
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mWheelView.getHandler().sendEmptyMessage(MessageHandler.WHAT_INVALIDATE_LOOP_VIEW);
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}
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}
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