1

二話不說(shuō)，上圖先淤毛！

RecyclerView已經(jīng)出來(lái)許久了今缚，估計(jì)現(xiàn)在沒(méi)多少人使用ListView或者GridView了吧？

這篇文章講解如何計(jì)算寬高相同或不同Item的RecyclerView滑動(dòng)距離低淡，所謂的滑動(dòng)距離意思如下圖姓言。

大概思路就是先得出正在移出屏幕Item的

position，再得出該Item的寬或高蔗蹋，再得出該Item還有多少部分未移出屏幕何荚，拿

position乘寬或者高減去未移出屏幕的距離，就可以算出滑動(dòng)的距離了(?????)

先看下定義的變量和常量

//豎著
private static final int MANAGER_LINEAR_VERTICAL = 0;
//橫著一行
private static final int MANAGER_LINEAR_HORIZONTAL = 1;
//Grid 豎著
private static final int MANAGER_LINEAR_GRIDVIEW_VERTICAL = 2;
//Grid 橫著
private static final int MANAGER_LINEAR_GRIDVIEW_HORIZONTAL = 3;
//豎著不同
private static final int MANAGER_LINEAR_VERTICAL_ = 4;
//橫著不同
private static final int MANAGER_LINEAR_HORIZONTAL_ = 5;
//形態(tài)變量
private int intType = 0;
//item的寬/高
private int itemW;
private int itemH;
private int iResult;
//存放item寬或高
private Map<Integer, Integer> mMapList = new HashMap<>();
private int iposition;

Item布局

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
                android:layout_width="wrap_content"
                android:layout_height="wrap_content">
    <ImageView
        android:id="@+id/iv"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@mipmap/ic_tk"/>
    <TextView
        android:id="@+id/tv_position"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/iv"
        android:layout_alignTop="@+id/iv"
        android:background="@color/colorPrimary"
        android:textColor="#e5e5e6"
    />
</RelativeLayout>

一猪杭、計(jì)算寬高相同Item

//該方法用于監(jiān)聽(tīng)mRecyclerView的滑動(dòng)事件
mRecyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
    @Override
    public void onScrolled(RecyclerView recyclerView, int dx, int dy) {
        super.onScrolled(recyclerView, dx, dy);
    }
});

在上面監(jiān)聽(tīng)中調(diào)用下面計(jì)算方法餐塘，可計(jì)算出VERTICAL豎著布局的滑動(dòng)距離

//找到即將移出屏幕Item的position,position是移出屏幕item的數(shù)量
int position = linearLayoutManager.findFirstVisibleItemPosition();
//根據(jù)position找到這個(gè)Item
View firstVisiableChildView = linearLayoutManager.findViewByPosition(position);
//獲取Item的高
int itemHeight = firstVisiableChildView.getHeight();
//算出該Item還未移出屏幕的高度
int itemTop = firstVisiableChildView.getTop();
//position移出屏幕的數(shù)量*高度得出移動(dòng)的距離
int iposition = position * itemHeight;
//減去該Item還未移出屏幕的部分可得出滑動(dòng)的距離
iResult = iposition - itemTop;

若是HORIZONTAL橫著的RecyclerView則需要稍加改動(dòng)調(diào)用下面方法就能計(jì)算出滑動(dòng)距離因?yàn)槭菣M著的所以要拿到item的寬，用getRight()方法算出未移出屏幕的距離皂吮，但橫著的RecyclerView取到的第一個(gè)Item Position為零戒傻，所以隨后算總距離的時(shí)候要加上一個(gè)Item的寬度

//找到即將移出屏幕Item的position,position是移出屏幕item的數(shù)量
int position = linearLayoutManager.findFirstVisibleItemPosition();
//根據(jù)position找到這個(gè)Item
View firstVisiableChildView = linearLayoutManager.findViewByPosition(position);
//獲取Item的寬
int itemWidth = firstVisiableChildView.getWidth();
//算出該Item還未移出屏幕的高度
int itemRight = firstVisiableChildView.getRight();
//position移出屏幕的數(shù)量*高度得出移動(dòng)的距離
int iposition = position * itemWidth;
//因?yàn)闄M著的RecyclerV第一個(gè)取到的Item position為零所以計(jì)算時(shí)需要加一個(gè)寬
iResult = iposition - itemRight + itemWidth;

二、計(jì)算Grid排列相同Item

豎著的Grid蜂筹，注釋很認(rèn)真的寫(xiě)了(⊙o⊙)需纳，大部分還是一樣的

//得出spanCount幾列或幾排
int itemSpanCount = gridLayoutManager.getSpanCount();
//得出的position是一排或一列總和
int position = gridLayoutManager.findFirstVisibleItemPosition();
//需要算出才是即將移出屏幕Item的position
int itemPosition = position / itemSpanCount ;
//因?yàn)槭窍嗤腎tem所以取那個(gè)都一樣
View firstVisiableChildView = gridLayoutManager.findViewByPosition(position);
int itemHeight = firstVisiableChildView.getHeight();
int itemTop = firstVisiableChildView.getTop();
int iposition = itemPosition * itemHeight;
iResult = iposition - itemTop;

橫著的Grid大家可以下Demo看一下，也是有注釋的

三狂票、計(jì)算不同Item

思路：用Map按Position記錄了每個(gè)Item的寬或高候齿，通過(guò)

findFirstVisibleItemPosition（）方法動(dòng)態(tài)計(jì)算滑動(dòng)距離

public int unlikeVertical() {
    int itemWH = 0;
    int itemTR = 0;
    int distance = 0;
    int position = linearLayoutManager.findFirstVisibleItemPosition();
    View firstVisiableChildView = linearLayoutManager.findViewByPosition(position);
    //判斷是橫著還是豎著，得出寬或高
    if (intType == MANAGER_LINEAR_VERTICAL_) {
        itemWH = firstVisiableChildView.getHeight();
    } else if (intType == MANAGER_LINEAR_HORIZONTAL_) {
        itemWH = firstVisiableChildView.getWidth();
    }
    //一層判斷mMapList是否為空闺属，若不為空則根據(jù)鍵判斷保證不會(huì)重復(fù)存入
    if (mMapList.size() == 0) {
        mMapList.put(position, itemWH);
    } else {
        if (!mMapList.containsKey(position)) {
            mMapList.put(position, itemWH);
            Log.d("poi", mMapList + "");
        }
    }
    //判斷是橫著還是豎著慌盯，得出未滑出屏幕的距離
    if (intType == MANAGER_LINEAR_VERTICAL_) {
        itemTR = firstVisiableChildView.getTop();
    } else if (intType == MANAGER_LINEAR_HORIZONTAL_) {
        itemTR = firstVisiableChildView.getRight();
    }
    //position為動(dòng)態(tài)獲取，目前屏幕Item位置
    for (int i = 0; i < position; i++) {
        //iposition移出屏幕的距離
        iposition = iposition + mMapList.get(i);
    }
    //根據(jù)類(lèi)型拿iposition減未移出Item部分距離掂器，最后得出滑動(dòng)距離
    if (intType == MANAGER_LINEAR_VERTICAL_) {
        distance = iposition - itemTR;
    } else if (intType == MANAGER_LINEAR_HORIZONTAL_) {
        distance = iposition - itemTR + itemWH;
    }
    //item寬高
    itemW = firstVisiableChildView.getWidth();
    itemH = firstVisiableChildView.getHeight();
    //歸零
    iposition = 0;
    return distance;
}

Demo地址：github.com/NathansLiu/…

My JianShu：www.reibang.com/u/ae7a687f5…

My JueJin：https://juejin.im/user/59a0ca42f265da2491510f10

寫(xiě)完啦亚皂！

3