一、创建RecyclerView居中管理的Manager
// 默认线性布局
public class CenterLayoutManager extends LinearLayoutManager {
public CenterLayoutManager(Context context) {
super(context);
}
public CenterLayoutManager(Context context, int orientation, boolean reverseLayout) {
super(context, orientation, reverseLayout);
}
public CenterLayoutManager(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
super(context, attrs, defStyleAttr, defStyleRes);
}
@Override
public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
RecyclerView.SmoothScroller smoothScroller = new CenterSmoothScroller(recyclerView.getContext());
smoothScroller.setTargetPosition(position);
startSmoothScroll(smoothScroller);
}
private static class CenterSmoothScroller extends LinearSmoothScroller {
CenterSmoothScroller(Context context) {
super(context);
}
@Override
public int calculateDtToFit(int viewStart, int viewEnd, int boxStart, int boxEnd, int snapPreference) {
return (boxStart + (boxEnd - boxStart) / 2) - (viewStart + (viewEnd - viewStart) / 2);
}
}
}
二、创建Item的Decoration
DeviceUtils 主要使用px2dip进行换算距离，可以将DeviceUtils.px2dip替换成网上任意的工具类换算
public class GalleryItemDecoration extends RecyclerView.ItemDecoration {
/**
* 自定义默认的Item的边距
*/
private int mPageMargin = 10;
/**
* 第一张图片的左边距
*/
private int mLeftPageVisibleWidth;
@Override
public void getItemOffsets(Rect outRect, View view, RecyclerView parent, RecyclerView.State state) {
//计算一下第一中图片距离屏幕左边的距离：(屏幕的宽度-item的宽度)/2。其中item的宽度=实际ImagView的宽度+margin。
//我这里设置的ImageView的宽度为100+margin=110
if (mLeftPageVisibleWidth ==0) {
//计算一次就好了
mLeftPageVisibleWidth = DeviceUtils.px2dip(view.getContext(),getScreenWidth(view.getContext()) - DeviceUtils.dip2px(view.getContext(), 110)) / 2;
}
//获取当前Item的position
int position = parent.getChildAdapterPosition(view);
//获得Item的数量
int itemCount = parent.getAdapter().getItemCount();
int leftMargin;
if (position == 0){
leftMargin= dpToPx(mLeftPageVisibleWidth);
}else{
leftMargin=dpToPx(mPageMargin);
}
int rightMagin;
if (position == itemCount-1) {
rightMagin=dpToPx(mLeftPageVisibleWidth);
}else{
rightMagin=dpToPx(mPageMargin);
}
RecyclerView.LayoutParams layoutParams = (RecyclerView.LayoutParams) view.getLayoutParams();
//10,10分别是item到上下的margin
layoutParams.setMargins(leftMargin,10,rightMagin,10);
view.setLayoutParams(layoutParams);
super.getItemOffsets(outRect, view, parent, state);
}
/**
* d p转换成px
* @param dp：
*/
private int dpToPx(int dp){
return (int) (dp * Resources.getSystem().getDisplayMetrics().density + 0.5f);
}
/**
* 获取屏幕的宽度
* @param context:
* @return :
*/
public static int getScreenWidth(Context context) {
WindowManager manager = (WindowManager) context
.getSystemService(Context.WINDOW_SERVICE);
Display display = manager.getDefaultDisplay();
return display.getWidth();
}
}
三、具体使用
// 列表
@BindView(R.id.rlxxx)
RecyclerView mRecyclerView;
private XXXXAdapter mXXXXAdapter ; // 原生Adapter就行
private LinearSnapHelper mLinearSnapHelper;
private CenterLayoutManager mCenterLayoutManager;
----------------------------------------------------------------------
mLinearSnapHelper = new LinearSnapHelper();
mLinearSnapHelper.attachToRecyclerView(mRecyclerView);
mXXXXAdapter = new XXXXAdapter (addData());
mCenterLayoutManager = new CenterLayoutManager(getContext(), LinearLayoutManager.HORIZONTAL, false);
mRecyclerView.setLayoutManager(mCenterLayoutManager);
mRecyclerView.setAdapter(mSignInAdapter);
mRecyclerView.addItemDecoration(new GalleryItemDecoration());
四、XML
<android.support.v7.widget.RecyclerView
android:id="@+id/rlxxx"
android:orientation="horizontal"
tools:itemCount="7"
tools:layoutManager="LinearLayoutManager"
tools:listitem="@layout/item_xxx_layout"
android:layout_width="wrap_content"
android:layout_height="wrap_content"/>