Recyclerview无限循环 横滑 第一item放大 pag

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• GitHub: @Ricco

ps：
产品提了一个需求，放大第一个item，可以左右滑动，无限循环，分页效果

自定义View

import android.content.Context;
import android.os.Handler;
import android.util.AttributeSet;
import android.view.View;

import androidx.annotation.NonNull;
import androidx.annotation.Nullable;
import androidx.lifecycle.Lifecycle;
import androidx.lifecycle.LifecycleObserver;
import androidx.lifecycle.OnLifecycleEvent;
import androidx.recyclerview.widget.LinearLayoutManager;
import androidx.recyclerview.widget.PagerSnapHelper;
import androidx.recyclerview.widget.RecyclerView;

/**
 * 支持自动滚动的无限横滑的第一个item放大效果的RecyclerView
 */
public class CustomRecyclerView extends RecyclerView implements LifecycleObserver {
    private int delayMillis = 3000;
    private Handler handler = null;
    private Runnable runnable = null;

    public CustomRecyclerView(@NonNull Context context) {
        super(context);
        init();
    }

    public CustomRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
        init();
    }

    public CustomRecyclerView(@NonNull Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init();
    }

    private void init() {
        setLayoutManager(new EnlargeLinearLayoutManager(getContext()));
        new PagerSnapHelper().attachToRecyclerView(this);
        handler = new Handler();
        runnable = new Runnable() {
            @Override
            public void run() {
                handler.postDelayed(this, delayMillis);
                View view = getChildAt(0);
                if (view != null) {
                    smoothScrollBy(view.getWidth(), 0);
                }
            }
        };
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_RESUME)
    private void resume() {
        if (handler != null) {
            handler.postDelayed(runnable, delayMillis);
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_PAUSE)
    private void pause() {
        if (handler != null) {
            handler.removeCallbacksAndMessages(null);
        }
    }

    @OnLifecycleEvent(Lifecycle.Event.ON_DESTROY)
    private void destroy() {
        if (handler != null) {
            handler.removeCallbacksAndMessages(null);
            handler = null;
        }
    }

    class EnlargeLinearLayoutManager extends LinearLayoutManager {

        EnlargeLinearLayoutManager(Context context) {
            super(context);
            setOrientation(HORIZONTAL);
            setReverseLayout(false);
        }

        @Override
        public int scrollHorizontallyBy(int dx, Recycler recycler, State state) {
            float d = 0f;
            float b = 0f;
            View view = findViewByPosition(findFirstVisibleItemPosition());
            if (view != null) {
                d = view.getPaddingTop() * 2f / view.getHeight();
                b = Math.abs(view.getX()) / view.getWidth();
                view.setScaleX(1 + d * (1 - b));
                view.setScaleY(1 + d * (1 - b));
            }
            View view2;
            if (dx > 0) {
                view2 = findViewByPosition(findFirstVisibleItemPosition() + 1);
            } else {
                view2 = findViewByPosition(findFirstCompletelyVisibleItemPosition());
            }
            if (view2 != null) {
                view2.setScaleX(1 + d * b);
                view2.setScaleY(1 + d * b);
            }
            return super.scrollHorizontallyBy(dx, recycler, state);
        }
    }
}

item.xml padding很重要

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/root"
    android:layout_width="120dp"
    android:layout_height="wrap_content"
    android:clipToPadding="true"
    android:orientation="vertical"
    android:paddingStart="8dp"
    android:paddingTop="10dp"
    android:paddingEnd="8dp"
    android:paddingBottom="10dp">

    <ImageView
        android:id="@+id/ivImg"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:adjustViewBounds="true"
        android:contentDescription="@null"
        android:src="@drawable/dou_test" />

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:gravity="center_horizontal"
        android:orientation="vertical">

        <TextView
            android:id="@+id/tvTitle"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="13dp"
            android:gravity="center"
            android:textColor="@color/dou_color3"
            android:textSize="12sp"
            tools:text="平台稳定安全" />

        <TextView
            android:id="@+id/tvContent"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="12dp"
            android:gravity="center"
            android:textColor="@color/dou_color6"
            android:textSize="10sp"
            tools:text="智能巡查+人工审核\n双重保障拒绝断缴" />
    </LinearLayout>
</FrameLayout>

adapter 主要实现无限循环

public class ItemAdapter extends BaseQuickAdapter<Item, BaseViewHolder> {
    public ItemAdapter () {
        super(R.layout.item);
    }

    @Override
    protected void convert(@NonNull BaseViewHolder holder, Itemitem) {
        if (item != null) {
            holder.setText(R.id.tvTitle, "" + item.getTitle())
                    .setText(R.id.tvContent, "" + item.getContent());
            Glide.with(mContext)
                    .load(item.getImg())
                    .into((ImageView) holder.getView(R.id.ivImg));
        }
    }

    @Override
    public int getItemCount() {
        return Short.MAX_VALUE;
    }

    @Override
    public HomeEntity.HomeArrBean getItem(int position) {
        if (getData().size() == 0) {
            return null;
        }
        int newPosition = position % getData().size();
        return getData().get(newPosition);
    }

    @Override
    public int getItemViewType(int position) {
        return 0;
    }

    @Override
    public void setNewData(@Nullable List<HomeEntity.HomeArrBean> data) {
        super.setNewData(data);
        if (data != null) {
            if (getRecyclerView() != null) {
                getRecyclerView().scrollToPosition(Short.MAX_VALUE / 2 / data.size() * data.size());
            }
        }
    }
}

activity，记得绑定lifecycle,及时销毁handler

adapter.bindToRecyclerView(rv);
getLifecycle().addObserver(rv);