RecycleView实现轮播图

学了好久，终于实现了。分享一下代码吧。

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
    xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical">
    <LinearLayout
        android:layout_width="wrap_content"
        android:layout_height="wrap_content">
        <include
        layout="@layout/titlebar_home" />
    </LinearLayout>
    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_marginLeft="@dimen/horizontal_dimen_10dp"
        android:layout_marginRight="@dimen/horizontal_dimen_10dp"
        android:layout_height="wrap_content">
        <android.support.v7.widget.RecyclerView
            android:id="@+id/recycler"
            android:layout_width="match_parent"
            android:layout_height="200dp"
            android:layout_alignParentStart="true"
            android:layout_marginStart="0dp"></android.support.v7.widget.RecyclerView>

        <com.example.bs.Home.BannerIndicator
            android:id="@+id/indicator"
            android:layout_width="match_parent"
            android:layout_height="32dp"
            android:layout_alignBottom="@+id/recycler"
            app:selectColor="@color/colorAccent"
            app:unselectedColor="#ffffff"
            app:radius="3dp"
            app:space="10dp"/>
    </RelativeLayout>


</LinearLayout>

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package com.example.bs.Home;

import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.RecyclerView;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.bumptech.glide.Glide;
import com.example.bs.R;

import java.util.List;

public class BannerAdapter extends RecyclerView.Adapter<BannerAdapter.ViewHolder> {

    private List<Integer> list;
    private Context context;

    public BannerAdapter(Context context, List<Integer> list){
        this.list=list;
        this.context=context;
    }

    @Override
    public ViewHolder onCreateViewHolder(@NonNull ViewGroup parent, int viewType) {
        View view= LayoutInflater.from(parent.getContext()).inflate(R.layout.item_image,parent,false);
        return new ViewHolder(view);
    }

    @Override
    public void onBindViewHolder(@NonNull ViewHolder holder, int position) {
        Glide.with(context).load(list.get(position%list.size())).into(holder.imageView);
    }

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

    class ViewHolder extends RecyclerView.ViewHolder {
        private ImageView imageView;

        public ViewHolder(View itemView) {
            super(itemView);
            imageView= (ImageView) itemView.findViewById(R.id.item_image);
        }

    }
}

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package com.example.bs.Home;

import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.support.annotation.Nullable;
import android.util.AttributeSet;
import android.view.View;

import com.example.bs.R;

public class BannerIndicator extends View {
    private int number;
    private int position = 0;
    private Paint paint = new Paint();
    private int selectColor;
    private int unSelectColor;
    private float radius;
    private float space;

    public BannerIndicator(Context context) {
        this(context,null);
    }

    public BannerIndicator(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);

        TypedArray typedArray = context.obtainStyledAttributes(attrs, R.styleable.BannerIndicator);
        this.selectColor = typedArray.getColor(R.styleable.BannerIndicator_selectColor, Color.RED);
        this.unSelectColor = typedArray.getColor(R.styleable.BannerIndicator_unselectedColor, Color.BLACK);
        this.radius = typedArray.getDimension(R.styleable.BannerIndicator_radius, 10);
        this.space = typedArray.getDimension(R.styleable.BannerIndicator_space, 20);
        typedArray.recycle();

    }

    {
        paint.setStyle(Paint.Style.FILL);
        paint.setAntiAlias(true);
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);

        float startPosition = getWidth() / 2 - (radius * 2 * number + space * (number - 1)) / 2;

        canvas.save();
        for (int i = 0; i < number; i++) {
            if (i == position) {
                paint.setColor(selectColor);
            } else {
                paint.setColor(unSelectColor);
            }
            canvas.drawCircle(startPosition + radius * (2 * i + 1) + i * space, getHeight() / 2, radius, paint);
        }
        canvas.restore();

    }

    public void setNumber(int number) {
        this.number = number;
    }

    public void setPosition(int position) {
        this.position = position;
        invalidate();
    }
}

——----------------------------------------------------------------------------

package com.example.bs.Home;

import android.content.Context;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.LinearSmoothScroller;
import android.support.v7.widget.RecyclerView;
import android.util.DisplayMetrics;

/**
 * author Gao
 * date 2017/11/23 0023
 * description
 */

public class SmoothLinearLayoutManager extends LinearLayoutManager {

    public SmoothLinearLayoutManager(Context context) {
        super(context);
    }

    public SmoothLinearLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
    }

    @Override
    public void smoothScrollToPosition(RecyclerView recyclerView, RecyclerView.State state, int position) {
        LinearSmoothScroller linearSmoothScroller =
                new LinearSmoothScroller(recyclerView.getContext()) {
                    protected float calculateSpeedPerPixel(DisplayMetrics displayMetrics) {
                        return 0.2f;
                    }
                };
        linearSmoothScroller.setTargetPosition(position);
        startSmoothScroll(linearSmoothScroller);
    }

}

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package com.example.bs.Home;

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.PagerSnapHelper;
import android.support.v7.widget.RecyclerView;

import com.example.bs.R;

import java.util.ArrayList;
import java.util.List;
import java.util.concurrent.Executors;
import java.util.concurrent.ScheduledExecutorService;
import java.util.concurrent.TimeUnit;

public class hom extends AppCompatActivity {
    private List<Integer> list = new ArrayList<>(4);

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.fragment_home);

        list.add(R.drawable.b1);
        list.add(R.drawable.b2);
        list.add(R.drawable.b3);
        list.add(R.drawable.b4);


        BannerAdapter adapter = new BannerAdapter(this, list);
        final RecyclerView recyclerView = findViewById(R.id.recycler);
        final SmoothLinearLayoutManager layoutManager = new SmoothLinearLayoutManager(this, LinearLayoutManager.HORIZONTAL, false);
        recyclerView.setLayoutManager(layoutManager);
        recyclerView.setHasFixedSize(true);
        recyclerView.setAdapter(adapter);
        recyclerView.scrollToPosition(list.size() * 10);

        PagerSnapHelper snapHelper = new PagerSnapHelper();
        snapHelper.attachToRecyclerView(recyclerView);


        final BannerIndicator bannerIndicator = findViewById(R.id.indicator);
        bannerIndicator.setNumber(list.size());

        recyclerView.addOnScrollListener(new RecyclerView.OnScrollListener() {
            @Override
            public void onScrollStateChanged(RecyclerView recyclerView, int newState) {
                if (newState == RecyclerView.SCROLL_STATE_IDLE) {
                    int i = layoutManager.findFirstVisibleItemPosition() % list.size();
                    bannerIndicator.setPosition(i);
                }
            }
        });

        ScheduledExecutorService scheduledExecutorService = Executors.newScheduledThreadPool(1);
        scheduledExecutorService.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                recyclerView.smoothScrollToPosition(layoutManager.findFirstVisibleItemPosition() + 1);
            }
        }, 2000, 2000, TimeUnit.MILLISECONDS);

    }
}