仿抖音上下滑动播放视频

不少朋友对短视频，上下滑动播放视频效果比较比较感兴趣，今天看看这个案例。

1、效果图：

讲下大概思路，使用Recycleview配合自定义LinearLayoutManager来实现这个功能，这里着重说下自定义LinearLayoutManager的实现可以看到每当下一个item滑入屏幕时，上面的item会继续播放视频，而滑入的item只有当全部进入屏幕才会播放，而且当手指抬起时，当前item会根据滑动的距离相应的自动滑入滑出，针对这种情形，就会想到使用SnapHelper

RecyclerView在24.2.0版本中新增了SnapHelper这个辅助类，用于辅助RecyclerView在滚动结束时将Item对齐到某个位置。特别是列表横向滑动时，很多时候不会让列表滑到任意位置，而是会有一定的规则限制，这时候就可以通过SnapHelper来定义对齐规则了。

SnapHelper是一个抽象类，官方提供了一个LinearSnapHelper的子类，可以让RecyclerView滚动停止时相应的Item停留中间位置。25.1.0版本中官方又提供了一个PagerSnapHelper的子类，可以使RecyclerView像ViewPager一样的效果，一次只能滑一页，而且居中显示，也就是说使用SnapHelper可以帮助RecyclerView滑动完成后进行对齐操作，让item的侧边对齐或者居中对齐,这样实现上下滑动进行视频切换。这里有SnapHelper的详解

2、正式撸代码：1.首先定义一个接口，用来执行item的相关操作

<code>```
public interface OnViewPagerListener {
    /*初始化完成*/
    void onInitComplete();
    /*释放的监听*/
    void onPageRelease(boolean isNext, int position);
    /*选中的监听以及判断是否滑动到底部*/
    void onPageSelected(int position, boolean isBottom);
}
```复制代码/<code>

2.继承LinearLayoutManager ，对滑入滑出的item回调1中接口里面的方法

<code>```
import android.content.Context;
import android.support.annotation.NonNull;
import android.support.v7.widget.LinearLayoutManager;
import android.support.v7.widget.PagerSnapHelper;
import android.support.v7.widget.RecyclerView;
import android.view.View;

public class MyLayoutManager extends LinearLayoutManager implements RecyclerView.OnChildAttachStateChangeListener {
    private int mDrift;//位移，用来判断移动方向
 

    private PagerSnapHelper mPagerSnapHelper;
    private OnViewPagerListener mOnViewPagerListener;

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

    public MyLayoutManager(Context context, int orientation, boolean reverseLayout) {
        super(context, orientation, reverseLayout);
        mPagerSnapHelper = new PagerSnapHelper();
    }

    @Override
    public void onAttachedToWindow(RecyclerView view) {

        view.addOnChildAttachStateChangeListener(this);
        mPagerSnapHelper.attachToRecyclerView(view);
        super.onAttachedToWindow(view);
    }
//当Item添加进来了  调用这个方法

    //
    @Override
    public void onChildViewAttachedToWindow(@NonNull View view) {
//        播放视频操作 即将要播放的是上一个视频 还是下一个视频
        int position = getPosition(view);
        if (0 == position) {
            if (mOnViewPagerListener != null) {
                mOnViewPagerListener.onPageSelected(getPosition(view), false);
            }

        }
    }

    public void setOnViewPagerListener(OnViewPagerListener mOnViewPagerListener) {
        this.mOnViewPagerListener = mOnViewPagerListener;
    }

    @Override
    public void onScrollStateChanged(int state) {
        switch (state) {
            case RecyclerView.SCROLL_STATE_IDLE:
                View view = mPagerSnapHelper.findSnapView(this);
                int position = getPosition(view);
                if (mOnViewPagerListener != null) {
                    mOnViewPagerListener.onPageSelected(position, position == getItemCount() - 1);
 

                }
//                postion  ---回调 ----》播放


                break;
        }
        super.onScrollStateChanged(state);
    }

    @Override
    public void onChildViewDetachedFromWindow(@NonNull View view) {
//暂停播放操作
        if (mDrift >= 0) {
            if (mOnViewPagerListener != null)
                mOnViewPagerListener.onPageRelease(true, getPosition(view));
        } else {
            if (mOnViewPagerListener != null)
                mOnViewPagerListener.onPageRelease(false, getPosition(view));
        }
    }


    @Override
    public int scrollVerticallyBy(int dy, RecyclerView.Recycler recycler, RecyclerView.State state) {
        this.mDrift = dy;
        return super.scrollVerticallyBy(dy, recycler, state);
    }

    @Override
    public boolean canScrollVertically() {
        return true;
    }
}
```复制代码/<code>

3.接下来就是正常使用recycleview了 配合原生VideoView 播放视频,切换时先用一张截图盖住视频，视频渲染成功再隐藏截图，感觉上是无缝切换(这里是原生播放器初始加载视频会黑屏，如果用更高级的播放器可能不会有这个问题)

<code>```
import android.annotation.TargetApi;
import android.content.Context; 

import android.media.MediaPlayer;
import android.net.Uri;
import android.os.Build;
import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;
import android.support.v7.widget.OrientationHelper;
import android.support.v7.widget.RecyclerView;
import android.util.Log;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.RelativeLayout;
import android.widget.VideoView;


public class MainActivity extends AppCompatActivity {
    private static final String TAG = "douyin";
    private RecyclerView mRecyclerView;
    private MyAdapter mAdapter;
    MyLayoutManager2 myLayoutManager;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        initView();
        initListener();
    }

    private void initView() {
        mRecyclerView = findViewById(R.id.recycler);
        myLayoutManager = new MyLayoutManager2(this, OrientationHelper.VERTICAL, false);

        mAdapter = new MyAdapter(this);
        mRecyclerView.setLayoutManager(myLayoutManager);
        mRecyclerView.setAdapter(mAdapter);

    }

    private void initListener() {
        myLayoutManager.setOnViewPagerListener(new OnViewPagerListener() {
            @Override
            public void onInitComplete() {

            }

            @Override
            public void onPageRelease(boolean isNext, int position) {
                Log.e(TAG, "释放位置:" + position + " 下一页:" + isNext); 

                int index = 0;
                if (isNext) {
                    index = 0;
                } else {
                    index = 1;
                }
                releaseVideo(index);
            }

            @Override
            public void onPageSelected(int position, boolean bottom) {
                Log.e(TAG, "选择位置:" + position + " 下一页:" + bottom);

                playVideo(0);
            }
        });
    }

    class MyAdapter extends RecyclerView.Adapter<myadapter.viewholder> {
        private int[] imgs = {R.mipmap.img_video_1, R.mipmap.img_video_2, R.mipmap.img_video_3, R.mipmap.img_video_4, R.mipmap.img_video_5, R.mipmap.img_video_6, R.mipmap.img_video_7, R.mipmap.img_video_8};
        private int[] videos = {R.raw.video_1, R.raw.video_2, R.raw.video_3, R.raw.video_4, R.raw.video_5, R.raw.video_6, R.raw.video_7, R.raw.video_8};
        private int index = 0;
        private Context mContext;

        public MyAdapter(Context context) {
            this.mContext = context;
        }


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

        @Override
        public void onBindViewHolder(ViewHolder holder, int position) {
            holder.img_thumb.setImageResource(imgs[index]);
            holder.videoView.setVideoURI(Uri.parse("android.resource://" + getPackageName() + "/" + videos[index]));
            index++;
            if (index >= 7) {
                index = 0;
            }
        }

        @Override
        public int getItemCount() {
            return 88;
        }
 

        public class ViewHolder extends RecyclerView.ViewHolder {
            ImageView img_thumb;
            VideoView videoView;
            ImageView img_play;
            RelativeLayout rootView;

            public ViewHolder(View itemView) {
                super(itemView);
                img_thumb = itemView.findViewById(R.id.img_thumb);
                videoView = itemView.findViewById(R.id.video_view);
                img_play = itemView.findViewById(R.id.img_play);
                rootView = itemView.findViewById(R.id.root_view);
            }
        }
    }

    private void releaseVideo(int index) {
        View itemView = mRecyclerView.getChildAt(index);
        final VideoView videoView = itemView.findViewById(R.id.video_view);
        final ImageView imgThumb = itemView.findViewById(R.id.img_thumb);
        final ImageView imgPlay = itemView.findViewById(R.id.img_play);
        videoView.stopPlayback();
        imgThumb.animate().alpha(1).start();
        imgPlay.animate().alpha(0f).start();
    }


    @TargetApi(Build.VERSION_CODES.JELLY_BEAN_MR1)
    private void playVideo(int position) {
        View itemView = mRecyclerView.getChildAt(position);
        final FullWindowVideoView videoView = itemView.findViewById(R.id.video_view);
        final ImageView imgPlay = itemView.findViewById(R.id.img_play);
        final ImageView imgThumb = itemView.findViewById(R.id.img_thumb);
        final RelativeLayout rootView = itemView.findViewById(R.id.root_view);
        final MediaPlayer[] mediaPlayer = new MediaPlayer[1];
        videoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {

            }
        });
        videoView.setOnInfoListener(new MediaPlayer.OnInfoListener() {
            @Override
            public boolean onInfo(MediaPlayer mp, int what, int extra) {
                mediaPlayer[0] = mp;
                mp.setLooping(true);
                imgThumb.animate().alpha(0).setDuration(200).start();
                return false;
            }
        }); 


        videoView.start();

        imgPlay.setOnClickListener(new View.OnClickListener() {
            boolean isPlaying = true;

            @Override
            public void onClick(View v) {
                if (videoView.isPlaying()) {
                    imgPlay.animate().alpha(0.7f).start();
                    videoView.pause();
                    isPlaying = false;
                } else {
                    imgPlay.animate().alpha(0f).start();
                    videoView.start();
                    isPlaying = true;
                }
            }
        });
    }

}
```/<myadapter.viewholder>/<code>

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關鍵字: img 滑动 Override