不少朋友對短視頻，上下滑動播放視頻效果比較比較感興趣，今天看看這個案例。
1、效果圖：
講下大概思路，使用Recycleview配合自定義LinearLayoutManager來實現這個功能，這裡著重說下自定義LinearLayoutManager的實現可以看到每當下一個item滑入屏幕時，上面的item會繼續播放視頻，而滑入的item只有當全部進入屏幕才會播放，而且當手指抬起時，當前item會根據滑動的距離相應的自動滑入滑出，針對這種情形，就會想到使用SnapHelper
RecyclerView在24.2.0版本中新增了SnapHelper這個輔助類，用於輔助RecyclerView在滾動結束時將Item對齊到某個位置。特別是列表橫向滑動時，很多時候不會讓列表滑到任意位置，而是會有一定的規則限制，這時候就可以通過SnapHelper來定義對齊規則了。
SnapHelper是一個抽象類，官方提供了一個LinearSnapHelper的子類，可以讓RecyclerView滾動停止時相應的Item停留中間位置。25.1.0版本中官方又提供了一個PagerSnapHelper的子類，可以使RecyclerView像ViewPager一樣的效果，一次只能滑一頁，而且居中顯示，也就是說使用SnapHelper可以幫助RecyclerView滑動完成後進行對齊操作，讓item的側邊對齊或者居中對齊,這樣實現上下滑動進行視頻切換。這裡有SnapHelper的詳解
2、正式擼代碼：
1.首先定義一個接口，用來執行item的相關操作
```
public interface OnViewPagerListener {
/*初始化完成*/
void onInitComplete();
/*釋放的監聽*/
void onPageRelease(boolean isNext, int position);
/*選中的監聽以及判斷是否滑動到底部*/
void onPageSelected(int position, boolean isBottom);
}
```
2.繼承LinearLayoutManager ，對滑入滑出的item回調1中接口裡面的方法
```
public interface OnViewPagerListener {
/*初始化完成*/
void onInitComplete();
/*釋放的監聽*/
void onPageRelease(boolean isNext, int position);
/*選中的監聽以及判斷是否滑動到底部*/
void onPageSelected(int position, boolean isBottom);
}
```
2.繼承LinearLayoutManager ，對滑入滑出的item回調1中接口裡面的方法
```
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，用來判斷移動方向
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);
}
//當Item添加進來了 調用這個方法
//
@Override
public void onChildViewAttachedToWindow(@NonNull View view) {
// 播放視頻操作 即將要播放的是上一個視頻 還是下一個視頻
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 ---回調 ----》播放
break;
}
super.onScrollStateChanged(state);
}
@Override
public void onChildViewDetachedFromWindow(@NonNull View view) {
//暫停播放操作
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;
}
}
```
3.接下來就是正常使用recycleview了 配合原生VideoView 播放視頻,切換時先用一張截圖蓋住視頻，視頻渲染成功再隱藏截圖，感覺上是無縫切換(這裡是原生播放器初始加載視頻會黑屏，如果用更高級的播放器可能不會有這個問題)
```
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, "釋放位置:" + position + " 下一頁:" + isNext);
int index = 0;
if (isNext) {
index = 0;
} else {
index = 1;
}
releaseVideo(index);
}
@Override
public void onPageSelected(int position, boolean bottom) {
Log.e(TAG, "選擇位置:" + position + " 下一頁:" + bottom);
playVideo(0);
}
});
}
class MyAdapter extends RecyclerView.Adapter<myadapter.viewholder> {/<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;
}
}
});
}
}
```
原創作者：龐哈哈哈12138，原文：https://www.jianshu.com/p/3a043cd4eb1f
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