我的Apps VideoStream无法播放

Question

我一直在尝试将视频播放器部署到我的应用上，到目前为止我通过YouTube视频完成了这项工作。但从他所做的，他的视频播放完美。无论出于何种原因，我无法让我的视频播放器启动流。我尝试过不同的格式，但似乎都没有。

代码如下：

package com.example.user.tabfinal;

import android.app.ProgressDialog;
import android.media.MediaPlayer;
import android.net.Uri;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.ImageButton;
import android.widget.ImageView;
import android.widget.VideoView;

public class videoActivity extends AppCompatActivity implements 
View.OnClickListener {

ProgressDialog pd ;
VideoView videoView;
ImageButton btnPlay;

String URL = "http://31.210.87.4/film/fullmp4best/Assassin_s_Creed_Official_Trailer_2_2016.mp4";

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main2);

    videoView = (VideoView)findViewById(R.id.videoView);
    btnPlay = (ImageButton)findViewById(R.id.btnPlay);


}

@Override
public void onClick(View v) {
    pd = new ProgressDialog(mainActivity2.this);
    pd.setMessage("Please wait...");
    pd.setCanceledOnTouchOutside(false);
    pd.show();

        try{
            if(!videoView.isPlaying()){
            Uri uri = Uri.parse(URL);
            videoView.setVideoURI(uri);
            videoView.setOnCompletionListener(new MediaPlayer.OnCompletionListener() {
                @Override
                public void onCompletion(MediaPlayer mp) {
                    btnPlay.setImageResource(R.drawable.ic_play);

                }
            });

            }else{
                videoView.pause();
                btnPlay.setImageResource(R.drawable.ic_play);
            }

        }
        catch (Exception Ex){

        }

    videoView.requestFocus();
    videoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
        @Override
        public void onPrepared(MediaPlayer mp) {
            pd.dismiss();
            mp.setLooping(true);
            videoView.start();
            btnPlay.setImageResource(R.drawable.ic_pause);
        }
    });
}
}