添加少量方法时，活动不会显示

Question

我有应该播放视频的项目。当我按下按钮时我的MyVideo活动没有启动，但是当我评论或删除几个方法我的活动开始时。我应该添加任何其他方法来显示活动，或者我应该添加显而易见的东西。

package com.nazad.org;


import android.app.Activity;
import android.net.Uri;
import android.os.Bundle;
import android.widget.MediaController;
import android.widget.VideoView;

public class MyVideo extends Activity {

    String SrcPath = "rtsp://v2.cache1.c.youtube.com/CjYLENy73wIaLQmhulgrtR-1JxMYDSANFEIJbXYtZ29vZ2xlSARSBXdhdGNoYMOcgLDU6ZWTUAw=/0/0/0/video.3gp";

    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.video);
        VideoView myVideoView = (VideoView) findViewById(R.id.myvideoview);


        myVideoView.setScrollContainer(true) ;
        myVideoView.getAnimation().setDetachWallpaper(true);
        myVideoView.setVideoURI(Uri.parse(SrcPath));
        myVideoView.setMediaController(new MediaController(this));
        myVideoView.requestFocus();
        myVideoView.start();
    }
}

这是我的开始活动，有两个按钮：

package com.nazad.org;

import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MyNapredNazadActivity extends Activity implements OnClickListener {
    /** Called when the activity is first created. */

    Button next;
    Button back;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        next = (Button) findViewById(R.id.next);
        back = (Button) findViewById(R.id.back);

        next.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent i = new Intent(MyNapredNazadActivity.this, MyVideo.class);
                i.setClass(MyNapredNazadActivity.this, MyVideo.class);
                MyNapredNazadActivity.this.startActivity(i);
            }
        });

        back.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                // TODO Auto-generated method stub
                Intent ii = new Intent(MyNapredNazadActivity.this,
                        MySimple.class);
                // i.setClass(MyNapredNazadActivity.this, MyVideo.class);
                MyNapredNazadActivity.this.startActivity(ii);
            }
        });

    }

    @Override
    public void onClick(View v) {
        // TODO Auto-generated method stub
        Intent i = new Intent(MyNapredNazadActivity.this, MyVideo.class);
this.startActivity(i);
    }

}

和清单：

<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
    package="com.nazad.org"
    android:versionCode="1"
    android:versionName="1.0" >

    <uses-sdk android:minSdkVersion="8" />

    <application
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name" >
        <activity
            android:name=".MyNapredNazadActivity"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".MyVideo"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
        <activity
            android:name=".MySimple"
            android:label="@string/app_name" >
            <intent-filter>
                <action android:name="android.intent.action.MAIN" />

                <category android:name="android.intent.category.LAUNCHER" />
            </intent-filter>
        </activity>
    </application>

</manifest>