我的Andriod的HelloWorld----最简单的播放MP3的Demo

白天听了高焕堂老师的Android课程。 晚上完成作业，我的第一个Android程序---最简单的播放MP3的Demo
HelloWorld.java

package com.example.android.wondershare;
import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.LinearLayout;
import android.content.Intent;

import com.example.android.wondershare.SecondActivity;

public class HelloWorld extends Activity implements OnClickListener
{

/** Called when the activity is first created. */
//@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);

LinearLayout layout = new LinearLayout(this);
Button btnPlay = new Button(this);
Button btnExit = new Button(this);
btnPlay.setText("Play");
btnExit.setText("exit");
btnPlay.setId(R.id.play);
btnExit.setId(R.id.exit);
btnPlay.setOnClickListener(this);
btnExit.setOnClickListener(this);

layout.addView(btnPlay);
layout.addView(btnExit);
setContentView(layout);
}

//@Override
public void onClick(View v){
switch (v.getId()) {
case R.id.play:
play();
break;
case R.id.exit:

finish();
break;
}

}

public void play() {
//Jump to Page 2
Intent intent = new Intent();
intent.setClass(HelloWorld.this, SecondActivity.class);
HelloWorld.this.startActivity(intent);

}
public void exit() {

this.finish();
}

}

SecondActivity.java
package com.example.android.wondershare;

import android.app.Activity;

import android.media.MediaPlayer;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.view.View.OnClickListener;

public class SecondActivity extends Activity
//implements OnClickListener
{
private MediaPlayer mPlayer = null;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.second);
//Play ,TBD...
if(mPlayer != null) return;

mPlayer = MediaPlayer.create(this, R.raw.nice);
try {
//mPlayer.prepare();
mPlayer.start();
} catch (Exception e) {
Log.e("StartPlay", "error: " + e.getMessage(), e);
}

}

public void OnStop(View view) {
//Stop Play,TBD...
if (mPlayer != null) {

mPlayer.stop();
mPlayer.release();
mPlayer = null;
}

this.finish();
}

}

second.xml
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent">

<Button
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="@string/stop"
android:onClick="OnStop"
/>

</LinearLayout>

说明：
HelloWorld.java为第一个界面，Play和exit两个button,点击Play进入第二个界面；界面控件代码显示new出来；
SecondActivity.java为第二个界面，进入界面同时播放MP3--dreamed.mp3;点击stop停止播放，并返回第一个界面；界面控件由second.xml控制。