本小例子讲的是比较麻烦的一种，
[java]
package com.example.closeall;

import java.util.ArrayList;
import java.util.List;

import android.os.Bundle;
import android.app.Activity;
import android.content.Intent;
import android.view.Menu;
import android.view.View;

public class MainActivity extends Activity {
private static List<Activity> activities = new ArrayList<Activity>();
private static int count = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
if(count == 0 ){
setTitle("主窗口");
count++;
}else{
setTitle("窗口"+count);
count++;
}
activities.add(this);
}

public void onClick_ShowNewActivity(View view){
Intent intent = new Intent(this,MainActivity.class);
startActivity(intent);
}

public void onClick_CloseAllActivity(View view){
for(int i = 1; i < activities.size(); i++){
if(activities.get(i) != null){
activities.get(i).finish();
}
}

count = 1;
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}

}
[xml]
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:orientation="vertical" >

<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="显示新窗口" android:onClick="onClick_ShowNewActivity"/>
<Button
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="返回主窗口，并关闭除了主窗口外的所有窗口" android:onClick="onClick_CloseAllActivity" />

</LinearLayout>

[/xml]
[/java]