Java 如何在TabActivity中添加OnBackPressed？

有谁能告诉我如何在TabActivity中添加后退按钮按下方法的侦听器吗？
这是我的密码。在何处添加backbutton pressed方法

HomeActivity.java

public class HomeActivity extends TabActivity {
public static TabHost tabHost;
public static TabSpec hometab,extrastab,coursetab,logintab;
 @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.home_tab_layout);

        tabHost = getTabHost();

        hometab = tabHost.newTabSpec("Home");
        hometab.setIndicator("", getResources().getDrawable(R.drawable.home_tab));
        hometab.setContent(new Intent().setClass(this,HomeTabActivity.class));

        coursetab = tabHost.newTabSpec("Courses");        
        coursetab.setIndicator("", getResources().getDrawable(R.drawable.courses_tab));
        coursetab.setContent(new Intent(this,MainActivity.class));

        logintab = tabHost.newTabSpec("Login");
        logintab.setIndicator("", getResources().getDrawable(R.drawable.login_tab));
        logintab.setContent(new Intent(this,LoginTabActivity.class));

        extrastab = tabHost.newTabSpec("Extras");
        extrastab.setIndicator("", getResources().getDrawable(R.drawable.extras_tab));
        extrastab.setContent(new Intent(this,ExtrasTabActivity.class));

        tabHost.addTab(hometab); 
        tabHost.addTab(coursetab); 
        tabHost.addTab(logintab); 
        tabHost.addTab(extrastab);

        tabHost.setPadding(5, 5, 5, 5);
    }
}

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在Activity类中编写onBackPressed（）方法如何？ 就像：

public class Tab extends TabActivity {

    @Override
    public void onBackPressed() {
        super.onBackPressed();
    }

}

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详细说明你的问题。。。