Android 布局未显示在选项卡主机中

我在我的应用程序中使用了TabHost。我按照教程来实现它。它工作正常，但单击选项卡时未显示指定的布局。这是代码。请帮忙

public class HelpScreen extends TabActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.inst_manual);

        TabHost host = getTabHost();

        TabSpec btnHelp = host.newTabSpec("Buttons Help");
        btnHelp.setIndicator("Buttons Help",getResources().getDrawable(R.drawable.brushes_help));
        Intent buttonsHelp = new Intent(HelpScreen.this, ButtonsHelp.class);
        btnHelp.setContent(buttonsHelp);

        TabSpec drawHelp = host.newTabSpec("Drawing Help");
        drawHelp.setIndicator("Drawing Help",getResources().getDrawable(R.drawable.brushes_help));
        Intent drawingHelp = new Intent(HelpScreen.this, DrawingHelp.class);
        drawHelp.setContent(drawingHelp);

        host.addTab(btnHelp);
        host.addTab(drawHelp);
    }
}

public class ButtonsHelp extends Activity {

@Override
protected void onCreate(Bundle savedInstanceState) {
    // TODO Auto-generated method stub
    super.onCreate(savedInstanceState);
    setContentView(R.layout.buttons_help);
} }

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试着创造这样的意图

Intent buttonsHelp = new Intent().setClass(this, ButtonsHelp.class);
Intent drawingHelp = new Intent().setClass(this, DrawingHelp.class);

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这很奇怪，它对我有用。单击另一个按钮时发生了什么？我的意思是显示什么布局？按钮单击btnHelp.setonclicklistenernewview.OnClickListener{@Override public void onClickView v{Intent i=new Intentthis，HelpScreen.class；startActivityi；}；剩下的代码也有问题。