继承AlertDialog，写一个倒计时的dialog。java语法报错，高手帮忙

[yayayo780503]

frameworks/base/core/java/com/android/internal/app/ShutdownThread.java:207: 不兼容的类型
找到： android.app.AlertDialog
需要： com.android.internal.app.TimerDialog
.create();

我已经在create里面return TimerDialog类型的，为何还是报同样的错。

调用的地方：
private static TimerDialog mTimerDialog;
mTimerDialog = new TimerDialog.Builder(context)
.setTitle(com.android.internal.R.string.power_off)
.setMessage("Seconds")
.create();

类实现代码如下：
public class TimerDialog extends AlertDialog{

private int count;
private AlertDialog myDia = null;

public MYHandler myHandler;

private Context mContext;
private String countmsg = new String();



public TimerDialog(Context ctx){
super(ctx);
mContext = ctx;

}

protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
myHandler = new MYHandler();
myHandler.sendEmptyMessage(count);

}

public void setCount(int cnt)
{
count = cnt;

}



public static class Builder extends AlertDialog.Builder{
private final AlertController.AlertParams P;

public Builder(Context ctx)
{
super(ctx);
}


public TimerDialog create()
{
final TimerDialog dialog = new TimerDialog(P.mContext);
P.apply(dialog.mAlert);
dialog.setCancelable(P.mCancelable);
dialog.setOnCancelListener(P.mOnCancelListener);
if (P.mOnKeyListener != null) {
dialog.setOnKeyListener(P.mOnKeyListener);
}
return dialog;
}

public TimerDialog show() {
TimerDialog dialog = create();
dialog.show();
return dialog;
}

}

[jtbreeze]

请问问题解决了，我也遇到同样的问题了