android - 不显示普通 Android 应用程序中的对话框？

Question

我有以下应用程序。我正在尝试做一件非常简单的事情。只是在启动时显示警报。但它只是显示这条消息

"[2012-04-13 17:38:23 - HelloDriod] ActivityManager: Starting: Intent { act=android.intent.action.MAIN cat=[android.intent.category.LAUNCHER] cmp=hellodriod.hello/.HelloDriodActivity }
[2012-04-13 17:38:23 - HelloDriod] ActivityManager: Warning: Activity not started, its current task has been brought to the front"

在模拟器上我只看到项目名称和空白屏幕。我错过了什么吗？任何指示表示赞赏。

package hellodriod.hello;


import android.app.Activity;
import android.app.AlertDialog;
import android.content.DialogInterface;
import android.os.Bundle;



public class HelloDriodActivity extends Activity {
    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        AlertDialog.Builder builder = new AlertDialog.Builder(this);
        builder.setMessage("Are you sure you want to exit?")
               .setCancelable(false)
               .setPositiveButton("Yes", new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {

                   }
               })
               .setNegativeButton("No", new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                   }
               });
        AlertDialog alert = builder.create();

    }
}

Answer 1

您实际上没有显示对话框。

alert.show();