android.content.context 找不到,找不到符号“上下文”，android.content.Context

我有以下代码：

package com.androidtest.notification;

import android.app.Activity;

import android.os.Bundle;

import android.widget;

import android.widget.Toast;

import android.content.Context;

public class activityNotification extends Activity

{

@Override

public void onCreate(Bundle savedInstanceState)

{

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

Context context = getApplicationContext();

CharSequence text = "Hello toast!";

int duration = Toast.LENGTH_SHORT;

Toast toast = Toast.makeText(context, text, duration);

toast.show();

}

}

我正在尝试在命令行“ $ ant build”上使用ant对其进行编译，但我不断收到以下错误：

error: cannot find symbol

[javac] Context context = getApplicationContext();

[javac] ^

有什么建议吗？谢谢！