找不到符號“上下文”，android.content.Context

Question

我有以下代碼：

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();
    }
}

我正在嘗試在命令行“ $ ant build”上使用ant對其進行編譯，但我不斷收到以下錯誤：

error: cannot find symbol
[javac]         Context context = getApplicationContext();
[javac]         ^

有什么建議嗎？ 謝謝！

Answer 1

活動中的上下文由YourActivity.this或this來獲得

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 = this; // or ActivityNotification.this
        CharSequence text = "Hello toast!";
        int duration = Toast.LENGTH_SHORT;

        Toast toast = Toast.makeText(this, text, duration);
        toast.show();
    }
}

Answer 2

簡短答案：添加此

import android.content.Context;