找不到符号“Context”，android.content.Context

Question

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();
    }
}

我试图在命令行'$ ant build‘上使用ant编译它，但我一直收到以下错误：

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

有什么建议吗？谢谢!

Answer 1

简短的回答:添加这个

import android.content.Context;

Answer 2

活动中的上下文可以通过YourActivity.this获取，或者使用以下命令更容易

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();
    }
}