找不到符号类 ActionBarActivity

Question

使用 android studio 4.2.1 一个 java 代码不起作用。 表明 C:\Users\NahidOnim\AndroidStudioProjects\JustJava\app\src\main\java\com\example\android\justjava\MainActivity.java:4： 错误：找不到符号 导入 android.support.v7.app.ActionBarActivity; ^ 符号：类 ActionBarActivity 位置：包 android.support.v7.app

代码如下

package com.example.android.justjava;

import android.os.Bundle;
import android.support.v7.app.ActionBarActivity;
import android.view.View;
import android.widget.TextView;

/**
 * This app displays an order form to order coffee.
 */
public class MainActivity extends ActionBarActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
    }

    /**
     * This method is called when the order button is clicked.
     */
    public void submitOrder(View view) {
        display(1);
    }

    /**
     * This method displays the given quantity value on the screen.
     */
    private void display(int number) {
        TextView quantityTextView = (TextView) findViewById(
                R.id.quantity_text_view);
        quantityTextView.setText("" + number);
    }
}

谁能告诉我为什么会这样？？