Question

我正在创建一个MP3播放器。它要求用户输入歌曲名称等。但是我一直收到错误说：

PlaylistDriver.java:108: error: cannot find symbol
  FileInputStream file = new FileInputStream("C:\\Users\\KThi\\Music\\" + name + ".mp3");

symbol:   variable name
location: class PlaylistDriver.playMusicListener
1 error

变量“name”已在以下声明：

 public static void addSong() 
   {//Add Song 

      Scanner keyboard = new Scanner(System.in);
      System.out.print("Enter song name: ");
      String name = keyboard.nextLine(); <----------- Variable "name" declared

这是完整的代码：

import java.util.Scanner;
import javax.swing.JButton;
import javax.swing.JFrame;
import java.awt.event.ActionListener;
import java.awt.*;
import java.io.*;   
import java.awt.event.*;
import java.io.FileInputStream;
import java.io.BufferedInputStream;
import javazoom.jl.player.advanced.AdvancedPlayer;  

public class PlaylistDriver 
{//Start of class
   public static Playlist list;
   private AdvancedPlayer player;

   public static void main(String[] args) throws Exception
   {//Start of main
      list = new Playlist();
      new PlaylistDriver().SETUP();

      while(true) 
      {
         menu();
         processInput();
      }

   }

   public void SETUP()
   {
      JFrame frame = new JFrame("MP3 PLAYER");
      frame.setSize(200, 100);
      frame.setDefaultCloseOperation(JFrame.EXIT_ON_CLOSE);
      JButton btnplay = new JButton("Play");
      JButton btnstop = new JButton("Stop");
      btnplay.addActionListener(new playMusicListener());
      btnstop.addActionListener(new stopMusicListener());
      frame.getContentPane().add(BorderLayout.WEST, btnplay);
      frame.getContentPane().add(BorderLayout.EAST, btnstop);      
      frame.setVisible(true);
   }

   public static void processInput()
   {//Start of Process Input
      Scanner keyboard = new Scanner(System.in);
      String input = keyboard.nextLine().toLowerCase();
      switch(input.charAt(0)) 
      {//Start of switch
         case 'a':
            addSong();
            break;
         case 'i':
            printSongByIndex(); 
            break;      
         case 'n':
            removeSongByName();
            break;
         case 'p':
            printSongs();
            break;
         case 's':
            getSize();
            break;
         case 't':
            getTotalTime();
            break;
         case 'f':
            getFormattedTime();
            break;
         case 'c':
            clearSongs();
            break;   
         case 'q':
            System.exit(0);
            break;
         default:
            System.out.println("...........");
      }//End of switch
   }//End of Process Input
   public static void addSong() 
   {//Add Song 

      Scanner keyboard = new Scanner(System.in);
      System.out.print("Enter song name: ");
      String name = keyboard.nextLine();
      System.out.print("Please enter song artist: ");
      String artist = keyboard.nextLine();      
      System.out.print("Please enter an album: ");
      String album = keyboard.nextLine();
      System.out.print("Please enter genre: ");
      String genre = keyboard.nextLine();
      System.out.print("Please enter length of song: ");
      double length = keyboard.nextDouble();

      Song information = new Song(name, artist, album, length, genre);
      list.add(information);

   }//End of Add Song

   public class playMusicListener implements ActionListener
   {

      public void actionPerformed(ActionEvent a)
      {
         try
         {
            FileInputStream file = new FileInputStream("C:\\Users\\KThi\\Music\\" + name + ".mp3");
            player = new AdvancedPlayer(file);
            player.play();
         }  

         catch(Exception e)
         {
            System.out.println(e);
         }
      }
   }

   public class stopMusicListener implements ActionListener
   {
      public void actionPerformed(ActionEvent a)
      {
         try
         {
            FileInputStream file = new FileInputStream("");  
            player = new AdvancedPlayer(file);
            player.stop();
         }
         catch(Exception ex)
         {
            System.out.println(ex);
         }
      }
   }



   public static void printSongs()  
   {//Print Song Information 
      System.out.println(list);
   }//End of Print Song Information

   public static void printSongByIndex() 
   {//Print all songs
      System.out.println("Please enter index of song to view: ");
      Scanner keyboard = new Scanner(System.in);
      int information = keyboard.nextInt();
      System.out.print(list.get(information));  
   }

   public static void removeSongByName() 
   {//To remove song
      System.out.print("\nPlease enter the name of the song to remove: ");
      Scanner keyboard = new Scanner(System.in);
      String name = keyboard.nextLine();
      list.remove( name );
   }//End of remove song

   public static void getSize() 
   {//Get size of song
      System.out.println("\nTotal number of songs: " + list.size());
   }

   public static void getTotalTime()  
   {//Get Total Time
      System.out.println("Total Time: " + list.totalTime());
   }

   public static void getFormattedTime()
   {//Get formatted time
      System.out.println("Total Formatted Time:" + list.formattedTotalTime());
   }

   public static void clearSongs() 
   {//Clear Songs
      list.clear();
   }

   public static void menu() 
   {//Print Menu
      System.out.println("--------MP3 PLAYLIST--------");
      System.out.println("[A]dd a Song");
      System.out.println("[P]rint songs");
      System.out.println("Pr[i]nt song by index");
      System.out.println("Remove song by [n]ame");
      System.out.println("Get total [s]ize");
      System.out.println("Get total [t]ime");
      System.out.println("Get [f]ormatted time");
      System.out.println("[C]lear all songs");
      System.out.println("[Q]uit");
   }
}//End of class

Answer 1

变量名称在类 PlaylistDriver 中定义，但不在 playMusicListener 中定义。

这里的错误原因是你没有在playMusicListener中定义变量名，这反过来会导致错误

btnplay.addActionListener（new playMusicListener（））;.

因此，根据您的要求，您需要定义一种方法来指定按下播放按钮时要播放的歌曲。

无法创建MP3播放器

1 个答案: