Question

所以我试图从文本文件addToLibrary.txt中读取以下字符串

 file:/Users/JEAcomputer/Music/iTunes/iTunes%20Media/Music/Flight%20Of%20The%20Conchords/Flight%20Of%20The%20Conchords/06%20Mutha'uckas.mp3

但是当我这样做时，我得到以下错误：

java.io.FileNotFoundException: file:/Users/JEAcomputer/Music/iTunes/iTunes%20Media/Music/Flight%20Of%20The%20Conchords/Flight%20Of%20The%20Conchords/06%20Mutha'uckas.mp3 (No such file or directory)

奇怪的是我使用这种方法从fileChooser获得了该字符串：

public static void addToLibrary(File f) {

    String fileName = "addToLibrary.txt";

    try {
        FileWriter filewriter = new FileWriter(fileName, true);
        BufferedWriter bufferedWriter = new BufferedWriter(filewriter);
        bufferedWriter.newLine();
        bufferedWriter.write(f.toURI().toString());
        System.out.println("Your file has been written");
        bufferedWriter.close();
    } catch (IOException ex) {
        System.out.println(
            "Error writing to file '"
            + fileName + "'");
    } finally {
    }
}

更奇怪的错误是我的文件阅读器可以读取另一个文件夹中的内容，但不能读取iTunes Media中的任何内容。我尝试使用以下方法读取不同文件夹中的所有文件：

public void getMusicDirectory() {
    int index = 0;
    try {


        File[] contents = musicDir.listFiles();
        //System.out.println(contents[3].toString());
        for (int i = 0; i < contents.length; i++) {
            //System.out.println("----------------------------------------"+contents.length);
            String name = contents[i].getName();
            //System.out.println(name);

            if (name.indexOf(".mp3") == -1) {
                continue;
            }

            FileInputStream file = new FileInputStream(contents[i]);
            file.read();
            System.out.println(contents[i].toURI().toString());
            songsDir.add(new Song((new MediaPlayer(new Media(contents[i].toURI().toString()))), contents[i]));
            file.close();
        }
    } catch (Exception e) {
        System.out.println("Error -- " + e.toString());
    }
    try(BufferedReader br = new BufferedReader(new FileReader("addToLibrary.txt"))) {

        //System.out.println("In check login try");
        for (String line; (line = br.readLine()) != null; ) {
            FileInputStream file = new FileInputStream(new File(line));
            file.read();
            songsDir.add(new Song(new MediaPlayer(new Media(line)), new File(line)));
            file.close();
        }
        // line is not visible here.
    } catch (Exception e) {
        System.out.println("Error reading add to library-- " + e.toString());
    }


}

那么我怎样才能做到这一点？为什么方法的第一部分有效但不是第二部分？

Answer 1

阅读字符串

时没有问题

file:/Users/JEAcomputer/Music/iTunes/iTunes%20Media/Music/Flight%20Of%20The%20Conchords/Flight%20Of%20The%20Conchords/06%20Mutha'uckas.mp3

来自文件。那部分工作正常。您的问题是在此之后，当您尝试使用路径打开文件时：

file:/Users/JEAcomputer/Music/iTunes/iTunes%20Media/Music/Flight%20Of%20The%20Conchords/Flight%20Of%20The%20Conchords/06%20Mutha'uckas.mp3

因为那不是一条路径;它是一个URI（尽管它可以转换为路径）。

你可以将其转换为路径，以便打开它，但你没有理由 - 你的代码实际上没有从文件中读取（除了第一个字节，它没有做任何事情）因此没有必要打开它。删除以下行：

FileInputStream file = new FileInputStream(contents[i]); // THIS ONE
file.read(); // THIS ONE
System.out.println(contents[i].toURI().toString());
songsDir.add(new Song((new MediaPlayer(new Media(contents[i].toURI().toString()))), contents[i]));
file.close(); // THIS ONE

和

FileInputStream file = new FileInputStream(new File(line)); // THIS ONE
file.read(); // THIS ONE
songsDir.add(new Song(new MediaPlayer(new Media(line)), new File(line)));
file.close(); // THIS ONE

Answer 2

file:/Users/JEAcomputer/Music/iTunes/iTunes%20Media/Music/Flight%20Of%20The%20Conchords/Flight%20Of%20The%20Conchords/06%20Mutha'uckas.mp3不是有效的File引用，尤其是在Windows下。

由于您已将String标识为URI，因此您应该将其视为......

URI uri = URI.create("file:/Users/JEAcomputer/Music/iTunes/iTunes%20Media/Music/Flight%20Of%20The%20Conchords/Flight%20Of%20The%20Conchords/06%20Mutha'uckas.mp3");

好的，但是，没有真正的方法可以阅读URI，但您可以阅读URL，因此我们需要将URI转换为URL幸运的是，这很简单......

URL url = uri.toURL();

从那里你可以使用URL#openStream打开InputStream（你可以将其包裹在InputStreamReader中）并阅读文件的内容，例如......

String imageFile = "file:/...";
URI uri = URI.create(imageFile);
try {
    URL url = uri.toURL();
    try (InputStream is = url.openStream()) {

        byte[] bytes = new byte[1024 * 4];
        int bytesRead = -1;
        int totalBytesRead = 0;
        while ((bytesRead = is.read(bytes)) != -1) {

            // Somthing, something, something, bytes
            totalBytesRead += bytesRead;

        }

        System.out.println("Read a total of " + totalBytesRead);

    } catch (IOException ex) {
        ex.printStackTrace();
    }
} catch (MalformedURLException ex) {
    ex.printStackTrace();
}

但是，您可以为自己保存很多问题并停止使用f.toURI().toString());（File#toURI#toString）之类的内容，而只需使用File#getPath代替......这样您就可以从File ...

创建新的String引用

此外，您的资源管理需要一些工作，基本上，如果您打开它，您应该关闭它。有关更多提示，请参阅The try-with-resources Statement

读取文件java.io时出错

2 个答案: