我是一个初学者，努力让这个工作今天。

下面是我最终选择的类。它起作用了，但我想知道我的解决方案有多不完美。不管怎样，我希望你们中一些更有经验的人可能愿意看看我的IO课程，并给我一些建议。干杯!

public class HighScore {
    File data = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator);
    File file = new File(data, "highscore.txt");
    private int highScore = 0;

    public int readHighScore() {
        try {
            BufferedReader br = new BufferedReader(new FileReader(file));
            try {
                highScore = Integer.parseInt(br.readLine());
                br.close();
            } catch (NumberFormatException | IOException e) {
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            try {
                file.createNewFile();
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
            e.printStackTrace();
        }
        return highScore;
    }

    public void writeHighScore(int highestScore) {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter(file));
            bw.write(String.valueOf(highestScore));
            bw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

我是一个初学者，努力让这个工作今天。

下面是我最终选择的类。它起作用了，但我想知道我的解决方案有多不完美。不管怎样，我希望你们中一些更有经验的人可能愿意看看我的IO课程，并给我一些建议。干杯!

public class HighScore {
    File data = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + File.separator);
    File file = new File(data, "highscore.txt");
    private int highScore = 0;

    public int readHighScore() {
        try {
            BufferedReader br = new BufferedReader(new FileReader(file));
            try {
                highScore = Integer.parseInt(br.readLine());
                br.close();
            } catch (NumberFormatException | IOException e) {
                e.printStackTrace();
            }
        } catch (FileNotFoundException e) {
            try {
                file.createNewFile();
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
            e.printStackTrace();
        }
        return highScore;
    }

    public void writeHighScore(int highestScore) {
        try {
            BufferedWriter bw = new BufferedWriter(new FileWriter(file));
            bw.write(String.valueOf(highestScore));
            bw.close();
        } catch (IOException e) {
            e.printStackTrace();
        }
    }
}

科特林

class FileReadWriteService {

    private var context:Context? = ContextHolder.instance.appContext

    fun writeFileOnInternalStorage(fileKey: String, sBody: String) {
        val file = File(context?.filesDir, "files")
        try {
            if (!file.exists()) {
                file.mkdir()
            }
            val fileToWrite = File(file, fileKey)
            val writer = FileWriter(fileToWrite)
            writer.append(sBody)
            writer.flush()
            writer.close()
        } catch (e: Exception) {
            Logger.e(classTag, e)
        }
    }

    fun readFileOnInternalStorage(fileKey: String): String {
        val file = File(context?.filesDir, "files")
        var ret = ""
        try {
            if (!file.exists()) {
                return ret
            }
            val fileToRead = File(file, fileKey)
            val reader = FileReader(fileToRead)
            ret = reader.readText()
            reader.close()
        } catch (e: Exception) {
            Logger.e(classTag, e)
        }
        return ret
    }
}

对于那些寻找读取和写入字符串到文件的一般策略的人:

首先，获取一个文件对象

您需要存储路径。对于内部存储，使用:

File path = context.getFilesDir();

外置存储(SD卡)使用:

File path = context.getExternalFilesDir(null);

然后创建你的文件对象:

File file = new File(path, "my-file-name.txt");

写入一个字符串到文件中

FileOutputStream stream = new FileOutputStream(file);
try {
    stream.write("text-to-write".getBytes());
} finally {
    stream.close();
}

或者用谷歌番石榴

字符串内容=文件。toString(文件、StandardCharsets.UTF_8);

将文件读入字符串

int length = (int) file.length();

byte[] bytes = new byte[length];

FileInputStream in = new FileInputStream(file);
try {
    in.read(bytes);
} finally {
    in.close();
}

String contents = new String(bytes);   

或者如果你用谷歌番石榴

String contents = Files.toString(file,"UTF-8");

为了完整起见，我要提一下

String contents = new Scanner(file).useDelimiter("\\A").next();

它不需要库，但基准测试比其他选项慢50% - 400%(在我的Nexus 5上的各种测试中)。

笔记

对于这些策略，您将被要求捕获IOException。

Android上默认的字符编码是UTF-8。

如果你使用外部存储，你需要添加到你的清单:

<uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE"/>

or

<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE"/>

写权限意味着读权限，所以不需要两者兼备。

public static void writeStringAsFile(final String fileContents, String fileName) {
    Context context = App.instance.getApplicationContext();
    try {
        FileWriter out = new FileWriter(new File(context.getFilesDir(), fileName));
        out.write(fileContents);
        out.close();
    } catch (IOException e) {
        Logger.logError(TAG, e);
    }
}

public static String readFileAsString(String fileName) {
    Context context = App.instance.getApplicationContext();
    StringBuilder stringBuilder = new StringBuilder();
    String line;
    BufferedReader in = null;

    try {
        in = new BufferedReader(new FileReader(new File(context.getFilesDir(), fileName)));
        while ((line = in.readLine()) != null) stringBuilder.append(line);

    } catch (FileNotFoundException e) {
        Logger.logError(TAG, e);
    } catch (IOException e) {
        Logger.logError(TAG, e);
    } 

    return stringBuilder.toString();
}

Kotlin的方法是在文件上使用内置的扩展函数

写:yourFile.writeText (textFromEditText) 读:yourFile.readText ()