1)// 在手机中创建文件

FileOutputStream phone_outStream =this.openFileOutput("1.txt", Context.MODE_PRIVATE);

phone_outStream.write("HELLO".getBytes());

 

FileOutputStream phone_outStream1 =openFileOutput("1.txt", Context.MODE_APPEND); //追加模式继续写

phone_outStream1.write(" world".getBytes());

//读取并显示

byte[] s= new byte[80];

FileInputStream phone_inputStream =openFileInput("1.txt");

phone_inputStream.read(s);    

Toast.makeText(this, new String(s), Toast.LENGTH_SHORT).show();

结论:不管手机data文件夹是否能在DDMS中看到东西, (没有root权限就会空空如也.)程序能够正常运行,并toast出正确内容.

2)如果试图用该方法来写入到手机内部存储中,是不行的:

java.io.FileNotFoundException: /2.txt: open failed: EROFS (Read-only file system)

File f = new File("2.txt");

FileOutputStream fs = new FileOutputStream( f ); //这句导致异常

openFileOutput();是android的api, android.content.ContextWrapper.openFileOutput();

FileOutputStream .是Java的类.  java.io.FileOutputStream

 

此文转自：http://www.cnblogs.com/sinawear/archive/2012/11/26.html

 

 

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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();

    }