直接上代码~

注意权限

<!--手机存储-->
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

1.写入数据

    private void writeData() {
        String filePath = "/sdcard/Gyt/";
        String fileName = "data.txt";
        writeTxtToFile("Wx:lcti1314", filePath, fileName);
    }

// 将字符串写入到文本文件中
    private void writeTxtToFile(String strcontent, String filePath, String fileName) {
        //生成文件夹之后，再生成文件，不然会出错
        makeFilePath(filePath, fileName);

        String strFilePath = filePath + fileName;
        // 每次写入时，都换行写
        String strContent = strcontent + "\r\n";
        try {
            File file = new File(strFilePath);
            if (!file.exists()) {
                Log.d("TestFile", "Create the file:" + strFilePath);
                file.getParentFile().mkdirs();
                file.createNewFile();
            }
            RandomAccessFile raf = new RandomAccessFile(file, "rwd");
            raf.seek(file.length());
            raf.write(strContent.getBytes());
            raf.close();
        } catch (Exception e) {
            Log.e("TestFile", "Error on write File:" + e);
        }
    }

//生成文件

  private File makeFilePath(String filePath, String fileName) {
        File file = null;
        makeRootDirectory(filePath);
        try {
            file = new File(filePath + fileName);
            if (!file.exists()) {
                file.createNewFile();
            }
        } catch (Exception e) {
            e.printStackTrace();
        }
        return file;
    }

//生成文件夹

    private static void makeRootDirectory(String filePath) {
        File file = null;
        try {
            file = new File(filePath);
            if (!file.exists()) {
                file.mkdir();
            }
        } catch (Exception e) {
            Log.i("error:", e + "");
        }
    }

2.读取数据

//读取指定目录下的所有TXT文件的文件内容
    private String getFileContent(File file) {
        String content = "";
        if (!file.isDirectory()) {  //检查此路径名的文件是否是一个目录(文件夹)
            if (file.getName().endsWith("txt")) {//文件格式为""文件
                try {
                    InputStream instream = new FileInputStream(file);
                    if (instream != null) {
                        InputStreamReader inputreader
                                = new InputStreamReader(instream, "UTF-8");
                        BufferedReader buffreader = new BufferedReader(inputreader);
                        String line = "";
                        //分行读取
                        while ((line = buffreader.readLine()) != null) {
                            content += line + "\n";
                        }
                        instream.close();//关闭输入流
                    }
                } catch (java.io.FileNotFoundException e) {
                    Log.d("TestFile", "The File doesn't not exist.");
                } catch (IOException e) {
                    Log.d("TestFile", e.getMessage());
                }
            }
        }
        return content;
    }

3.代码调用

代码调用.png

2.效果展示

效果展示.gif