读写sdk文件

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添加相关权限

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

要判断一下是否插入SD卡和是否具有读写的能力：

Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

详细代码如下

读：

/** *  * @param fileName *            文件的名字 * @param content *            文件的内容 * @return */public boolean saveContentToSdCard(String fileName, String content) {boolean flag = false;FileOutputStream fileOutputStream = null;// sdcard所在的路径File file = new File(Environment.getExternalStorageDirectory(), fileName);//if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {try {// true 写入的内容可追加fileOutputStream = new FileOutputStream(file, true);fileOutputStream.write(content.getBytes());fileOutputStream.write("\r\n".getBytes());flag = true;} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {if (fileOutputStream != null) {try {fileOutputStream.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}return flag;}

写：

public String getFileFromSdcard(String fileName) {FileInputStream inputstream = null;// 缓冲区缓存的流，和磁盘无关，不需要关闭ByteArrayOutputStream outputStream = new ByteArrayOutputStream();File file = new File(Environment.getExternalStorageDirectory(), fileName);if (Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)) {try {inputstream = new FileInputStream(file);int len = 0;byte[] data = new byte[1024];while ((len = inputstream.read(data)) != -1) {outputStream.write(data, 0, len);}} catch (FileNotFoundException e) {// TODO Auto-generated catch blocke.printStackTrace();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();} finally {if (inputstream != null) {try {inputstream.close();} catch (IOException e) {// TODO Auto-generated catch blocke.printStackTrace();}}}}return new String(outputStream.toByteArray());}

Environmet类参数介绍

常用常量

String MEDIA_MOUNTED

当前Android的外部存储器可读可写

String MEDIA_MOUNTED_READ_ONLY

当前Android的外部存储器只读

常用方法

方法名称

描述

public static File getDataDirectory ()

获得Android下的data文件夹的目录

public static File getDownloadCacheDirectory ()

获得Android Download/Cache 内容的目录

public static File getExternalStorageDirectory ()

获得Android外部存储器也就是SDCard的目录

public static String getExternalStorageState ()

获得Android外部存储器的当前状态

public static File getRootDirectory ()

获得Android下的root文件夹的目录

总结几个步骤：

1、先判断这台手机设备上是否有SDCard且具有读写SDCard的权限

Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)

2、调用Environment.getExternalStorageDirectory()获得到外部存储器的目录

3、使用IO流对外部存储器进行文件的读写

4、在AndroidMainfest.xml中添加权限

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