【Android】数据存储之SDcard

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SD卡有时候可能因为用户将其挂载在PC上，或者设为只读，或者没有插入SD卡，所以使用SD卡存储数据之前必须检测SD卡是否可用。

1.在清单文件中加入：

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

这样为我们读写SD卡提供了权限。

2.获取SD卡的状态使用：

Environment.getExternalStorageState()

所以检测是否可以写的语句为：

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

所以往SD卡读取文件的代码如下：

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

写入文件代码如下：

public boolean saveContentToSdcard(String filename, String content) {boolean flag = false;FileOutputStream fileOutputStream = null;// 获得sdcrad所在的路径File file = new File(Environment.getExternalStorageDirectory(),filename);// 判断sdcard是否可用if (Environment.MEDIA_MOUNTED.equals(Environment.getExternalStorageState())) {try {fileOutputStream = new FileOutputStream(file);fileOutputStream.write(content.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;}