android中把文件存储在SD卡中

当我们需要把文件存储在android中的SD卡时，可以用下面的方法：

public void savesd(String filename,String content)throws Exception {
File file = new File(Environment.getExternalStorageDirectory(),filename);
FileOutputStream outStream = new FileOutputStream(file);
write(content,outStream);
}
private void write(String content, FileOutputStream outStream) throws IOException {
outStream.write(content.getBytes());
outStream.close();
}其中filename是文件名称，content 是文件内容。
//通过下面的方法可以找的SD卡的路径

Environment.getExternalStorageDirectory()
//装换成字节流
content.getBytes()调用savesd方法时需要进行状态的判断
（常用：MEDIA_MOUNTED 存储媒体已经挂载，并且挂载点可读/写。MEDIA_MOUNTED_READ_ONLY 存储媒体已经挂载，挂载点只读。）

if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED))清单文件中需要获得下列权限

android.permission.MOUNT_UNMOUNT_FILESYSTEMS
android.permission.WRITE_EXTERNAL_STORAGE