Gallery学习————检测手机中是否存在外部存储设备

　　/**
* 检测外部存储设备
*
* @param requireWriteAccess
* @return
*/
public static boolean hasStorage(boolean requireWriteAccess) {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
if (requireWriteAccess) {
boolean writable = checkFsWritable();
return writable;
} else {
return true;
}
} else if (!requireWriteAccess
&& Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) {
return true;
}
return false;
}

private static boolean checkFsWritable() {
// Create a temporary file to see whether a volume is really writeable.
// It's important not to put it in the root directory which may have a
// limit on the number of files.
String directoryName = Environment.getExternalStorageDirectory()
.toString() + "/DCIM";
File directory = new File(directoryName);
if (!directory.isDirectory()) {
if (!directory.mkdirs()) {
return false;
}
}
File f = new File(directoryName, ".probe");
try {
// Remove stale file if any
if (f.exists()) {
f.delete();
}
if (!f.createNewFile()) {
return false;
}
f.delete();
return true;
} catch (IOException ex) {
return false;
}
}