android 内外置SD卡的研究
最近网站后台监控上传的app崩溃记录，最常见的一条就是获取手机sd卡根目录出现崩溃。所以有查找各方面的资料，以及看android api源码。
方法二
以前的Android(4.1之前的版本)中，SDcard跟路径通过“/sdcard”或者“/mnt/sdcard”来表示存储卡，而在Jelly Bean系统中修改为了“/storage/sdcard0”，以后可能还会有多个SDcard的情况。
目前为了保持和之前代码的兼容，sdcard路径做了link映射。
为了使您的代码更加健壮并且能够兼容以后的Android版本和新的设备，请通过Environment.getExternalStorageDirectory().getPath()来获取sdcard路径。
1、通用的获取语句
Environment.getExternalStorageDirectory().getPath()2、那么内置sd卡是怎样的
public static String getSoftwareStorageDirectory() {
Map sysInfo=System.getenv();
//获取外置的sd卡
String sd_defult = sysInfo.get("SECONDARY_STORAGE");
return sd_defult;
} 调试时候Map
{ANDROID_SOCKET_zygote=9,
SECONDARY_STORAGE=/storage/sdcard1,
ANDROID_STORAGE=/storage, ANDROID_BOOTLOGO=1,
EXTERNAL_STORAGE=/storage/sdcard0,
ANDROID_ASSETS=/system/app,
ASEC_MOUNTPOINT=/mnt/asec,
PATH=/sbin:/vendor/bin:/system/sbin:/system/bin:/system/xbin,
LOOP_MOUNTPOINT=/mnt/obb,
BOOTCLASSPATH=/system/framework/core.jar:/system/framework/core-junit.jar:
/system/framework/bouncycastle.jar:/system/framework/ext.jar:/system/framework/framework.jar:
/system/framework/telephony-common.jar:/system/framework/mms-common.jar:
/system/framework/android.policy.jar:/system/framework/services.jar:
/system/framework/apache-xml.jar:/system/framework/mediatek-common.jar:
/system/framework/mediatek-framework.jar:/system/framework/secondary-framework.jar:
/system/framework/CustomProperties.jar:/system/framework/mediatek-telephony-common.jar:
/system/framework/mediatek-op.jar,
ANDROID_DATA=/data,
ANDROID_PROPERTY_WORKSPACE=8,49664,
ANDROID_ROOT=/system,
LD_LIBRARY_PATH=/vendor/lib:/system/lib}api17源码，部分源码Environment
private static final String ENV_EXTERNAL_STORAGE = "EXTERNAL_STORAGE";
private static final String ENV_EMULATED_STORAGE_SOURCE = "EMULATED_STORAGE_SOURCE";
private static final String ENV_EMULATED_STORAGE_TARGET = "EMULATED_STORAGE_TARGET";
private static final String ENV_MEDIA_STORAGE = "MEDIA_STORAGE"; public UserEnvironment(int userId) {
// See storage config details at http://source.android.com/tech/storage/
String rawExternalStorage = System.getenv(ENV_EXTERNAL_STORAGE);
String rawEmulatedStorageTarget = System.getenv(ENV_EMULATED_STORAGE_TARGET);
String rawMediaStorage = System.getenv(ENV_MEDIA_STORAGE);
if (TextUtils.isEmpty(rawMediaStorage)) {
rawMediaStorage = "/data/media";
}
if (!TextUtils.isEmpty(rawEmulatedStorageTarget)) {
// Device has emulated storage; external storage paths should have
// userId burned into them.
final String rawUserId = Integer.toString(userId);
final File emulatedBase = new File(rawEmulatedStorageTarget);
final File mediaBase = new File(rawMediaStorage);
// /storage/emulated/0
mExternalStorage = buildPath(emulatedBase, rawUserId);
// /data/media/0
mMediaStorage = buildPath(mediaBase, rawUserId);
} else {
// Device has physical external storage; use plain paths.
if (TextUtils.isEmpty(rawExternalStorage)) {
Log.w(TAG, "EXTERNAL_STORAGE undefined; falling back to default");
rawExternalStorage = "/storage/sdcard0";
}
// /storage/sdcard0
mExternalStorage = new File(rawExternalStorage);
// /data/media
mMediaStorage = new File(rawMediaStorage);
}
mExternalStorageAndroidObb = buildPath(mExternalStorage, DIRECTORY_ANDROID, "obb");
mExternalStorageAndroidData = buildPath(mExternalStorage, DIRECTORY_ANDROID, "data");
mExternalStorageAndroidMedia = buildPath(mExternalStorage, DIRECTORY_ANDROID, "media");
}在上面的源码当中String sdcardPath = System.getenv("EXTERNAL_STORAGE"); 获取也是外置sd卡。
可是在源码中也是没有看到String extSdcardPath = System.getenv("SECONDARY_STORAGE"); 。SECONDARY_STORAGE这个变量是没有，我也纳闷，怎么也可以使用。这就有点疑问了。
获取外置sd卡是否存在的源码
/**
* Gets the current state of the primary "external" storage device.
*
* @see #getExternalStorageDirectory()
*/
public static String getExternalStorageState() {
try {
IMountService mountService = IMountService.Stub.asInterface(ServiceManager
.getService("mount"));
final StorageVolume primary = getPrimaryVolume();
return mountService.getVolumeState(primary.getPath());
} catch (RemoteException rex) {
Log.w(TAG, "Failed to read external storage state; assuming REMOVED: " + rex);
return Environment.MEDIA_REMOVED;
}
}
private static StorageVolume getPrimaryVolume() {
if (sPrimaryVolume == null) {
synchronized (sLock) {
if (sPrimaryVolume == null) {
try {
IMountService mountService = IMountService.Stub.asInterface(ServiceManager
.getService("mount"));
final StorageVolume[] volumes = mountService.getVolumeList();
sPrimaryVolume = StorageManager.getPrimaryVolume(volumes);
} catch (Exception e) {
Log.e(TAG, "couldn't talk to MountService", e);
}
}
}
}
return sPrimaryVolume;
} /**
* getExternalStorageState() returns MEDIA_CHECKING if the media is present and being disk-checked
* 要获取SD卡首先要确认SD卡是否装载
* @return
*/
public boolean getExternalStorageState(){
return Environment.getExternalStorageState().equals(Environment.MEDIA_CHECKING);
}
/**
* getExternalStorageState() returns MEDIA_MOUNTED
* if the media is present and mounted at its mount point with read/write access.
* 要获取SD卡是否可以读写
* @return
*/
public boolean getExternalStorageStateMOUNTED(){
return Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED);
}还有一个问题就是，既然外置sd卡不存在时候Environment.getExternalStorageDirectory().getPath()这条语句获取的是内置的sd卡，那么判断是否是内置sd卡的读写呢？
3、网上看到最多获取外置SD卡路径两个方法
方法一
/**
* 获取外置SD卡路径
*
* @return 应该就一条记录或空
*/
public List getExtSDCardPath() {
List lResult = new ArrayList();
try {
Runtime rt = Runtime.getRuntime();
Process proc = rt.exec("mount");
InputStream is = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
BufferedReader br = new BufferedReader(isr);
String line;
//rootfs / rootfs ro,relatime 0 0
while ((line = br.readLine()) != null) {
if (line.contains("extSdCard")) {
String[] arr = line.split(" ");
String path = arr[1];
File file = new File(path);
if (file.isDirectory()) {
lResult.add(path);
}
}
}
isr.close();
} catch (Exception e) {
}
return lResult;
}方法二
//获取外置存储卡的根路径，如果没有外置存储卡，则返回null
public String getExtSDCardPath2() {
String sdcard_path = null;
String sd_default = Environment.getExternalStorageDirectory()
.getAbsolutePath();
if (sd_default.endsWith("/")) {
sd_default = sd_default.substring(0, sd_default.length() - 1);
}
// 得到路径
try {
Runtime runtime = Runtime.getRuntime();
Process proc = runtime.exec("mount");
InputStream is = proc.getInputStream();
InputStreamReader isr = new InputStreamReader(is);
String line;
BufferedReader br = new BufferedReader(isr);
//rootfs / rootfs ro,relatime 0 0
while ((line = br.readLine()) != null) {
if (line.contains("secure"))
continue;
if (line.contains("asec"))
continue;
if (line.contains("fat") && line.contains("/mnt/")) {
String columns[] = line.split(" ");
if (columns != null && columns.length > 1) {
if (sd_default.trim().equals(columns[1].trim())) {
continue;
}
sdcard_path = columns[1];
}
} else if (line.contains("fuse") && line.contains("/mnt/")) {
String columns[] = line.split(" ");
if (columns != null && columns.length > 1) {
if (sd_default.trim().equals(columns[1].trim())) {
continue;
}
sdcard_path = columns[1];
}
}
}
} catch (Exception e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
return sdcard_path;
}根本没有想要的。
manifest权限
最后总结一下
Environment.getExternalStorageDirectory().getPath()是万能的，不管是外置还是内置sd卡都可以获取。
不过app应用来说是需要固定一个路径的。
我现在使用的是
public String getSoftwareStorageDirectory() {
String strDirectory;
Map sysInfo=System.getenv();
String sd_defult = sysInfo.get("SECONDARY_STORAGE");
if (!CheckDirectoryExists(sd_defult))
{
sd_defult = Environment.getExternalStorageDirectory().getPath();
}
return strDirectory;
}
//判断检出目录是否存在
private boolean CheckDirectoryExists(String fileName) {
if (fileName == null || fileName.length()<=0) {
return false;
}
File temFile = new File(fileName);
File[] childFiles = null;
if (temFile != null)
childFiles = temFile.listFiles();
if (childFiles == null) {
return false;
}
//目录是否可以写
File testFile = new File(temFile, "com_testDir");
if (!testFile.exists()) {
if (!testFile.mkdir()) {
return false;
}
testFile.delete();
}
return true;
} 欢迎大家测试，提供不同机子的测试结果，还有不同源码下是怎样的。
因为有不同厂商，或者用户是刷机，所以有很多奇葩的路径也不足为奇。