Android 获取SD卡路径:
外置sd卡路径,也许很多同学在平时的工作中并不会用到,因为现在很多机型都不支持外置sd卡(这也是Google目标),所以并不用考虑外置sd卡的路径问题。除了开发文件管理类的应用之外,其他应用使用 Enviroment 这个类中的一些静态方法就能满足需要。但也有一些特殊需求需要用到外置sd卡路径,那怎么才能准确获得外置sd卡的路径呢?
方法一
//内置sd卡路径 String sdcardPath = System.getenv("EXTERNAL_STORAGE"); //内置sd卡路径 String sdcardPath = Environment.getExternalStorageDirectory().getAbsolutePath(); //外置置sd卡路径 String extSdcardPath = System.getenv("SECONDARY_STORAGE"); 在Enviroment类的源码中获得sd卡路径其实也是通过 System.getnv() 方法来实现的,如隐藏的方法: /** {@hide} */ public static File getLegacyExternalStorageDirectory() { return new File(System.getenv(ENV_EXTERNAL_STORAGE)); }
注:更详细的内容还是去看Enviroment源码。
另外要注意的是,在API 23版本中 SECONDARY_STORAGE 被移除。
方法二
private static String getStoragePath(Context mContext, boolean is_removale) { StorageManager mStorageManager = (StorageManager) mContext.getSystemService(Context.STORAGE_SERVICE); Class storageVolumeClazz = null; try { storageVolumeClazz = Class.forName("android.os.storage.StorageVolume"); Method getVolumeList = mStorageManager.getClass().getMethod("getVolumeList"); Method getPath = storageVolumeClazz.getMethod("getPath"); Method isRemovable = storageVolumeClazz.getMethod("isRemovable"); Object result = getVolumeList.invoke(mStorageManager); final int length = Array.getLength(result); for (int i = 0; i < length; i++) { Object storageVolumeElement = Array.get(result, i); String path = (String) getPath.invoke(storageVolumeElement); boolean removable = (Boolean) isRemovable.invoke(storageVolumeElement); if (is_removale == removable) { return path; } } } catch (ClassNotFoundException e) { e.printStackTrace(); } catch (InvocationTargetException e) { e.printStackTrace(); } catch (NoSuchMethodException e) { e.printStackTrace(); } catch (IllegalAccessException e) { e.printStackTrace(); } return null; }
通过反射的方式使用在sdk中被 隐藏 的类 StroageVolume 中的方法getVolumeList(),获取所有的存储空间(Stroage Volume),然后通过参数is_removable控制,来获取内部存储和外部存储(内外sd卡)的路径,参数 is_removable为false时得到的是内置sd卡路径,为true则为外置sd卡路径。
在API 23 Enviroment 类中的内部类 UserEnvironment 中有一方法getExternalDirs与此一样,代码如下:
public File[] getExternalDirs() { final StorageVolume[] volumes = StorageManager.getVolumeList(mUserId,StorageManager.FLAG_FOR_WRITE); final File[] files = new File[volumes.length]; for (int i = 0; i < volumes.length; i++) { files[i] = volumes[i].getPathFile(); } return files; }
再看Enviroment的getExternalStorageDirectory方法实现:
public static File getExternalStorageDirectory() { throwIfUserRequired(); return sCurrentUser.getExternalDirs()[0]; }
可以看出,在API 23时,先是通过getExternalDirs()获取到所有存储空间的File[]数组,这个数组的第一个值:getExternalDirs()[0],即为内置sd卡所在路径。
而在API 23 之前的版本中,并没有类似getExternalDirs()的方法通过StorageVolume直接获得存储空间(Storage Volume),而时通过别的方式来实现的,看关键方法的源码:
public static File getExternalStorageDirectory() { throwIfUserRequired(); return sCurrentUser.getExternalDirsForApp()[0]; }
这里的 getExternalDirsForApp() 和上面的 getExternalDirs() 的作用是一样的,都是得到所有存储空间的File[]数组。
public File[] getExternalDirsForApp() { return mExternalDirsForApp; }
mExternalDirsForApp 是在 Enviroment 类中的内部类 UserEnvironment 的构造方法中初始化的,Enviroment#UserEnvironment构造函数源码如下:
public UserEnvironment(int userId) { // See storage config details at http://source.android.com/tech/storage/ String rawExternalStorage = System.getenv(ENV_EXTERNAL_STORAGE); String rawEmulatedSource = System.getenv(ENV_EMULATED_STORAGE_SOURCE); String rawEmulatedTarget = System.getenv(ENV_EMULATED_STORAGE_TARGET); String rawMediaStorage = System.getenv(ENV_MEDIA_STORAGE); if (TextUtils.isEmpty(rawMediaStorage)) { rawMediaStorage = "/data/media"; } ArrayListexternalForVold = Lists.newArrayList(); ArrayList externalForApp = Lists.newArrayList(); if (!TextUtils.isEmpty(rawEmulatedTarget)) { // Device has emulated storage; external storage paths should have // userId burned into them. final String rawUserId = Integer.toString(userId); final File emulatedSourceBase = new File(rawEmulatedSource); final File emulatedTargetBase = new File(rawEmulatedTarget); final File mediaBase = new File(rawMediaStorage); // /storage/emulated/0 externalForVold.add(buildPath(emulatedSourceBase, rawUserId)); externalForApp.add(buildPath(emulatedTargetBase, rawUserId)); // /data/media/0 mEmulatedDirForDirect = 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 externalForVold.add(new File(rawExternalStorage)); externalForApp.add(new File(rawExternalStorage)); // /data/media mEmulatedDirForDirect = new File(rawMediaStorage); } // Splice in any secondary storage paths, but only for owner final String rawSecondaryStorage = System.getenv(ENV_SECONDARY_STORAGE); if (!TextUtils.isEmpty(rawSecondaryStorage) && userId == UserHandle.USER_OWNER) { for (String secondaryPath : rawSecondaryStorage.split(":")) { externalForVold.add(new File(secondaryPath)); externalForApp.add(new File(secondaryPath)); } } mExternalDirsForVold = externalForVold.toArray(new File[externalForVold.size()]); mExternalDirsForApp = externalForApp.toArray(new File[externalForApp.size()]); }
也可以根据这个方法得到一个获取所有存储空间的路径的方法getStorageDirectories():
/** * Returns all available SD-Cards in the system (include emulated) * * Warning: Hack! Based on Android source code of version 4.3 (API 18) * Because there is no standard way to get it. * TODO: Test on future Android versions 4.4+ * * @return paths to all available SD-Cards in the system (include emulated) */ private static final Pattern DIR_SEPARATOR = Pattern.compile("/"); public ListgetStorageDirectories() { // Final set of paths final ArrayList rv = new ArrayList (); // Primary physical SD-CARD (not emulated) final String rawExternalStorage = System.getenv("EXTERNAL_STORAGE"); // All Secondary SD-CARDs (all exclude primary) separated by ":" final String rawSecondaryStoragesStr = System.getenv("SECONDARY_STORAGE"); // Primary emulated SD-CARD final String rawEmulatedStorageTarget = System.getenv("EMULATED_STORAGE_TARGET"); if (TextUtils.isEmpty(rawEmulatedStorageTarget)) { // Device has physical external storage; use plain paths. if (TextUtils.isEmpty(rawExternalStorage)) { // EXTERNAL_STORAGE undefined; falling back to default. rv.add("/storage/sdcard0"); } else { rv.add(rawExternalStorage); } } else { // Device has emulated storage; external storage paths should have // userId burned into them. final String rawUserId; if (Build.VERSION.SDK_INT < Build.VERSION_CODES.JELLY_BEAN_MR1) { rawUserId = ""; } else { final String path = Environment.getExternalStorageDirectory().getAbsolutePath(); final String[] folders = DIR_SEPARATOR.split(path); final String lastFolder = folders[folders.length - 1]; boolean isDigit = false; try { Integer.valueOf(lastFolder); isDigit = true; } catch (NumberFormatException ignored) { } rawUserId = isDigit ? lastFolder : ""; } // /storage/emulated/0[1,2,...] if (TextUtils.isEmpty(rawUserId)) { rv.add(rawEmulatedStorageTarget); } else { rv.add(rawEmulatedStorageTarget + File.separator + rawUserId); } } // Add all secondary storages if (!TextUtils.isEmpty(rawSecondaryStoragesStr)) { // All Secondary SD-CARDs splited into array final String[] rawSecondaryStorages = rawSecondaryStoragesStr.split(File.pathSeparator); Collections.addAll(rv, rawSecondaryStorages); } rootmode = Sp.getBoolean("rootmode", false); if (rootmode) rv.add("/"); File usb = getUsbDrive(); if (usb != null && !rv.contains(usb.getPath())) rv.add(usb.getPath()); return rv; } public File getUsbDrive() { File parent; parent = new File("/storage"); try { for (File f : parent.listFiles()) { if (f.exists() && f.getName().toLowerCase().contains("usb") && f.canExecute()) { return f; } } } catch (Exception e) { } parent = new File("/mnt/sdcard/usbStorage"); if (parent.exists() && parent.canExecute()) return (parent); parent = new File("/mnt/sdcard/usb_storage"); if (parent.exists() && parent.canExecute()) return parent; return null; }
综上分析,通过方法一和方法二都可以正确的获取内外sd卡路径,但方法一会存在以下问题:
1、API>=23 时方法一无效(暂未测试)
2、有些厂商的Rom改动太多,对相关原生API的支持存在问题,这时方法一可能会存在问题。
3、其他一些情况造成的原因(基本与2差不多,是ROM等因素造成的)
所以,在使用时建议使用方法二来获取内外置sd卡路径,在API 23(Android 6.0)之前使用getStorageDirectories() 应该也是OK的。
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