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StorageVolume

public final class StorageVolume
extends Object implements Parcelable

java.lang.Object
   ↳ android.os.storage.StorageVolume


Information about a shared/external storage volume for a specific user.

A device always has one (and one only) primary storage volume, but it could have extra volumes, like SD cards and USB drives. This object represents the logical view of a storage volume for a specific user: different users might have different views for the same physical volume (for example, if the volume is a built-in emulated storage).

The storage volume is not necessarily mounted, applications should use getState() to verify its state.

Applications willing to read or write to this storage volume needs to get a permission from the user first, which can be achieved in the following ways:

  • To get access to standard directories (like the DIRECTORY_PICTURES), they can use the createAccessIntent(String). This is the recommend way, since it provides a simpler API and narrows the access to the given directory (and its descendants).
  • To get access to any directory (and its descendants), they can use the Storage Acess Framework APIs (such as ACTION_OPEN_DOCUMENT and ACTION_OPEN_DOCUMENT_TREE, although these APIs do not guarantee the user will select this specific volume.
  • To get read and write access to the primary storage volume, applications can declare the READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE permissions respectively, with the latter including the former. This approach is discouraged, since users may be hesitant to grant broad access to all files contained on a storage device.

It can be obtained through getStorageVolumes() and getPrimaryStorageVolume() and also as an extra in some broadcasts (see EXTRA_STORAGE_VOLUME).

See getExternalStorageDirectory() for more info about shared/external storage semantics.

Summary

Constants

String EXTRA_STORAGE_VOLUME

Name of the Parcelable extra in the ACTION_MEDIA_REMOVED, ACTION_MEDIA_UNMOUNTED, ACTION_MEDIA_CHECKING, ACTION_MEDIA_NOFS, ACTION_MEDIA_MOUNTED, ACTION_MEDIA_SHARED, ACTION_MEDIA_BAD_REMOVAL, ACTION_MEDIA_UNMOUNTABLE, and ACTION_MEDIA_EJECT broadcast that contains a StorageVolume.

Inherited constants

From interface android.os.Parcelable

Fields

public static final Creator<StorageVolume> CREATOR

Public methods

Intent createAccessIntent(String directoryName)

Builds an intent to give access to a standard storage directory or entire volume after obtaining the user's approval.

int describeContents()

Describe the kinds of special objects contained in this Parcelable instance's marshaled representation.

boolean equals(Object obj)

Indicates whether some other object is "equal to" this one.

String getDescription(Context context)

Returns a user-visible description of the volume.

String getState()

Returns the current state of the volume.

String getUuid()

Gets the volume UUID, if any.

int hashCode()

Returns a hash code value for the object.

boolean isEmulated()

Returns true if the volume is emulated.

boolean isPrimary()

Returns true if the volume is the primary shared/external storage, which is the volume backed by getExternalStorageDirectory().

boolean isRemovable()

Returns true if the volume is removable.

String toString()

Returns a string representation of the object.

void writeToParcel(Parcel parcel, int flags)

Flatten this object in to a Parcel.

Inherited methods

From class java.lang.Object
From interface android.os.Parcelable

Constants

EXTRA_STORAGE_VOLUME

added in API level 24
String EXTRA_STORAGE_VOLUME

Name of the Parcelable extra in the ACTION_MEDIA_REMOVED, ACTION_MEDIA_UNMOUNTED, ACTION_MEDIA_CHECKING, ACTION_MEDIA_NOFS, ACTION_MEDIA_MOUNTED, ACTION_MEDIA_SHARED, ACTION_MEDIA_BAD_REMOVAL, ACTION_MEDIA_UNMOUNTABLE, and ACTION_MEDIA_EJECT broadcast that contains a StorageVolume.

Constant Value: "android.os.storage.extra.STORAGE_VOLUME"

Fields

CREATOR

added in API level 24
Creator<StorageVolume> CREATOR

Public methods

createAccessIntent

added in API level 24
Intent createAccessIntent (String directoryName)

Builds an intent to give access to a standard storage directory or entire volume after obtaining the user's approval.

When invoked, the system will ask the user to grant access to the requested directory (and its descendants). The result of the request will be returned to the activity through the onActivityResult method.

To gain access to descendants (child, grandchild, etc) documents, use buildDocumentUriUsingTree(Uri, String), or buildChildDocumentsUriUsingTree(Uri, String) with the returned URI.

If your application only needs to store internal data, consider using Context.getExternalFilesDirs, getExternalCacheDirs(), or getExternalMediaDirs(), which require no permissions to read or write.

Access to the entire volume is only available for non-primary volumes (for the primary volume, apps can use the READ_EXTERNAL_STORAGE and WRITE_EXTERNAL_STORAGE permissions) and should be used with caution, since users are more likely to deny access when asked for entire volume access rather than specific directories.

Parameters
directoryName String: must be one of DIRECTORY_MUSIC, DIRECTORY_PODCASTS, DIRECTORY_RINGTONES, DIRECTORY_ALARMS, DIRECTORY_NOTIFICATIONS, DIRECTORY_PICTURES, DIRECTORY_MOVIES, DIRECTORY_DOWNLOADS, DIRECTORY_DCIM, or DIRECTORY_DOCUMENTS, or null to request access to the entire volume.
Returns
Intent intent to request access, or null if the requested directory is invalid for that volume.

See also:

describeContents

added in API level 24
int describeContents ()

Describe the kinds of special objects contained in this Parcelable instance's marshaled representation. For example, if the object will include a file descriptor in the output of writeToParcel(Parcel, int), the return value of this method must include the CONTENTS_FILE_DESCRIPTOR bit.

Returns
int a bitmask indicating the set of special object types marshaled by this Parcelable object instance.

equals

added in API level 24
boolean equals (Object obj)

Indicates whether some other object is "equal to" this one.

The equals method implements an equivalence relation on non-null object references:

  • It is reflexive: for any non-null reference value x, x.equals(x) should return true.
  • It is symmetric: for any non-null reference values x and y, x.equals(y) should return true if and only if y.equals(x) returns true.
  • It is transitive: for any non-null reference values x, y, and z, if x.equals(y) returns true and y.equals(z) returns true, then x.equals(z) should return true.
  • It is consistent: for any non-null reference values x and y, multiple invocations of x.equals(y) consistently return true or consistently return false, provided no information used in equals comparisons on the objects is modified.
  • For any non-null reference value x, x.equals(null) should return false.

The equals method for class Object implements the most discriminating possible equivalence relation on objects; that is, for any non-null reference values x and y, this method returns true if and only if x and y refer to the same object (x == y has the value true).

Note that it is generally necessary to override the hashCode method whenever this method is overridden, so as to maintain the general contract for the hashCode method, which states that equal objects must have equal hash codes.

Parameters
obj Object: the reference object with which to compare.
Returns
boolean true if this object is the same as the obj argument; false otherwise.

getDescription

added in API level 24
String getDescription (Context context)

Returns a user-visible description of the volume.

Parameters
context Context
Returns
String the volume description

getUuid

added in API level 24
String getUuid ()

Gets the volume UUID, if any.

Returns
String

hashCode

added in API level 24
int hashCode ()

Returns a hash code value for the object. This method is supported for the benefit of hash tables such as those provided by HashMap.

The general contract of hashCode is:

  • Whenever it is invoked on the same object more than once during an execution of a Java application, the hashCode method must consistently return the same integer, provided no information used in equals comparisons on the object is modified. This integer need not remain consistent from one execution of an application to another execution of the same application.
  • If two objects are equal according to the equals(Object) method, then calling the hashCode method on each of the two objects must produce the same integer result.
  • It is not required that if two objects are unequal according to the equals(java.lang.Object) method, then calling the hashCode method on each of the two objects must produce distinct integer results. However, the programmer should be aware that producing distinct integer results for unequal objects may improve the performance of hash tables.

As much as is reasonably practical, the hashCode method defined by class Object does return distinct integers for distinct objects. (This is typically implemented by converting the internal address of the object into an integer, but this implementation technique is not required by the Java™ programming language.)

Returns
int a hash code value for this object.

isEmulated

added in API level 24
boolean isEmulated ()

Returns true if the volume is emulated.

Returns
boolean is removable

isPrimary

added in API level 24
boolean isPrimary ()

Returns true if the volume is the primary shared/external storage, which is the volume backed by getExternalStorageDirectory().

Returns
boolean

isRemovable

added in API level 24
boolean isRemovable ()

Returns true if the volume is removable.

Returns
boolean is removable

toString

added in API level 24
String toString ()

Returns a string representation of the object. In general, the toString method returns a string that "textually represents" this object. The result should be a concise but informative representation that is easy for a person to read. It is recommended that all subclasses override this method.

The toString method for class Object returns a string consisting of the name of the class of which the object is an instance, the at-sign character `@', and the unsigned hexadecimal representation of the hash code of the object. In other words, this method returns a string equal to the value of:

 getClass().getName() + '@' + Integer.toHexString(hashCode())
 

Returns
String a string representation of the object.

writeToParcel

added in API level 24
void writeToParcel (Parcel parcel, 
                int flags)

Flatten this object in to a Parcel.

Parameters
parcel Parcel: The Parcel in which the object should be written.
flags int: Additional flags about how the object should be written. May be 0 or PARCELABLE_WRITE_RETURN_VALUE.
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