Binder

See also:

• IBinder

Binder

public Binder ()

Default constructor just initializes the object.

If you're creating a Binder token (a Binder object without an attached interface), you should use Binder(java.lang.String) instead.

Binder

public Binder (String descriptor)

Constructor for creating a raw Binder object (token) along with a descriptor.

The descriptor of binder objects usually specifies the interface they are implementing. In case of binder tokens, no interface is implemented, and the descriptor can be used as a sort of tag to help identify the binder token. This will help identify remote references to these objects more easily when debugging.

attachInterface

public void attachInterface (IInterface owner, 
                String descriptor)

Convenience method for associating a specific interface with the Binder. After calling, queryLocalInterface() will be implemented for you to return the given owner IInterface when the corresponding descriptor is requested.

clearCallingIdentity

public static final long clearCallingIdentity ()

Reset the identity of the incoming IPC on the current thread. This can be useful if, while handling an incoming call, you will be calling on interfaces of other objects that may be local to your process and need to do permission checks on the calls coming into them (so they will check the permission of your own local process, and not whatever process originally called you).

clearCallingWorkSource

public static final long clearCallingWorkSource ()

Clears the work source on this thread.

The work source will be propagated for future outgoing binder transactions executed on this thread.

restoreCallingWorkSource(long) must always be called after clearing the worksource.

A typical use case would be

 long token = Binder.clearCallingWorkSource();
 try {
   // Call an API.
 } finally {
   Binder.restoreCallingWorkSource(token);
 }
 

dump

public void dump (FileDescriptor fd, 
                String[] args)

Implemented to call the more convenient version dump(java.io.FileDescriptor, java.io.PrintWriter, java.lang.String[]).

dumpAsync

public void dumpAsync (FileDescriptor fd, 
                String[] args)

Like dump(java.io.FileDescriptor, java.lang.String[]), but ensures the target executes asynchronously.

flushPendingCommands

public static final void flushPendingCommands ()

Flush any Binder commands pending in the current thread to the kernel driver. This can be useful to call before performing an operation that may block for a long time, to ensure that any pending object references have been released in order to prevent the process from holding on to objects longer than it needs to.

getCallingPid

public static final int getCallingPid ()

Return the ID of the process that sent you the current transaction that is being processed. This PID can be used with higher-level system services to determine its identity and check permissions. If the current thread is not currently executing an incoming transaction, then its own PID is returned. Warning: oneway transactions do not receive PID. Even if you expect a transaction to be synchronous, a misbehaving client could send it as a asynchronous call and result in a 0 PID here. Additionally, if there is a race and the calling process dies, the PID may still be 0 for a synchronous call.

getCallingUid

public static final int getCallingUid ()

Return the Linux UID assigned to the process that sent you the current transaction that is being processed. This UID can be used with higher-level system services to determine its identity and check permissions. If the current thread is not currently executing an incoming transaction, then its own UID is returned.

getCallingUidOrThrow

public static final int getCallingUidOrThrow ()

Return the Linux UID assigned to the process that sent the transaction currently being processed.

getCallingUserHandle

public static final UserHandle getCallingUserHandle ()

Return the UserHandle assigned to the process that sent you the current transaction that is being processed. This is the user of the caller. It is distinct from getCallingUid() in that a particular user will have multiple distinct apps running under it each with their own UID. If the current thread is not currently executing an incoming transaction, then its own UserHandle is returned.

getCallingWorkSourceUid

public static final int getCallingWorkSourceUid ()

Returns the work source set by the caller.

Unlike getCallingUid(), this result of this method cannot be trusted. The caller can set the value to whatever they want. Only use this value if you trust the calling UID.

getInterfaceDescriptor

public String getInterfaceDescriptor ()

Default implementation returns an empty interface name.

isBinderAlive

public boolean isBinderAlive ()

Check to see if the process that the binder is in is still alive. Note that if you're calling on a local binder, this always returns true because your process is alive if you're calling it.

joinThreadPool

public static final void joinThreadPool ()

Add the calling thread to the IPC thread pool. This function does not return until the current process is exiting.

linkToDeath

public void linkToDeath (IBinder.DeathRecipient recipient, 
                int flags)

Local implementation is a no-op.

pingBinder

public boolean pingBinder ()

Default implementation always returns true -- if you got here, the object is alive.

queryLocalInterface

public IInterface queryLocalInterface (String descriptor)

Use information supplied to attachInterface() to return the associated IInterface if it matches the requested descriptor.

restoreCallingIdentity

public static final void restoreCallingIdentity (long token)

Restore the identity of the incoming IPC on the current thread back to a previously identity that was returned by clearCallingIdentity().

restoreCallingWorkSource

public static final void restoreCallingWorkSource (long token)

Restores the work source on this thread using a token returned by setCallingWorkSourceUid(int) or clearCallingWorkSource().

A typical use case would be

 long token = Binder.setCallingWorkSourceUid(uid);
 try {
   // Call an API.
 } finally {
   Binder.restoreCallingWorkSource(token);
 }
 

setCallingWorkSourceUid

public static final long setCallingWorkSourceUid (int workSource)

Sets the work source for this thread.

All the following binder calls on this thread will use the provided work source. If this is called during an on-going binder transaction, all the following binder calls will use the work source until the end of the transaction.

The concept of worksource is similar to WorkSource. However, for performance reasons, we only support one UID. This UID represents the original user responsible for the binder calls.

restoreCallingWorkSource(long) must always be called after setting the worksource.

A typical use case would be

 long token = Binder.setCallingWorkSourceUid(uid);
 try {
   // Call an API.
 } finally {
   Binder.restoreCallingWorkSource(token);
 }
 

The work source will be propagated for future outgoing binder transactions executed on this thread.

transact

public final boolean transact (int code, 
                Parcel data, 
                Parcel reply, 
                int flags)

Default implementation rewinds the parcels and calls onTransact. On the remote side, transact calls into the binder to do the IPC.

unlinkToDeath

public boolean unlinkToDeath (IBinder.DeathRecipient recipient, 
                int flags)

Local implementation is a no-op.

dump

protected void dump (FileDescriptor fd, 
                PrintWriter fout, 
                String[] args)

Print the object's state into the given stream.

onTransact

protected boolean onTransact (int code, 
                Parcel data, 
                Parcel reply, 
                int flags)

Default implementation is a stub that returns false. You will want to override this to do the appropriate unmarshalling of transactions.

If you want to call this, call transact().

Implementations that are returning a result should generally use Parcel.writeNoException and Parcel.writeException to propagate exceptions back to the caller.