2. Parcel

可以通过IBinder传递的信息的容器（包括数据和对象引用）。一个Parcel对象可以在一个线程中打包对象，在另一个线程中解开并获取到这些数据。也可以是一个IBinder对象的引用。

Container for a message (data and object references) that can be sent through an IBinder. A Parcel can contain both flattened data that will be unflattened on the other side of the IPC (using the various methods here for writing specific types, or the general Parcelable interface), and references to live IBinder objects that will result in the other side receiving a proxy IBinder connected with the original IBinder in the Parcel.

Parcel不是出于一般目的的序列化机制。这个类是为了提高线程间通信效率而设计的。所以，将Parcel持久化保存不是一个合适的做法。

Parcel is not a general-purpose serialization mechanism. This class (and the corresponding Parcelable API for placing arbitrary objects into a Parcel) is designed as a high-performance IPC transport. As such, it is not appropriate to place any Parcel data in to persistent storage: changes in the underlying implementation of any of the data in the Parcel can render older data unreadable.

Public Methods
final void	appendFrom(Parcel parcel, int offset, int length)
final IBinder[]	createBinderArray()
final ArrayList<IBinder>	createBinderArrayList() Read and return a new ArrayList containing IBinder objects from the parcel that was written with writeBinderList(List) at the current dataPosition().
final boolean[]	createBooleanArray()
final byte[]	createByteArray() Read and return a byte[] object from the parcel.
final char[]	createCharArray()
final double[]	createDoubleArray()
final float[]	createFloatArray()
final int[]	createIntArray()
final long[]	createLongArray()
final String[]	createStringArray()
final ArrayList<String>	createStringArrayList() Read and return a new ArrayList containing String objects from the parcel that was written with writeStringList(List) at the current dataPosition().
final <T> T[]	createTypedArray(Creator<T> c) Read and return a new array containing a particular object type from the parcel at the current dataPosition().
final <T> ArrayList<T>	createTypedArrayList(Creator<T> c) Read and return a new ArrayList containing a particular object type from the parcel that was written with writeTypedList(List) at the current dataPosition().
final int	dataAvail() Returns the amount of data remaining to be read from the parcel.
final int	dataCapacity() Returns the total amount of space in the parcel.
final int	dataPosition() Returns the current position in the parcel data.
final int	dataSize() Returns the total amount of data contained in the parcel.
final void	enforceInterface(String interfaceName)
final boolean	hasFileDescriptors() Report whether the parcel contains any marshalled file descriptors.
final byte[]	marshall() Returns the raw bytes of the parcel.
static Parcel	obtain() Retrieve a new Parcel object from the pool.
final Object[]	readArray(ClassLoader loader) Read and return a new Object array from the parcel at the current dataPosition().
final ArrayList	readArrayList(ClassLoader loader) Read and return a new ArrayList object from the parcel at the current dataPosition().
final void	readBinderArray(IBinder[] val)
final void	readBinderList(List<IBinder> list) Read into the given List items IBinder objects that were written with writeBinderList(List) at the current dataPosition().
final void	readBooleanArray(boolean[] val)
final Bundle	readBundle(ClassLoader loader) Read and return a new Bundle object from the parcel at the current dataPosition(), using the given class loader to initialize the class loader of the Bundle for later retrieval of Parcelable objects.
final Bundle	readBundle() Read and return a new Bundle object from the parcel at the current dataPosition().
final byte	readByte() Read a byte value from the parcel at the current dataPosition().
final void	readByteArray(byte[] val) Read a byte[] object from the parcel and copy it into the given byte array.
final void	readCharArray(char[] val)
final double	readDouble() Read a double precision floating point value from the parcel at the current dataPosition().
final void	readDoubleArray(double[] val)
final void	readException(int code, String msg) Throw an exception with the given message.
final void	readException() Special function for reading an exception result from the header of a parcel, to be used after receiving the result of a transaction.
final ParcelFileDescriptor	readFileDescriptor() Read a FileDescriptor from the parcel at the current dataPosition().
final float	readFloat() Read a floating point value from the parcel at the current dataPosition().
final void	readFloatArray(float[] val)
final HashMap	readHashMap(ClassLoader loader) Please use readBundle(ClassLoader) instead (whose data must have been written with writeBundle(Bundle).
final int	readInt() Read an integer value from the parcel at the current dataPosition().
final void	readIntArray(int[] val)
final void	readList(List outVal, ClassLoader loader) Read into an existing List object from the parcel at the current dataPosition(), using the given class loader to load any enclosed Parcelables.
final long	readLong() Read a long integer value from the parcel at the current dataPosition().
final void	readLongArray(long[] val)
final void	readMap(Map outVal, ClassLoader loader) Please use readBundle(ClassLoader) instead (whose data must have been written with writeBundle(Bundle).
final <T extends Parcelable> T	readParcelable(ClassLoader loader) Read and return a new Parcelable from the parcel.
final Parcelable[]	readParcelableArray(ClassLoader loader) Read and return a new Parcelable array from the parcel.
final PersistableBundle	readPersistableBundle(ClassLoader loader) Read and return a new Bundle object from the parcel at the current dataPosition(), using the given class loader to initialize the class loader of the Bundle for later retrieval of Parcelable objects.
final PersistableBundle	readPersistableBundle() Read and return a new Bundle object from the parcel at the current dataPosition().
final Serializable	readSerializable() Read and return a new Serializable object from the parcel.
final Size	readSize() Read a Size from the parcel at the current dataPosition().
final SizeF	readSizeF() Read a SizeF from the parcel at the current dataPosition().
final SparseArray	readSparseArray(ClassLoader loader) Read and return a new SparseArray object from the parcel at the current dataPosition().
final SparseBooleanArray	readSparseBooleanArray() Read and return a new SparseBooleanArray object from the parcel at the current dataPosition().
final String	readString() Read a string value from the parcel at the current dataPosition().
final void	readStringArray(String[] val)
final void	readStringList(List<String> list) Read into the given List items String objects that were written with writeStringList(List) at the current dataPosition().
final IBinder	readStrongBinder() Read an object from the parcel at the current dataPosition().
final <T> void	readTypedArray(T[] val, Creator<T> c)
final <T> void	readTypedList(List<T> list, Creator<T> c) Read into the given List items containing a particular object type that were written with writeTypedList(List) at the current dataPosition().
final Object	readValue(ClassLoader loader) Read a typed object from a parcel.
final void	recycle() Put a Parcel object back into the pool.
final void	setDataCapacity(int size) Change the capacity (current available space) of the parcel.
final void	setDataPosition(int pos) Move the current read/write position in the parcel.
final void	setDataSize(int size) Change the amount of data in the parcel.
final void	unmarshall(byte[] data, int offest, int length) Set the bytes in data to be the raw bytes of this Parcel.
final void	writeArray(Object[] val) Flatten an Object array into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeBinderArray(IBinder[] val)
final void	writeBinderList(List<IBinder> val) Flatten a List containing IBinder objects into the parcel, at the current dataPosition() and growing dataCapacity() if needed.
final void	writeBooleanArray(boolean[] val)
final void	writeBundle(Bundle val) Flatten a Bundle into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeByte(byte val) Write a byte value into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeByteArray(byte[] b, int offset, int len) Write a byte array into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeByteArray(byte[] b) Write a byte array into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeCharArray(char[] val)
final void	writeDouble(double val) Write a double precision floating point value into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeDoubleArray(double[] val)
final void	writeException(Exception e) Special function for writing an exception result at the header of a parcel, to be used when returning an exception from a transaction.
final void	writeFileDescriptor(FileDescriptor val) Write a FileDescriptor into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeFloat(float val) Write a floating point value into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeFloatArray(float[] val)
final void	writeInt(int val) Write an integer value into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeIntArray(int[] val)
final void	writeInterfaceToken(String interfaceName) Store or read an IBinder interface token in the parcel at the current dataPosition().
final void	writeList(List val) Flatten a List into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeLong(long val) Write a long integer value into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeLongArray(long[] val)
final void	writeMap(Map val) Please use writeBundle(Bundle) instead.
final void	writeNoException() Special function for writing information at the front of the Parcel indicating that no exception occurred.
final void	writeParcelable(Parcelable p, int parcelableFlags) Flatten the name of the class of the Parcelable and its contents into the parcel.
final <T extends Parcelable> void	writeParcelableArray(T[] value, int parcelableFlags) Write a heterogeneous array of Parcelable objects into the Parcel.
final void	writePersistableBundle(PersistableBundle val) Flatten a PersistableBundle into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeSerializable(Serializable s) Write a generic serializable object in to a Parcel.
final void	writeSize(Size val) Flatten a Size into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeSizeF(SizeF val) Flatten a SizeF into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeSparseArray(SparseArray<Object> val) Flatten a generic SparseArray into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeSparseBooleanArray(SparseBooleanArray val)
final void	writeString(String val) Write a string value into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeStringArray(String[] val)
final void	writeStringList(List<String> val) Flatten a List containing String objects into the parcel, at the current dataPosition() and growing dataCapacity() if needed.
final void	writeStrongBinder(IBinder val) Write an object into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final void	writeStrongInterface(IInterface val) Write an object into the parcel at the current dataPosition(), growing dataCapacity() if needed.
final <T extends Parcelable> void	writeTypedArray(T[] val, int parcelableFlags) Flatten a heterogeneous array containing a particular object type into the parcel, at the current dataPosition() and growing dataCapacity() if needed.
final <T extends Parcelable> void	writeTypedList(List<T> val) Flatten a List containing a particular object type into the parcel, at the current dataPosition() and growing dataCapacity() if needed.
final void	writeValue(Object v) Flatten a generic object in to a parcel.