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Android Bundle

A Bundle is a data structure that provides mapping from String values to Parceable types.

Bundle class definition

Bundle belongs to android.os package.

package android.os;

Bundle is a final class so you cannot derive from it:
public final class Bundle...{}

It derives from a android.os.BaseBundle class:
public final class Bundle extends BaseBundle..{}

Bundle implements two interfaces:

Interface Description
Cloneable So that it supports cloning.
Parcelable So that it supports writing to and restoration from a parcel.

Creating a Bundle

A Bundle is like all Java classes is an Object. Objects do have constructors.

A constructor is a method that gets called when the object is created. When an object is instantiated. Basically the constructors create or construct objects.

Well the Bundle class has 5 of these constructors that we can use to create a Bundle object. They only differ in the parameters we pass to the object.

Constructor Description
Bundle() This will create a new empty Bundle object
Bundle(int capacity) Create a new Bundle object with the total capacity specified in the parameter.
Bundle(Bundle b) Creates a bundle object with a copy of entries from the passed Bundle.
Bundle(PersitableBundle b) This will create a Bundle with a copy of entires from the passed PersistableBundle.

 

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  1. Android BaseBundle

    A BaseBundle is a class that provides mapping from String values to various data types in android.

    This ability to map simple strings to many more data types, some of them complex, is dear to us especially when we want to transfer data among components like activities.

    BaseBundle is a rather new class since it was added in android API level 1.

    This class provides the basis for other Bundle classes. These classes derive from it:

    Class Description
    Bundle Maps Strings to Parcelable types.
    PersistableBundle Maps Strings to various types that can be saved and later restored for use.

    The BaseBundle class is a concrete class and contains several methods for manipulating the data in the Bundle. In fact the other classes do derive some of these methods.

    Let’s have a look at some of these (public) methods we can use to manipulate a BaseBundle:

    ===

    Adding Simple Types to BaseBundle

    There are put... methods for easily inserting data of various types into a basebundle:

    Method Description
    void putString(String key,String value) This will insert a string value into the String replacing any existing value for the passed key.
    void putInt(String key, int value) This will insert an int value into the Bunlde mapping replacing any existing value for the passed key..
    void putLong(String key, long value) This will insert a long value into the Bunlde mapping replacing any existing value for the passed key..
    void putDouble(String key, double value) This will insert a double value into the Bunlde mapping replacing any existing value for the passed key..
    void putBoolean(String key, boolean value) This will insert a double value into the Bunlde mapping replacing any existing value for the passed key..

    Adding Arrays into a BaseBundle

    There are built-in methods for adding arrays of simple types into a BaseBundle as well:

    Method Description
    void putStringArray(String key,String[] value) This will insert an array of strings into the Bundle replacing any existing value for the passed key.
    void putIntArray(String key,int[] value) This will insert an array of integers into the Bundle replacing any existing value for the passed key.
    void putDoubleArray(String key,double[] value) This will insert an array of doubles into the Bundle replacing any existing value for the passed key.
    void putBooleanArray(String key,boolean[] value) This will insert an array of booleans into the Bundle replacing any existing value for the passed key.
    void putLongArray(String key,long[] value) This will insert an array of longs into the Bundle replacing any existing value for the passed key.

    Checking For Existing Items in a BaseBundle

    First you may want to check for emptiness in a Bundle:

    Method Description
    bolean isEmpty() Will check if the Bundle mapping is empty, if so it returns true. If its is not empty it returns false.

    Then you may want to check if the Bundle has a given key:

    Method Description
    boolean containsKey(String key) Will check if the Bundle mapping has the passed key, if so it returns true. If it doesn’t have the key it returns false.

    Getting the Size of a Bundle

    We can know the number of mappings contained in a Bundle as well.

    Method Description
    int size() This will return the number of mappings contained in this Bundle.

    Retrieving Simple Types from a BaseBundle

    If you inserted items into a Bundle, then probably you’ll want to retrieve those items.

    This is easy as the framework provides us with methods to retrieve bundle items. All we need is pass in the key of the bundle.

    Method Description
    String getString(String key) This will return a string value mappped from passed the key.Or null if no mapping with this key exists.
    int getInt(String key,int defaultValue) This will return an int value mappped from the passed key.Or defaultvalue if no mapping with this key exists.
    int getInt(String key) This will return an int value mappped from the passed key.Or 0 if no mapping with this key exists.
    long getLong(String key,long defaultValue) This will return a long value mappped from the passed key.Or defaultValue if no mapping with this key exists.
    long getLong(String key) This will return a long value mappped from the passed key.Or 0L if no mapping with this key exists.
    double getDouble(String key,double defaultValue) This will return a double value mappped from the passed key.Or defaultValue if no mapping with this key exists.
    double getDouble(String key) This will return a double value mappped from the passed key.Or 0.0 if no mapping with this key exists.
    boolean getBoolean(String key,boolean defaultValue) This will return a boolean value mappped from the passed key.Or defaultValue if no mapping with this key exists.
    boolean getBoolean(String key) This will return a boolean value mappped from the passed key.Or false if no mapping with this key exists.

    Retrieving Arrays and Objects From a BaseBundle

    We saw how to pass relatively complex types like arrays and objects.

    Well they are equally easy to retrieve from a bundle:

    Method Description
    Object get(String key) This will return an object entry mappped from passed the key.

    Then the arrays as well:

    Method Description
    String[] getStringArray(String key) This will return an array of strings mappped from passed the key.Or null if no mapping with this key exists.
    int[] getIntArray(String key) This will return an array of ints mappped from passed the key.Or null if no mapping with this key exists.
    long[] getLongArray(String key) This will return an array of longs mappped from passed the key.Or null if no mapping with this key exists.

    Retrieving Keys from a BaseBundle

    The mappings in our Bundle will have unique keys.

    We can then retrieve those keys and hold them in a Set data structure:

    Method Description
    Set keySet() This will return a Set of strings used as keys.

    Removing a given item from a BaseBundle

    We’ve seen how to add and read items from a Bundle.

    Well we can also remove items

    Method Description
    void remove(String key) This will remove an entry with the specified key.

    Clearing a BaseBundle

    A BaseBundle instance can be cleared as well. This removes all entries from the Bundle instance.

    Method Description
    void clear() This will remove all entries from the bundle.

     

  2. Adv
  3. Android PersistableBundle

    A PersistableBundle is a type of Bundle that maps Strings to types types that can be saved and later restored.

    PersistableBundle definition

    PersistableBundle, like Bundle resides in the android.os package:

    package android.os;

    It was added back in android API level 21.

    Persistable class is a final class:

    public final class PersistableBundle..{}

    so you cannot derive from it.

    Like the Bundle class it derives from BaseBundle:

    public final class PersistableBundle extends BaseBundle..{}

    So it inherits a whole bunch of methods for inserting, retrieving, removing entries into the PersistableBundle.

    PersistableBundle implements two interfaces:

    Interface Description
    Cloneable So that it supports cloning.
    Parcelable So that it supports writing to and restoration from a parcel.



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