Question

公有构造方法	说明
public Bundle()	Constructs a new, empty Bundle
public Bundle(ClassLoader loader)	Constructs a new, empty Bundle that uses a specific ClassLoader for instantiating Parcelable and Serializable objects.
public Bundle(int capacity)	Constructs a new, empty Bundle sized to hold the given number of elements.
public Bundle(Bundle b)	Constructs a Bundle containing a copy of the mappings from the given Bundle.
public Bundle(PersistableBundle b)	Constructs a Bundle containing a copy of the mappings from the given PersistableBundle.

第 5 个构造函数中的 PersistableBundle 也是继承自 BaseBundle 的，Bundle 还提供了一个静态方法，用来返回只包含一个键值对的 Bundle 对象，具体源码如下：

public static Bundle forPair(String key, String value) {
  Bundle b = new Bundle(1);
  b.putString(key, value);
  return b;
}