/**
* Searches the query string for the first value with the given key.
*
* <p><strong>Warning:</strong> Prior to Jelly Bean, this decoded
* the '+' character as '+' rather than ' '.
*
* @param key which will be encoded
* @throws UnsupportedOperationException if this isn't a hierarchical URI
* @throws NullPointerException if key is null
* @return the decoded value or null if no parameter is found
*/
public String getQueryParameter(String key)
在Android中操作Uri经常会调用上述方法，可能自己粗心大意，没注意注释，注释上已经说明，返回值是null或者是解码之后的内容。所以通常不需要自己在对返回值进行解码，否则可能引起二次解码带来的问题。
