Almost all operations on a QJniObject require a QJniEnvironment,
including the construction and destruction of a QJniObject. Instead of
instantiating a temporary QJniEnvironment object in each call, store the
one from the constructor in the private, and reuse it.
Pass the stored environment through to other functions needing it, and
add a checkAndClearExceptions() wrapper.
Static class members still need their own QJniEnvironment, but we can
reuse the one we have to get both jclass and jmethodID rather than
creating new QJniEnvironments in several wrappers.
As a drive-by, clean up nullptr usage in the test that failed when
shortcutting isSameObject for the trivial cases.
Change-Id: Ibadbd2be8a0ec9ab62daf285608ee7fe0a3c8852
Reviewed-by: Assam Boudjelthia <assam.boudjelthia@qt.io>
944200b5a9