The Ruger SR22 pistol is also hammer-fired, not striker fired. Unlike the M&P22, its hammer is exposed, not enclosed within the slide.

The M&P centerfire pistols are NOT, in any way, shape, or form, a double-action (DA) pistol. Single-action (SA) triggers perform only one function - to drop the hammer/striker. Double-action triggers both cock and fire the hammer/striker. Unless your striker-fired pistol has "second-strike" capability it is not double-action.

Too much confusion has been put out there because most striker-fired pistols either partially or fully cock the striker when cycled. The partially cocked versions are erroneously called double action since the trigger pull finishes cocking the striker. However, since these pistols cannot be fired once the striker has been dropped without cycling the slide, they are in no way double action.