Another idea for android controls:

 

This second version (bottom one) is just a bit different:

• There are 2 virtual sticks
• One for walking / running, depending of how far from center stick is player will walk or run in the stick direction
• One for shooting / fast shooting, depending of how far from center stick is player will shoot or quick shoot in the stick direction
• Removed the walk / run buttons
• Shoot / quick shoot buttons remain as they can be used when lock is enabled (they will not be visible otherwise)
• Shoot stick ignores current locked target, it will not unlock it nor will it shoot in its direction (buttons must be used)

This second version is a bit better I think, but maybe I’ll just put both versions.

This second version might also suit controller mode for PC, in controller mode lock will be available through a button to cycle through targets. But as my controller has a problem on the main axis, I will not be able to develop controller support for now.