dagger2 use summary: 0 . @ inject identification method (typically constructors), called by dagger2. 1 . @ Inject member variables identified, it indicates that the variable is automatically initialized by dagger2. 2 .interface represents dagger2 need to implement the interface, the role is instantiated @inject member variables. 3 . When the @ Component (modules) specified dagger2 implement the interface, which @Module auxiliary module needs. 4 . @ Provides method identified by the method according to dagger2 automatic matching and call return value. . 5 . The method that realizes @ BindInstance body directly return return parameters, no other processing.