Considering not only reducing the energy consumption based on the fixed energy source but also capturing new energy by RF energy harvesting (EH) for Internet-of-Things (IoT) devices, an integrated energy-efficient strategy for IoT devices is proposed in this article. On the one hand, a node sampling scheduling algorithm based on matrix completion is designed. All the sampling data are handled as matrix elements. The basic idea is to reduce the sampling data and then reconstruct the complete data set with the technology of matrix completion by using the spatial-temporal correlation of all the sampling data. Thus, the IoT nodes can keep dormant more instead of working on data sampling. The energy consumption can be significantly reduced with very little data loss. On the other hand, an adaptive RF energy management strategy is introduced. Based on the self-designed data and energy integrated network (DEIN) system, both data and energy are transferred between the DEIN gateway (DEING) and the DEIN Node (DEINN). With the adaptive energy management strategy, they both automatically switch between the wireless information transfer (WIT) mode and the wireless energy transfer (WET) mode. Combining energy saving with EH, the energy efficiency can be greatly enhanced. The proposed integrated solution aims to decrease the energy consumption of IoT devices and provide them with constant new energy by RF EH. Thus, their battery lives can be prolonged. Both the effectiveness and the efficiency of the proposed integrated strategy have been validated with the simulation.