Digital SLR, half-pressing the shutter can keep focus measurement and photometry, so what should I do if I measure one place first and then another? (Mine is Nikon D90)

I know what you mean. You mean that your photometric point and focus point do not coincide. But generally speaking, the focus should be the metering point, because your aperture shutter combination depends on your subject.

Back to your question, in fact, the easiest way to achieve this goal is manual, which is the same for any brand of SLR. First of all, you measure a little light and record the value of the combination of aperture and shutter with P file. Then release the shutter and adjust it to the M position. Enter the combination value of the aperture and shutter just now, then press the shutter to focus on the point that needs to be focused, and then press all the lenses!