Graphics[{PatternFilling[{"Checkerboard", Red}], Rectangle[]}]
U2 = RegionPlot[\[Pi]rYR < \[Pi]rNR && \[Pi]rNR > \[Pi]rYA && \
\[Pi]rNR > \[Pi]rNA && \[Pi]rNR > 0 && P2NR > 0 && P2YR > 0 &&
P1NR > 0 && P1YR > 0 && P1YR > W1YR && P1NR > W1NR && P2YR > W2YR &&
P2NR > W2NR && X1YR > 0 && X2YR > 0 && X1NR > 0 && X2NR > 0, {q,
0, 2}, {\[Eta], 1, 3}, PlotStyle -> Directive[Opacity[0.5], Black],
FrameLabel -> {q, \[Eta]},
BoundaryStyle -> {Black, Thickness[0.0025]},
LabelStyle -> Directive[Black, Bold], PlotPoints -> 100,
PlotLegends -> {"转售合同不分享信息"},
PatternFilling["Checkerboard", ImageScaled[1/10]] ]

你软件版本低没这功能

哦哦哦这样啊，谢谢了