android devices offline

D:\android_code\0708\tools>adb devices
List of devices attached
015d2109f414120e offline
015d2109f414120e device

D:\android_code\0708\tools>adb push Y:\out\target\product\kai\system\framework\framework.jar system/framework
error: device offline

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解决

adb kill-server

adb start-server