手机连着电脑，并且打开的调试工具，
运行 cordova run android 结果打包成功，但手机的页面却无法显示页面，为什么？

BUILD SUCCESSFUL in 2s

47 actionable tasks: 1 executed, 46 up-to-date
Built the following apk(s):

    E:\qns-mobile\platforms\android\app\build\outputs\apk\debug\app-debug.apk

ANDROID_HOME=C:Program FilesAndroidandroid-sdk
JAVA_HOME=C:Program FilesjavaJDKjdk
No target specified, deploying to device 'KVPBB18209202450'.
none
Skipping build...
Built the following apk(s):

    E:\qns-mobile\platforms\android\app\build\outputs\apk\debug\app-debug.apk

Using apk: E:qns-mobileplatformsandroidappbuildoutputsapkdebugapp-debug.apk
Package name: cn.evun.qns
(node:25828) UnhandledPromiseRejectionWarning: Error: C:Program FilesAndroidandroid-sdkplatform-toolsadb.exe: Command failed with exit code 1 Error output:
adb: failed to install E:qns-mobileplatformsandroidappbuildoutputsapkdebugapp-debug.apk: Failure [INSTALL_FAILED_UPDATE_INCOMPATIBLE: Package cn.evun.qns signatures do not match the previously installed version; ignoring!]

at ChildProcess.whenDone (E:\qns-mobile\platforms\android\cordova\node_modules\cordova-common\src\superspawn.js:169:23)
at emitTwo (events.js:126:13)
at ChildProcess.emit (events.js:214:7)
at maybeClose (internal/child_process.js:925:16)
at Process.ChildProcess._handle.onexit (internal/child_process.js:209:5)

(node:25828) UnhandledPromiseRejectionWarning: Unhandled promise rejection. This error originated either by throwing inside of an async function without a catch block, or by rejecting a promise which was not handled with .catch(). (rejection id: 1)
(node:25828) [DEP0018] DeprecationWarning: Unhandled promise rejections are deprecated. In the future,
promise rejections that are not handled will terminate the Node.js process with a non-zero exit code.
PS E:qns-mobile>

是我哪里出错了？ 困扰了一天
求大神指教...