在遇到adb 命令不识别，或者genymotion的模拟器不识别，找不到的问题。都是genymotion配置的不正确。
打开genymotion的adb设置，androidSDK的配置选择自己下载的androidsdk,而不是genymotion默认的选项就可以解决了。
如下是我遇到的错误：
S server already running.
Building and installing the app on the device (cd android && ./gradlew installDebug)...
:app:preBuild UP-TO-DATE
:app:preDebugBuild UP-TO-DATE
:app:checkDebugManifest
:app:preReleaseBuild UP-TO-DATE
:app:prepareComAndroidSupportAppcompatV72301Library UP-TO-DATE
:app:prepareComAndroidSupportRecyclerviewV72301Library UP-TO-DATE
:app:prepareComAndroidSupportSupportV42301Library UP-TO-DATE
:app:prepareComFacebookFrescoDrawee081Library UP-TO-DATE
:app:prepareComFacebookFrescoFbcore081Library UP-TO-DATE
:app:prepareComFacebookFrescoFresco081Library UP-TO-DATE
:app:prepareComFacebookFrescoImagepipeline081Library UP-TO-DATE
:app:prepareComFacebookFrescoImagepipelineOkhttp081Library UP-TO-DATE
:app:prepareComFacebookReactReactNative0222Library UP-TO-DATE
:app:prepareOrgWebkitAndroidJscR174650Library UP-TO-DATE
:app:prepareDebugDependencies
:app:compileDebugAidl UP-TO-DATE
:app:compileDebugRenderscript UP-TO-DATE
:app:generateDebugBuildConfig UP-TO-DATE
:app:generateDebugAssets UP-TO-DATE
:app:mergeDebugAssets UP-TO-DATE
:app:generateDebugResValues UP-TO-DATE
:app:generateDebugResources UP-TO-DATE
:app:mergeDebugResources UP-TO-DATE
:app:bundleDebugJsAndAssets SKIPPED
:app:processDebugManifest UP-TO-DATE
:app:processDebugResources UP-TO-DATE
:app:generateDebugSources UP-TO-DATE
:app:processDebugJavaRes UP-TO-DATE
:app:compileDebugJavaWithJavac UP-TO-DATE
:app:compileDebugNdk UP-TO-DATE
:app:compileDebugSources UP-TO-DATE
:app:preDexDebug UP-TO-DATE
:app:dexDebug UP-TO-DATE
:app:validateDebugSigning
:app:packageDebug UP-TO-DATE
:app:zipalignDebug UP-TO-DATE
:app:assembleDebug UP-TO-DATE
:app:installDebug Failed
FAILURE: Build Failed with an exception.
What went wrong:
Execution Failed for task ':app:installDebug'.
com.android.builder.testing.api.DeviceException: No connected devices!
Try:
Run with --stacktrace option to get the stack trace. Run with --info or --debug option to get more log output.
BUILD Failed
Total time: 15.174 secs
Could not install the app on the device,read the error above for details.
Make sure you have an Android emulator running or a device connected and have
set up your Android development environment:
https://facebook.github.io/react-native/docs/android-setup.html
