demo编译不通过

[pion-zou]

Could not find com.android.support.constraint:constraint-layout:1.0.0-beta4.
Searched in the following locations:
file:/Users/jane/Library/Android/sdk/extras/m2repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.pom
file:/Users/jane/Library/Android/sdk/extras/m2repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.jar
file:/Users/jane/Library/Android/sdk/extras/google/m2repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.pom
file:/Users/jane/Library/Android/sdk/extras/google/m2repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.jar
file:/Users/jane/Library/Android/sdk/extras/android/m2repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.pom
file:/Users/jane/Library/Android/sdk/extras/android/m2repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.jar
file:/Users/jane/.m2/repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.pom
file:/Users/jane/.m2/repository/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.jar
https://dl.google.com/dl/android/maven2/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.pom
https://dl.google.com/dl/android/maven2/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.jar
http://jcenter.bintray.com/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.pom
http://jcenter.bintray.com/com/android/support/constraint/constraint-layout/1.0.0-beta4/constraint-layout-1.0.0-beta4.jar
Required by:
project :app