Gradle sync failed: Could not find com.android.tools.build:gradle:2.3.3.
Searched in the following locations:
https://repo1.maven.org/maven2/com/android/tools/build/gradle/2.3.3/gradle-2.3.3.pom
https://repo1.maven.org/maven2/com/android/tools/build/gradle/2.3.3/gradle-2.3.3.jar
Required by:
project :volley
Consult IDE log for more details (Help | Show Log) (4s 813ms)
经过一番排查，问题解决；
问题原因：
build.gradle 用的是 mavenCentral(); 而maven 中只有最高2.3.0
没有所需的2.3.3，所以，解决办法是：
不用mavenCentral ， 改为用：jcenter();
最后问题解决