Android Studio 在命令行編譯工程

在Android sdk 目錄下的samples/android-21/ 文件夾下，任找一個工程，如果在命令行直接編譯

可能會報這種錯誤：

gradle buile.gradle

FAILURE: Build failed with an exception.  
  
* What went wrong:  
Task 'build.gradle' not found in root project 'BorderlessButtons'.  
  
* Try:  
Run gradle tasks to get a list of available tasks. Run with --info or --debug option to get more log output.  
  
* Exception is:  
org.gradle.execution.TaskSelectionException: Task 'build.gradle' not found in root project 'BorderlessButtons'.  
    at org.gradle.execution.TaskSelector.getSelection(TaskSelector.java:101)  
    at org.gradle.execution.TaskSelector.getSelection(TaskSelector.java:76)  
    at org.gradle.execution.commandline.CommandLineTaskParser.parseTasks(CommandLineTaskParser.java:42)  
    at org.gradle.execution.TaskNameResolvingBuildConfigurationAction.configure(TaskNameResolvingBuildConfigurationAction.java:44)  

./gradlew  
./gradlew  build

gradle build 
gradle tasks //查看android gradle的所有任務
 gradle compileReleaseSource  //生成debug apk ，在build/outpus/apk 文件夾下