Android Studio 在命令行编译工程

在Android sdk 目录下的samples/android-21/ 文件夹下，任找一个工程，如果在命令行直接编译

可能会报这种错误：

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)

如果是这样，首先回到工程目录下，运行

./gradlew
./gradlew  build

然后再执行进行编译

gradle build
gradle tasks //查看android gradle的所有任务
 gradle compileReleaseSource  //生成debug apk ，在build/outpus/apk 文件夹下