造成的原因是项目的build target版本和安装的Andriod SDK Tools版本不一致.
Unable to build: the file dx.jar was not loaded from the SDK folder
Unable to build: the file dx.jar was not loaded from the SDK folder
下载API25,将API25的dx.jar替换API29的(可以对API29的dx.jar先做一个拷贝).
Unable to build: the file dx.jar was not loaded from the SDK folder
替换
Unable to build: the file dx.jar was not loaded from the SDK folder
clean项目,或重启eclipse

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