build.gradle

//rootProject.file(): 取得根目錄中的檔案
def ksFile = rootProject.file('keystore.properties')
def props = new Properties();
if (ksFile.canRead()) {
  props.load(new FileInputStream(ksFile))
  if (props != null) {
    android.signingConfigs.sign.storeFile file(props['KEYSTORE_FILE'])
    android.signingConfigs.sign.storePassword props['KEYSTORE_PASSWORD']
    android.signingConfigs.sign.keyAlias props['KEYSTORE_ALIAS']
    android.signingConfigs.sign.keyPassword props['KEYSTORE_ALIAS_PASSWORD']
  } else {
    println 'some entries in \'keystore.properties\' not found!'
  }
} else {
  println '\'keystore.properties\' not found!'
}