一、React-Native在6.0以下Android手机运行调试
默认$react-native run-android需要android6.0以上才能成功安装应用
如何降低版本：
1、修改 项目根目录\android\build.gradle
dependencies {
//classpath 'com.android.tools.build:gradle:2.2.3'
classpath 'com.android.tools.build:gradle:1.2.3'
// NOTE: Do not place your application dependencies here; they belong
// in the individual module build.gradle files
}
再次执行$react-native run-android会提示修改 项目根目录\android\gradle\wrapper\gradle-wrapper.properties
distributionBase=GRADLE_USER_HOME
distributionPath=wrapper/dists
zipStoreBase=GRADLE_USER_HOME
zipStorePath=wrapper/dists
#distributionUrl=https\://services.gradle.org/distributions/gradle-2.14.1-all.zip
distributionUrl=https\://services.gradle.org/distributions/gradle-2.2-all.zip
再次执行$react-native run-android会下载gradle-2.2-all.zip(下载速度比较慢)，操作成功(我手机是android5.1)