Failure [INSTALL_FAILED_OLDER_SDK] error of Android development

    [size=xx-small] At first, I saw this error and rejected it, because I had no problem running the project on eclipse before. Later, after being instructed by a great god to "return the evil and return to the right", I switched to Android studio for development. This error appeared when everything was ready. Some big cows on the Internet said that the minimum version required for apk to run is higher than the android version of your real machine, so I adjusted android:minSdkVersion in AndroidManifest.xml to a suitable value, but it kept reporting the Failure [INSTALL_FAILED_OLDER_SDK] error. Changing the android:minSdkVersion value to 1 does not work. There is a feeling of wanting a Japanese dog.
    Later, after careful "exploration", I found that there is a build.gradle directory in the app directory of the project, and curiosity prompted me to open it. As the saying goes, "curiosity killed the cat", but this time I found something good out of curiosity. After opening, there are actually two lines of this thing: minSdkVersion 21 targetSdkVersion 21. Ah, it turns out that the culprit turned out to be it. Change the minSdkVersion here to a suitable value, and all the problems will be solved. Do you feel very stupid? *_* [/size]