Weixin public doc

Download the Android SDK before development as instructed in Resource Center > Development Resource > Resource Download > Android Resource Download.

API: WXLaunchMiniProgram Example of the redirect from a mobile app to a Mini Program:

String appId = "wxd930ea5d5a258f4f"; // Enter the AppID
IWXAPI api = WXAPIFactory.createWXAPI(context, appId);

WXLaunchMiniProgram.Req req = new WXLaunchMiniProgram.Req();
req.userName = "gh_d43f693ca31f"; // Enter the Mini Program's original ID
req.path = path;                  // Path that can contain parameters, used to launch a page of the Mini Program. If it is not specified, the homepage of the Mini Program is launched by default.
req.miniprogramType = WXLaunchMiniProgram.Req.MINIPTOGRAM_TYPE_RELEASE;// Select to open one of the following versions: developer version, test version, and release version
api.sendReq(req);

Callback Description

In WXEntryActivity

public void onResp(BaseResp resp) {
    if (resp.getType() == ConstantsAPI.COMMAND_LAUNCH_WX_MINIPROGRAM) {
        WXLaunchMiniProgram.Resp launchMiniProResp = (WXLaunchMiniProgram.Resp) resp;
        String extraData =launchMiniProResp.extMsg; //The app-parameter property of the appropriate Mini Program component <button open-type="launchApp">
    }
}

For complete demo, refer to the Sample project at the official website.
For information on the redirect back from the Mini Program to the mobile app, refer to <a href="https://developers.weixin.qq.com/miniprogram/dev/api/launchApp.html"target="_blank">Mini Program Development Document.