android schema:

String url = "adb -s " + udid + " shell am start -a 'android.intent.action.VIEW' -d " + "'" + schemaUrl + "'";

android activity:

String url = "adb -s " + udid + " shell am start " + packageName + "/" + activityName;

ios?:

String[] cmd = {"/usr/local/bin/idevicedebug", "-u", udid, "run","com.apple.test.WebDriverAgentRunner-Runner"};

RuntimeUtil.Result r = RuntimeUtil.execWithResult(cmd, timeoutInSeconds, TimeUnit.SECONDS);
Driver driver = new AppiumDriver<MobileElement>();
driver.get(shcemUrl);