How to detect if an app is launched on a potentially rooted phone in an non-invasive way. It could be improved by checking existence of known super user apk in the package manager and certain build tags of the ROM.

RootStatus.java

package com.yourapp;

import java.io.File;

public final class RootStatus {

    private static RootStatus instance;

    private final boolean rooted;

    private RootStatus(final boolean rooted) {
        this.rooted = rooted;
    }

    private static synchronized RootStatus getInstance() {

        if (instance == null) {
            final boolean rooted = hasSuExecutable();
            instance = new RootStatus(rooted);
        }
        return instance;
    }

    private static boolean hasSuExecutable() {
        return binaryExists("su");
    }

    private static boolean binaryExists(final String binaryName) {
        final String[] places = {"/sbin/", "/system/bin/", "/system/xbin/", "/data/local/xbin/",
                "/data/local/bin/", "/system/sd/xbin/", "/system/bin/failsafe/", "/data/local/"};
        for (final String where : places) {
            if (new File(where, binaryName).exists()) {
                return true;
            }
        }
        return false;
    }

    public static boolean isRooted() {
        return getInstance().rooted;
    }
}

YourActivity.java

package com.yourapp;

// imports

public class YourActivity extends Activity {
    
    public void onCreate(Bundle savedInstance) {
        
        if(Rootstatus.isRooted() ){
            // OH NO!
        } else {
            // All good.
        }
    }
}

Did you try this on Lollipop? Doing File.exists() doesn't work on some system files, even if those have files have chmod 777. Only works if you are using a rooted process.

You can easily circumvent this kind of root detection by simply replacing the File.exists() method with xposed.

findAndHookMethod("java.io.File", lpparam.classLoader, "exists", new XC_MethodHook() {
    @Override
    protected void beforeHookedMethod(MethodHookParam param) throws Throwable {
        if (param.thisObject == null) {return;}
        File f = (File) param.thisObject;
        String sName = f.getPath();
        if (!sName.equals("/system/app/Superuser.apk") &&
                !sName.endsWith("/su"))
            return;
        param.setResult(false);
    }
});