Missing Library Error

[RimakiTaema]

> Task :ImguiDemoSdl:compileDebugJavaWithJavac
/home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:7: error: package org.libsdl.app does not exist
import org.libsdl.app.SDLActivity;
                     ^
/home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:18: error: cannot find symbol
public class DemoActivity extends SDLActivity {
                                  ^
  symbol: class SDLActivity                                                             /home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:34: error: method does not override or implement a method from a supertype
    @Override
    ^
/home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:39: error: method does not override or implement a method from a supertype                                                                               @Override
    ^
/home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:41: error: cannot find symbol
        return new String[]{getFilesDir().getAbsolutePath()};
                            ^
  symbol:   method getFilesDir()
  location: class DemoActivity
/home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:44: error: method does not override or implement a method from a supertype                                                                               @Override                                                                               ^                                                                                   /home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:47: error: cannot find symbol                                        super.onCreate(savedInstanceState);
        ^                                                                                 symbol:   variable super
  location: class DemoActivity
/home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:52: error: cannot find symbol
        AssetManager assetManager = this.getAssets();                                                                           ^
  symbol: method getAssets()                                                            /home/rimaki/Imgui_Android-as-jellyfish-update/ImguiDemoSdl/src/main/java/me/sfalexrog/imguidemo/DemoActivity.java:57: error: cannot find symbol
                FileOutputStream fos = openFileOutput(assetName, MODE_PRIVATE);                                                                          ^
  symbol:   variable MODE_PRIVATE
  location: class DemoActivity
9 errors

> Task :ImguiDemoSdl:compileDebugJavaWithJavac FAILED

FAILURE: Build failed with an exception.

* What went wrong:
Execution failed for task ':ImguiDemoSdl:compileDebugJavaWithJavac'.
> Compilation failed; see the compiler error output for details.

* Try:
> Run with --info option to get more log output.
> Run with --scan to get full insights.

BUILD FAILED in 5m 38s
19 actionable tasks: 19 executed
rimaki@RimakiServer:~/Imgui_Android-as-jellyfish-update$ 

how do i fix this
(and it's your time to update repo)