Untitled

import android.net.Uri;
import android.os.Bundle;
import android.widget.Button;
import android.widget.VideoView;
import androidx.appcompat.app.AppCompatActivity;
import java.io.File;
import java.io.IOException;

public class MainActivity extends AppCompatActivity {

    private VideoView videoView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        videoView = findViewById(R.id.videoView);
        Button mergeButton = findViewById(R.id.mergeButton);
        Button playButton = findViewById(R.id.playButton);

        try {
            String inputFile1 = FileUtil.copyRawFileToInternalStorage(this, R.raw.video1, "video1.mp4");
            String inputFile2 = FileUtil.copyRawFileToInternalStorage(this, R.raw.video2, "video2.mp4");
            String outputFile = new File(getFilesDir(), "merged_video.mp4").getAbsolutePath();

            mergeButton.setOnClickListener(v -> {
                VideoMerger videoMerger = new VideoMerger();
                try {
                    videoMerger.mergeVideos(inputFile1, inputFile2, outputFile);
                } catch (IOException e) {
                    e.printStackTrace();
                }
            });

            playButton.setOnClickListener(v -> playMergedVideo(outputFile));

        } catch (IOException e) {
            e.printStackTrace();
        }
    }

    private void playMergedVideo(String outputFile) {
        videoView.setVideoURI(Uri.parse(outputFile));
        videoView.start();
    }
}