MainPip.java

public class MainActivity extends AppCompatActivity {

    @BindView(R.id.videoView)
    VideoView mVideoView;

    @BindView(R.id.progrss)
    ProgressBar progressBar;

    @BindView(R.id.btn_play)
    ImageButton mPlay;

    @BindView(R.id.btn_pip)
    ImageButton mPip;

    @BindView(R.id.toolbar)
    Toolbar toolbar;

    private MediaController mediacontroller;
    private Uri uri;


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

        setSupportActionBar(toolbar);
        getSupportActionBar().setTitle("Picture in Picture");

        mediacontroller = new MediaController(this);
        mediacontroller.setAnchorView(mVideoView);
        String uriPath = "http://commondatastorage.googleapis.com/gtv-videos-bucket/sample/BigBuckBunny.mp4";
        uri = Uri.parse(uriPath);

        mPip.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if (android.os.Build.VERSION.SDK_INT >= 26) {
                    try {
                        Rational rational = new Rational(mVideoView.getWidth(),
                                mVideoView.getHeight());

                        PictureInPictureParams mParams =
                                new PictureInPictureParams.Builder()
                                        .setAspectRatio(rational)
                                        .build();

                        enterPictureInPictureMode(mParams);
                    } catch (IllegalStateException e) {
                        e.printStackTrace();
                    }
                } else {
                    Toast.makeText(MainActivity.this, "API 26 needed to perform PiP", Toast.LENGTH_SHORT).show();
                }
            }
        });
        mPlay.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                progressBar.setVisibility(View.VISIBLE);
                mVideoView.setMediaController(mediacontroller);
                mVideoView.setVideoURI(uri);
                mVideoView.requestFocus();
                mVideoView.start();
                mPlay.setVisibility(View.GONE);
            }
        });

        mVideoView.setOnPreparedListener(new MediaPlayer.OnPreparedListener() {
            @Override
            public void onPrepared(MediaPlayer mp) {
                progressBar.setVisibility(View.GONE);
            }
        });
    }

    @RequiresApi(api = Build.VERSION_CODES.O)
    @Override
    protected void onUserLeaveHint() {
        super.onUserLeaveHint();
        if (!isInPictureInPictureMode()) {
            Rational rational = new Rational(mVideoView.getWidth(),
                    mVideoView.getHeight());

            PictureInPictureParams mParams =
                    new PictureInPictureParams.Builder()
                            .setAspectRatio(rational)
                            .build();

            enterPictureInPictureMode(mParams);
        }
    }

    @Override
    public void onPictureInPictureModeChanged(boolean isInPictureInPictureMode) {
        super.onPictureInPictureModeChanged(isInPictureInPictureMode);

        if (isInPictureInPictureMode) {
            mPip.setVisibility(View.GONE);
            toolbar.setVisibility(View.GONE);
        } else {
            mPip.setVisibility(View.VISIBLE);
            toolbar.setVisibility(View.VISIBLE);
        }
    }
}