public class MainActivity extends AppCompatActivity {
    FreeDrawView mSignatureView;

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

        mSignatureView = (FreeDrawView) findViewById(R.id.your_id);

        // Setup the View
        mSignatureView.setPaintColor(Color.BLACK);
        mSignatureView.setPaintWidthPx(getResources.getDimensionPixelSize(R.dimen.paint_width));
        //mSignatureView.setPaintWidthPx(12);
        mSignatureView.setPaintWidthDp(getResources.getDimension(R.dimen.paint_width));
        //mSignatureView.setPaintWidthDp(6);
        mSignatureView.setPaintAlpha(255);// from 0 to 255
        mSignatureView.setResizeBehaviour(ResizeBehaviour.CROP);// Must be one of ResizeBehaviour
                                                                // values;

        // This listener will be notified every time the path done and undone count changes
        mSignatureView.setPathRedoUndoCountChangeListener(new PathRedoUndoCountChangeListener() {
                                  @Override
                                  public void onUndoCountChanged(int undoCount) {
                                      // The undoCount is the number of the paths that can be undone
                                  }

                                  @Override
                                  public void onRedoCountChanged(int redoCount) {
                                      // The redoCount is the number of path removed that can be redrawn
                                  }
                              });
        // This listener will be notified every time a new path has been drawn
        mSignatureView.setOnPathDrawnListener(new PathDrawnListener() {
                    @Override
                    public void onNewPathDrawn() {
                        // The user has finished drawing a path
                    }

                    @Override
                    public void onPathStart() {
                        // The user has started drawing a path
                    }
                });

        // This will take a screenshot of the current drawn content of the view
        mSignatureView.getDrawScreenshot(new FreeDrawView.DrawCreatorListener() {
                                  @Override
                                  public void onDrawCreated(Bitmap draw) {
                                      // The draw Bitmap is the drawn content of the View
                                  }

                                  @Override
                                  public void onDrawCreationError() {
                                      // Something went wrong creating the bitmap, should never
                                      // happen unless the async task has been canceled
                                  }
                              });
    }
}

        FreeDrawSerializableState state = mSignatureView.getCurrentViewStateAsSerializable();// This returns a FreeDrawSerializableState (which implements Serializable)

        // Save this "state" object into a file or keep it where you want

        mSignatureView.restoreStateFromSerializable(state);// Restore the state of the view

        // Now all the previous paths and points have been restored (including the history)