All datatable-rows are placed at the same row about gwt-material-table HOT 5 CLOSED

  public static class CustomCategoryComponent extends CategoryComponent {
    public CustomCategoryComponent(String category) {
      super(category);
    }

    @Override
    protected void render(TableSubHeader subheader) {
      super.render(subheader);

      subheader.setHeight("45px");    // Workaround 

      subheader.setOpenIcon(IconType.FOLDER_OPEN);
      subheader.setCloseIcon(IconType.FOLDER);
    }
  }

public class TestModule extends AbstractPresenterModule {
  @Override
  protected void configure() {
    install(new TestTab2Module());
    install(new TestTab1Module());
    bindPresenter(TestPresenter.class, TestPresenter.MyView.class, TestView.class, TestPresenter.MyProxy.class);
  }
}


public class TestPresenter extends Presenter<TestPresenter.MyView, TestPresenter.MyProxy> {

  public static final Slot<PresenterWidget<?>> SLOT_TAB1 = new Slot<>();
  public static final Slot<PresenterWidget<?>> SLOT_TAB2 = new Slot<>();

  private final TestTab1Presenter testTab1Presenter;
  private final TestTab2Presenter testTab2Presenter;

  interface MyView extends View {
  }

  @NameToken(NameTokens.TEST)
  @ProxyStandard
  interface MyProxy extends ProxyPlace<TestPresenter> {
  }

  @Inject
  TestPresenter(EventBus eventBus, MyView view, MyProxy proxy,
                TestTab1Presenter testTab1Presenter, TestTab2Presenter testTab2Presenter) {
    super(eventBus, view, proxy, ApplicationPresenter.SLOT_MAIN);
    this.testTab1Presenter = testTab1Presenter;
    this.testTab2Presenter = testTab2Presenter;
  }
  // Only for Menu-Title
  @Override
  protected void onReveal() {
    super.onReveal();
    SetMenuBarTitleEvent.fire("Test", this);
  }

  @Override
  protected void onBind() {
    super.onBind();
    setInSlot(SLOT_TAB1, testTab1Presenter);
    setInSlot(SLOT_TAB2, testTab2Presenter);
  }
}

<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
             xmlns:m="urn:import:gwt.material.design.client.ui"
>
  <m:MaterialPanel ui:field="panel" marginTop="64">
    <m:MaterialColumn grid="s12">
      <m:MaterialTab ui:field="testTab" type="ICON" backgroundColor="BLUE_GREY_LIGHTEN_5"
                     indicatorColor="BLUE_DARKEN_3">
        <m:MaterialTabItem ui:field="tab1Item" waves="DEFAULT">
          <m:MaterialLink text="Dummy" href="#tab1" textColor="BLACK" />
        </m:MaterialTabItem>
        <m:MaterialTabItem ui:field="tab2Item" waves="DEFAULT">
          <m:MaterialLink text="Persons" href="#tab2" textColor="BLACK" iconType="EQUALIZER"/>
        </m:MaterialTabItem>
      </m:MaterialTab>
    </m:MaterialColumn>

    <m:MaterialColumn m:id="tab1" grid="s12">
      <m:MaterialRow>
        <m:MaterialPanel ui:field="tab1Panel"/>
      </m:MaterialRow>
    </m:MaterialColumn>
    <m:MaterialColumn m:id="tab2" grid="s12">
      <m:MaterialPanel ui:field="tab2Panel"/>
    </m:MaterialColumn>
  </m:MaterialPanel>
</ui:UiBinder>


public class TestView extends ViewImpl implements TestPresenter.MyView {

  interface Binder extends UiBinder<MaterialPanel, TestView> {
  }

  @UiField
  MaterialPanel tab1Panel, tab2Panel;
  @UiField
  MaterialTabItem tab1Item, tab2Item;

  @Inject
  TestView(Binder binder) {
    initWidget(binder.createAndBindUi(this));
    bindSlot(TestPresenter.SLOT_TAB1, tab1Panel);
    bindSlot(TestPresenter.SLOT_TAB2, tab2Panel);
  }
}

public class TestTab2Module extends AbstractPresenterModule {
  @Override
  protected void configure() {
    bindPresenterWidget(TestTab2Presenter.class, TestTab2Presenter.MyView.class, TestTab2View.class);
  }
}


public class TestTab2Presenter extends PresenterWidget<TestTab2Presenter.MyView> implements TestTab2UiHandlers {

  private final RestDispatch dispatcher;
  private final TestSearchService testSearchService;

  interface MyView extends View, HasUiHandlers<TestTab2UiHandlers> {
    void setSearchTableData(List<TestDTO> result);
  }

  @Inject
  TestTab2Presenter(EventBus eventBus, MyView view, RestDispatch dispatcher, TestSearchService testSearchService) {
    super(eventBus, view);
    this.dispatcher = dispatcher;
    this.testSearchService = testSearchService;

    getView().setUiHandlers(this);
  }

  @Override
  protected void onBind() {
    super.onBind();
    dispatcher.execute(testSearchService.getPersons(), new AsyncCallback<List<TestDTO>>() {
      @Override
      public void onFailure(Throwable caught) {
        // Catch Failure
      }

      @Override
      public void onSuccess(List<TestDTO> result) {
        // REST-Response from DB all Person categorized
        // Category --> Simth
        // Category --> Bar
        getView().setSearchTableData(result);
      }
    });
  }
}

public class TestTab2View extends ViewWithUiHandlers<TestTab2UiHandlers> implements TestTab2Presenter.MyView {
  interface Binder extends UiBinder<HTMLPanel, TestTab2View> {
  }

  @UiField
  MaterialDataTable<TestDTO> table;

  @Inject
  TestTab2View(Binder binder) {
    initWidget(binder.createAndBindUi(this));

    table.setLoadedCallback(() -> {
      // We will define our own person row factory to generate the
      // category name. This can be used to generate your own
      // RowComponent's too, if custom functionality is required.
      table.setRowFactory(new TestPersonRowFactory());

      // If we want to generate all our categories using CustomCategoryComponent
      // We can define our own CategoryComponentFactory. There we can define our
      // own CategoryComponent implementations.
      table.setCategoryFactory(new TestPersonCategoryFactory());

      // Add the tables columns
      table.addColumn(new TextColumn<TestDTO>() {
        @Override
        public String getValue(TestDTO object) {
          return object.getFirstname();
        }
      }, "Firstname");

      table.addColumn(new TextColumn<TestDTO>() {
        @Override
        public String getValue(TestDTO object) {
          return object.getName();
        }
      }, "Name");

      table.addColumn(new TextColumn<TestDTO>() {
        @Override
        public HideOn getHideOn() {
          return HideOn.fromStyleName("hide-on-med-and-up");
        }

        @Override
        public String getValue(TestDTO object) {
          return String.valueOf(object.getId());
        }
      }, "Pers-ID");

    });
    //table.setDestroyOnUnload(false);
  }

  public void setSearchTableData(List<TestDTO> result) {
    table.setVisibleRange(0, result.size());
    table.setRowData(0, result);
    table.refreshView();
  }

  public static class CustomCategoryComponent extends CategoryComponent {
    public CustomCategoryComponent(String category) {
      super(category);
    }

    @SuppressWarnings("Duplicates")
    @Override
    protected void render(TableSubHeader subheader) {
      super.render(subheader);

      //subheader.setHeight("45px");    // Workaround for row override problem comment off if you need

      subheader.setTextColor(Color.BLUE_DARKEN_1);
      subheader.setOpenIcon(IconType.FOLDER_OPEN);
      subheader.setCloseIcon(IconType.FOLDER);
    }
  }

  public class TestPersonRowFactory extends RowComponentFactory<TestDTO> {
    @Override
    public RowComponent<TestDTO> generate(TestDTO model) {
      // We won't change the way it loads the RowComponent
      return super.generate(model);
    }
    @Override
    public String getCategory(TestDTO model) {
      // We want to override the standard category retrieval
      // This is where we can define a models category.
      // This is useful when we don't want to pollute our
      // object models with the interface HasDataCategory.
      return model.getCategory();
    }
  }

  public class TestPersonCategoryFactory extends CategoryComponentFactory {
    @Override
    public CategoryComponent generate(String categoryName) {
      CategoryComponent category = super.generate(categoryName);
      if (!(category instanceof CategoryComponent.OrphanCategoryComponent)) {
        category = new TestTab2View.CustomCategoryComponent(categoryName);
      }
      return category;
    }
  }
}

<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
             xmlns:m="urn:import:gwt.material.design.client.ui"
             xmlns:m.table="urn:import:gwt.material.design.client.ui.table"
             xmlns:g='urn:import:com.google.gwt.user.client.ui'>
  <g:HTMLPanel>
    <m:MaterialRow>
      <m.table:MaterialDataTable m:id="customTable" ui:field="table"
                                 height="calc(50vh)"
                                 useStickyHeader="true"
                                 useCategories="true"
                                 useRowExpansion="false"
                                 selectionType="SINGLE"/>
    </m:MaterialRow>
  </g:HTMLPanel>
</ui:UiBinder>

public class TestTab1Module extends AbstractPresenterModule {
  @Override
  protected void configure() {
    bindPresenterWidget(TestTab1Presenter.class, TestTab1Presenter.MyView.class, TestTab1View.class);
  }
}

public class TestTab1Presenter extends PresenterWidget<TestTab1Presenter.MyView> implements TestTab1UiHandlers {

  interface MyView extends View, HasUiHandlers<TestTab1UiHandlers> {
  }

  @Inject
  TestTab1Presenter(EventBus eventBus, MyView view) {
    super(eventBus, view);

    getView().setUiHandlers(this);
  }
}

public class TestTab1View extends ViewWithUiHandlers<TestTab1UiHandlers> implements TestTab1Presenter.MyView {
  interface Binder extends UiBinder<HTMLPanel, TestTab1View> {
  }

  @Inject
  TestTab1View(Binder binder) {
    initWidget(binder.createAndBindUi(this));
  }
}

<ui:UiBinder xmlns:ui='urn:ui:com.google.gwt.uibinder'
             xmlns:m="urn:import:gwt.material.design.client.ui"
             xmlns:g='urn:import:com.google.gwt.user.client.ui'>
  <g:HTMLPanel>
    <m:MaterialRow addStyleNames="code">
      <m:MaterialColumn grid="s12">
        <m:MaterialLabel text="DUMMY - TAB"/>
      </m:MaterialColumn>
    </m:MaterialRow>
  </g:HTMLPanel>
</ui:UiBinder>

public class TestDTO {

  private long id;
  private String firstname;
  private String name;
  private String category;

  public TestDTO() {
  }

  // Getter and Setter .....
}