androidx.recyclerview.widget.RecyclerView#smoothScrollToPosition ( )源码实例Demo

public static void scrollToTop(RecyclerView recyclerView) {
    RecyclerView.LayoutManager manager = recyclerView.getLayoutManager();
    int firstVisibleItemPosition = 0;
    if (manager instanceof LinearLayoutManager) {
        firstVisibleItemPosition = getFirstVisibleItemPosition((LinearLayoutManager) manager);
    } else if (manager instanceof StaggeredGridLayoutManager) {
        firstVisibleItemPosition = getFirstVisibleItemPosition((StaggeredGridLayoutManager) manager);
    }
    if (firstVisibleItemPosition > 5) {
        recyclerView.scrollToPosition(5);
    }
    recyclerView.smoothScrollToPosition(0);

    MysplashActivity activity = MysplashApplication.getInstance().getTopActivity();
    if (activity != null) {
        ComponentFactory.getSettingsService().notifySetBackToTop(activity);
    }
}
 

@Override public void scrollToTop() {
  RecyclerView list;
  if (followedStoresResultList.getVisibility() == View.VISIBLE) {
    list = followedStoresResultList;
  } else {
    list = allStoresResultList;
  }
  LinearLayoutManager layoutManager = ((LinearLayoutManager) list.getLayoutManager());
  int lastVisibleItemPosition = layoutManager.findLastVisibleItemPosition();
  if (lastVisibleItemPosition > 10) {
    list.scrollToPosition(10);
  }
  list.smoothScrollToPosition(0);
}
 

@Override @UiThread public void scrollToTop() {
  RecyclerView view = getRecyclerView();
  LinearLayoutManager layoutManager = ((LinearLayoutManager) view.getLayoutManager());
  int lastVisibleItemPosition = layoutManager.findLastVisibleItemPosition();
  if (lastVisibleItemPosition > 10) {
    view.scrollToPosition(10);
  }
  view.smoothScrollToPosition(0);
}
 

@Config(shadows = ShadowRecyclerView.class)
@Test
public void testScrollToTop() {
    verify(userManager).getUser(eq("username"), userCaptor.capture());
    userCaptor.getValue().onResponse(user);
    RecyclerView recyclerView = (RecyclerView) activity.findViewById(R.id.recycler_view);
    recyclerView.smoothScrollToPosition(1);
    assertThat(customShadowOf(recyclerView).getScrollPosition()).isEqualTo(1);
    TabLayout.Tab tab = ((TabLayout) activity.findViewById(R.id.tab_layout)).getTabAt(0);
    tab.select();
    tab.select();
    assertThat(customShadowOf(recyclerView).getScrollPosition()).isEqualTo(0);
}
 

@Override
public void perform(UiController uiController, View view) {
    RecyclerView recyclerView = (RecyclerView) view;
    recyclerView.smoothScrollToPosition(position);
}
 

@Config(shadows = ShadowRecyclerView.class)
@Test
public void testScrollToTop() {
    Intent intent = new Intent();
    intent.putExtra(ItemActivity.EXTRA_ITEM, new TestItem() {
        @NonNull
        @Override
        public String getType() {
            return STORY_TYPE;
        }

        @Override
        public String getId() {
            return "1";
        }

        @Override
        public boolean isStoryType() {
            return true;
        }

        @Override
        public int getKidCount() {
            return 10;
        }

        @Override
        public String getUrl() {
            return "http://example.com";
        }
    });
    controller = Robolectric.buildActivity(ItemActivity.class, intent);
    controller.create().start().resume();
    activity = controller.get();
    // see https://github.com/robolectric/robolectric/issues/1326
    ShadowLooper.pauseMainLooper();
    controller.visible();
    ShadowApplication.getInstance().getForegroundThreadScheduler().advanceToLastPostedRunnable();
    RecyclerView recyclerView = activity.findViewById(R.id.recycler_view);
    recyclerView.smoothScrollToPosition(1);
    assertThat(customShadowOf(recyclerView).getScrollPosition()).isEqualTo(1);
    TabLayout tabLayout = activity.findViewById(R.id.tab_layout);
    assertThat(tabLayout.getTabCount()).isEqualTo(2);
    tabLayout.getTabAt(1).select();
    tabLayout.getTabAt(0).select();
    tabLayout.getTabAt(0).select();
    assertThat(customShadowOf(recyclerView).getScrollPosition()).isEqualTo(0);
}