BottomNavigationView

Question

我使用了BottomNavigationView来切换片段。如何获取当前选定的菜单项，以防止重新打开片段？

        BottomNavigationView bottomNavigationView = (BottomNavigationView)
                findViewById(R.id.bottom_navigation);

        bottomNavigationView.setOnNavigationItemSelectedListener(
                new BottomNavigationView.OnNavigationItemSelectedListener() {
                    @Override
                    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
                        switch (item.getItemId()) {
                            case R.id.action_1:
                                // open fragment 1
                                break;
                            case R.id.action_2:
                                // open fragment 2
                                break;
                            case R.id.action_3:
                                // open fragment 3
                                break;
                        }
                        return false;
                    }
                });
    }

Answer 1

解决方案：

private int getSelectedItem(BottomNavigationView bottomNavigationView) {
    Menu menu = bottomNavigationView.getMenu();
    for (int i = 0; i < bottomNavigationView.getMenu().size(); i++) {
        MenuItem menuItem = menu.getItem(i);
        if (menuItem.isChecked()) {
            return menuItem.getItemId();
        }
    }
    return 0;
}

Answer 2

使用getSelectedItemId获取当前选择的菜单项ID:

int selectedItemId = bottomNavigationView.getSelectedItemId();
MenuItem selectedItem = bottomNavigationView.getMenu().findItem(selectedItemId);

此方法从 Android 支持库 25.3.0 开始可用。

Answer 3

先获取选中项，然后getMenu().findItem(int itemId)

bottomNavigationView.getMenu().findItem(bottomNavigationView.getSelectedItemId())

Answer 4

我认为检查上一项是否是下一项的最简单解决方案是：

BottomNavigationView bottomNavigationView = (BottomNavigationView) findViewById(R.id.bottom_navigation);

bottomNavigationView.setOnNavigationItemSelectedListener(
    new BottomNavigationView.OnNavigationItemSelectedListener() {
        @Override
        public boolean onNavigationItemSelected(@NonNull MenuItem item) {
            final int previousItem = bottomNavigationView.getSelectedItemId();
            final int nextItem = item.getItemId();
            if (previousItem != nextItem) {
                 switch (nextItem) {
                     case R.id.action_1:
                         // open fragment 1
                         break;
                     case R.id.action_2:
                         // open fragment 2
                         break;
                     case R.id.action_3:
                         // open fragment 3
                         break;
                 }
            }
            return true;
        }
    }
);

注意不需要迭代，而且onNavigationItemSelectedreturnstrue，因为函数消费了事件

希望对大家有所帮助。

BottomNavigationView - 如何获取选定的菜单项？

BottomNavigationView - How to get selected menu item?

android