BottomNavigationView以编程方式设置选定项的背景色

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

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.item_id:
                setItemBackground(item, Color.RED);
                break;
            // 其他选项卡的处理
        }
        return true;
    }
});

private void setItemBackground(MenuItem item, int color) {
    BottomNavigationMenuView menuView = (BottomNavigationMenuView) bottomNavigationView.getChildAt(0);
    View itemView = menuView.getChildAt(menuView.indexOfChild((View) item.getActionView()));
    itemView.setBackgroundColor(color);
}

bottomNavigationView.setOnNavigationItemSelectedListener(new BottomNavigationView.OnNavigationItemSelectedListener() {
    @Override
    public boolean onNavigationItemSelected(@NonNull MenuItem item) {
        switch (item.getItemId()) {
            case R.id.item_id:
                item.setCheckable(true);
                item.setChecked(true);
                bottomNavigationView.setItemBackgroundResource(R.color.selected_color);
                break;
            // 其他选项卡的处理
        }
        return true;
    }
});