我有一个底部导航视图,其中有3个项目,它们导航到3个不同的片段(片段仅创建一次,并将它们的实例保存在MainActivity的onSavedInstanceState()中),并在其上方有一个浮动操作按钮。
当访问每个片段时,我们想要更改fab的图标可绘制对象,我们尝试在switch case中选择每个底部导航图标时使用setImageResource()
和.setImageDrawable()
在fab上。
/**
* used to handle switching between fragments when a new navigation item is selected
*/
@Override
public boolean onNavigationItemSelected(@NonNull MenuItem item) {
switch (item.getItemId()) {
case R.id.nav_tasks:
.........
loadFragment(tasksFragment);
mFab.setOnClickListener(mFabClickListenerTasks);
mFab.setImageDrawable(getResources().getDrawable(R.drawable.ic_add_task));
//2 tabs in 1 fragment
if (mTabLayout.getSelectedTabPosition() == 1)
mFab.hide();
else mFab.show();
break;
case R.id.nav_employees:
.......
loadFragment(employeesFragment);
mFab.setOnClickListener(mFabClickListenerEmployees);
mFab.setImageDrawable(getResources().getDrawable(R.drawable.ic_add_employee2));
mFab.show();
break;
case R.id.nav_departments:
.......
loadFragment(departmentsFragment);
mFab.setOnClickListener(mFabClickListenerDepartments);
mFab.setImageDrawable(getResources().getDrawable(R.drawable.ic_add_department));
mFab.show();
break;
}
item.setChecked(true);
return true;
}
void loadFragment(Fragment fragment) {
if (activeFragment == fragment)
return;
FragmentTransaction transaction = getSupportFragmentManager().beginTransaction();
transaction.hide(activeFragment).show(fragment);
activeFragment = fragment;
transaction.setTransition(FragmentTransaction.TRANSIT_FRAGMENT_OPEN);
if (activeFragment instanceof TasksFragment)
mFab.setImageResource(R.drawable.ic_add_task);
else if(activeFragment instanceof DepartmentsFragment)
mFab.setImageResource(R.drawable.ic_add_department);
else if(activeFragment instanceof EmployeesFragment)
mFab.setImageResource(R.drawable.ic_add_employee2);
transaction.commit();
}
这3个片段主要是3个回收站视图,当recyclerview滚动时,我们也会隐藏fab。
从底部导航遍历片段时,fab drawable将被正确设置,但在任何片段中,当我们滚动时,它保存此状态以便以后返回。
这将在转到另一个片段时删除fab drawable,并使fab为空,没有图标可绘制。我们该如何解决这个问题?