单Activity多Fragment，Navigation实现Fragment跳转，Fragment之间通过ViewModel共享数据

• 1、MainActivity
• 2、HomeFragment, DetailFragment
• • 2.1、HomeFragment
  • 2.2、DetailFragment
• 3、MyViewModel
• 参考

1、MainActivity

1、activity_main.xml

2、MainActivity

/*** kotlin_jetpack_navigation* 使用navigation  + dataBinding + viewModel* 三个fragment共享一个viewModel中的数据，在NavigationView中显示*/
class MainActivity : AppCompatActivity() {override fun onCreate(savedInstanceState: Bundle?) {super.onCreate(savedInstanceState)setContentView(R.layout.activity_main)}
}

2、HomeFragment, DetailFragment

• FragmentA：包括SeekBar和一个按钮，点击button跳转到FragmentB
• FragmentB：SeekBar加一和减一操作的按钮，一个返回FragmentA的按钮，即经过加减操作以后，在FragmentA上显示加减的结果。

nav_graph.xml

2.1、HomeFragment

1、fragment_home.xml

2、HomeFragment

class HomeFragment : Fragment() {override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {// Inflate the layout for this fragment
//        val myViewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)val myViewModel by activityViewModels()val binding = DataBindingUtil.inflate(inflater, R.layout.fragment_home, container, false)binding.also {it.data = myViewModelit.lifecycleOwner = activityit.button.setOnClickListener { v ->val controller = Navigation.findNavController(v)controller.navigate(R.id.action_homeFragment_to_detailFragment)}myViewModel.get().value?.also { numberValue ->it.seekBar.progress = numberValue}it.seekBar.setOnSeekBarChangeListener(object : SeekBar.OnSeekBarChangeListener {override fun onProgressChanged(p0: SeekBar?, p1: Int, p2: Boolean) {myViewModel.set(p1)}override fun onStartTrackingTouch(p0: SeekBar?) {}override fun onStopTrackingTouch(p0: SeekBar?) {}})}return binding.root}

2.2、DetailFragment

1、fragment_detail.xml

data.count(1)}"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toStartOf="@+id/jian"app:layout_constraintHorizontal_bias="0.5"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="@+id/guideline" />data.count(-1)}"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintHorizontal_bias="0.5"app:layout_constraintStart_toEndOf="@+id/add"app:layout_constraintTop_toTopOf="@+id/guideline" />

2、DetailFragment

class DetailFragment : Fragment() {override fun onCreateView(inflater: LayoutInflater, container: ViewGroup?,savedInstanceState: Bundle?): View? {// Inflate the layout for this fragment
//      val myViewModel = ViewModelProviders.of(this).get(MyViewModel::class.java)val myViewModel by activityViewModels()val binding = DataBindingUtil.inflate(inflater,R.layout.fragment_detail,container,false)binding.also {it.data = myViewModelit.lifecycleOwner = activityit.button3.setOnClickListener { v ->val controller = Navigation.findNavController(v)controller.navigate(R.id.action_detailFragment_to_homeFragment)}}return binding.root}}

3、MyViewModel

class MyViewModel : ViewModel() {var number: MutableLiveData = MutableLiveData(0)fun get() = numberfun set(result: Int) {number.value = result}fun count(x: Int) {number.value = number.value?.plus(x)if (number.value!! < 0)number.value = 0}
}

参考