Navigation(3)_navigation 3-CSDN博客

本文链接：https://blog.csdn.net/ArtinCode/article/details/106608288

本文详细介绍了如何在Android应用中利用ViewModel和LiveData组件进行数据状态管理，包括创建MyViewModel类，定义数据操作函数，以及在MasterFragment和DetailFragment中通过Navigation进行页面跳转和数据绑定。

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APP架构：一个Activity通过Navigation导航到多个fragment

示例：
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//MyViewModel
//创建MyViewModel类，在类内定义LiveData
//定义数据操作的函数
public class MyViewModel extends ViewModel  {
    private MutableLiveData<Integer>number;

    public MutableLiveData<Integer>getNumber(){
        if(number == null){
            number = new MutableLiveData<>();
            number.setValue(0);
        }
        return number;
    }
    public void add(int x) {
        number.setValue(number.getValue() + x);
        if(number.getValue() < 0) {
            number.setValue(0);
        }
    }
}

/**
 * 定义主页面Fgment
 * //在匿名内部类中调用需要加final修饰符
 *
 * 1.创建myViewModel对象
 * 2.关联viewmodel和activity
 * 3.创建碎片binding类对象
 * 4.binding XML
 * 5.binding 数据源
 * 6.binding 观察者
 *
 *
 */
public class MasterFragment extends Fragment {


    public MasterFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        //在匿名内部类中调用需要加final修饰符
        final MyViewModel myViewModel;

        myViewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        FragmentMasterBinding binding;
        binding = DataBindingUtil.inflate(inflater,R.layout.fragment_master,container,false);
        binding.setData(myViewModel);
        binding.setLifecycleOwner(getActivity());

        binding.button.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_masterFragment_to_detailFragment);
            }
        });
        binding.seekBar.setProgress(myViewModel.getNumber().getValue());

        binding.seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() {
            @Override
            public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
                myViewModel.getNumber().setValue(progress);
            }

            @Override
            public void onStartTrackingTouch(SeekBar seekBar) {
                
            }

            @Override
            public void onStopTrackingTouch(SeekBar seekBar) {

            }
        });
        return binding.getRoot();
    }
}

//同理，通过设置viewmodel，livedata，binding后
// 数据的操作在View Model类内，Fgment内只留下导航代码，控件代码
public class DetailFragment extends Fragment {

    MyViewModel myViewModel ;

    public DetailFragment() {
        // Required empty public constructor
    }


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {

        myViewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        FragmentDetailBinding binding;
        binding = DataBindingUtil.inflate(inflater,R.layout.fragment_detail,container,false);
        binding.setData(myViewModel);
        binding.setLifecycleOwner(getActivity());

        binding.button4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                NavController navController = Navigation.findNavController(v);
                navController.navigate(R.id.action_detailFragment_to_masterFragment);
            }
        });
        return binding.getRoot();


    }
}