Navigation -- realize data transmission and data sharing between fragments

Navigation chart Arugments Static transfer

In the built multi visual navigation map , Select the one that needs to accept data Fragment, For example, select here detailFragment.

And then in Attributes Hurdles Arguments Click “+” Button to add key value pairs , Fill in the name of the data to be transferred 、 type 、 Value and so on .

And then in DetailFragment.java Write code in the file to accept data , As follows ：

adopt **getArguments().getString(“name”)** get data ,getArugments The specific method to call depends on the data type .

public class DetailFragment extends Fragment {
    

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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_detail, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    
        super.onViewCreated(view, savedInstanceState);
        TextView tv = view.findViewById(R.id.tv1); 
        String text = getArguments().getString("name"); //  adopt getArguments().getString("name") get data 
        tv.setText(text);
    }
}

Bundle

Use Argument The method of adding key value pairs to transmit data can only achieve static transmission , If the data is dynamic , Then this method is difficult to achieve . adopt Bundle Method to realize data transmission is also very simple , Just create Bundle object , Then add key value pairs , When you switch pages, you will Bundle Just pass the object , The method of getting data from the page receiving data remains unchanged .

HomeFragment.java

public class HomeFragment extends Fragment {
    


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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    
        // Inflate the layout for this fragment
        return inflater.inflate(R.layout.fragment_home, container, false);
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    
        super.onViewCreated(view, savedInstanceState);
        Button button = view.findViewById(R.id.btn1);
        button.setOnClickListener(new View.OnClickListener() {
    
            @Override
            public void onClick(View v) {
    
                Bundle bundle = new Bundle();
                bundle.putString("name"," Xiaohong ");
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_homeFragment_to_detailFragment,bundle);
            }
        });
    }
}

adopt ViewModel+LiveData+Databinding Realization Fragment Data sharing and transmission between

Create two Fragment, Write the layout , Realize data binding in layout , Build the navigation map , The final effect is shown in the figure below , How to implement it will not be introduced in detail , Because this is mainly about how to realize data sharing . You can see in the jump process of the page , The numbers have not changed .

Customize ViewModel class ：

public class MyViewModel extends ViewModel {
    

    private MutableLiveData<Integer> liveData;

    public MutableLiveData<Integer> getCurrent() {
    
        if(liveData == null) {
    
            liveData = new MutableLiveData<Integer>();
            liveData.setValue(0); //  You have to set , Otherwise, null pointer exceptions may occur when obtaining .
        }
        return liveData;
    }

    public void add(int num) {
    
        liveData.setValue(liveData.getValue() + num);
    }

}

stay HomeFragment Class onCreateView In the method , Perform data binding , Different from the previous data binding , It used to be setContentView To set the layout file , And here is using inflate To set the layout file .

For one Activity Two or more of Fragment, Because of these Fragment Subordinate Activity Is the same , In these Fragment Use in getActivity() Method gets the same Activity, So pass ViewModelProvider Acquired ViewModel It's the same object , This is also the meaning of singleton mode , So we can achieve Fragment Data sharing between .

HomeFragment.java

public class HomeFragment extends Fragment implements View.OnClickListener {
    

    private MyViewModel viewModel;

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

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    
        // Inflate the layout for this fragment
        //  Data binding 
        FragmentHomeBinding binding = DataBindingUtil.inflate(inflater,R.layout.fragment_home,container,false);
        viewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        binding.setData(viewModel);
        binding.setLifecycleOwner(getActivity());
        return binding.getRoot();
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    
        super.onViewCreated(view, savedInstanceState);
        Button button = view.findViewById(R.id.btn1);
        Button addBtn = view.findViewById(R.id.addBtn);
        Button subBtn = view.findViewById(R.id.subBtn);

        button.setOnClickListener(this);
        addBtn.setOnClickListener(this);
        subBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
    
        switch (v.getId()) {
    
            case R.id.btn1:
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_homeFragment_to_detailFragment2);
                break;
            case R.id.addBtn:
                viewModel.add(1);
                break;
            case R.id.subBtn:
                viewModel.add(-1);
                break;
        }
    }
}

stay DetailFragment Class is similar .

DetailFragment.java

public class DetailFragment extends Fragment implements View.OnClickListener{
    

    private MyViewModel viewModel;

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


    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container,
                             Bundle savedInstanceState) {
    
        FragmentDetailBinding binding = DataBindingUtil.inflate(inflater,R.layout.fragment_detail,container,false);
        viewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        binding.setData(viewModel);
        binding.setLifecycleOwner(getActivity());
        return binding.getRoot();
    }

    @Override
    public void onViewCreated(@NonNull View view, @Nullable Bundle savedInstanceState) {
    
        super.onViewCreated(view, savedInstanceState);
        Button button = view.findViewById(R.id.btn1);
        Button addBtn = view.findViewById(R.id.addBtn);
        Button subBtn = view.findViewById(R.id.subBtn);

        button.setOnClickListener(this);
        addBtn.setOnClickListener(this);
        subBtn.setOnClickListener(this);
    }

    @Override
    public void onClick(View v) {
    
        MyViewModel viewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        switch (v.getId()) {
    
            case R.id.btn1:
                NavController controller = Navigation.findNavController(v);
                controller.navigate(R.id.action_detailFragment_to_homeFragment);
                break;
            case R.id.addBtn:
                viewModel.add(1);
                break;
            case R.id.subBtn:
                viewModel.add(-1);
                break;
        }
    }
}

Project address ：https://gitee.com/yxl-17/jet-pack_-navigation