[移动开发]Navigation 组件(三) ViewModel，LiveData，DataBinding 组合使用

1. Module 中 build.gradle 配置文件添加引用库

android {
    //AS 4.1 之后写法
    buildFeatures {
        dataBinding = true
    }
}

dependencies {
    implementation 'androidx.navigation:navigation-fragment:2.5.1'
    implementation 'androidx.navigation:navigation-ui:2.5.1'
}

2. MasterFragment页面

? 2.1 MasterFragment.java

public class MasterFragment extends Fragment {
    MyViewModel myViewModel;
    FragmentMasterBinding binding;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        myViewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        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 view) {
                NavController controller = Navigation.findNavController(view);
                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();
    }
}

? 2.2 fragment_master.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">
    <data>
        <variable
            name="data"
            type="com.example.navviewmodel.MyViewModel" />
    </data>
    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".MasterFragment">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(data.getNumber())}"
            android:textSize="24sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.224" />

        <SeekBar
            android:id="@+id/seekBar"
            android:layout_width="0dp"
            android:layout_height="wrap_content"
            android:max="10"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.39" />

        <Button
            android:id="@+id/button"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="进入"
            android:textSize="20sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

3. DetailFragment 页面

? 3.1 DetailFragment.java

public class DetailFragment extends Fragment {
    MyViewModel myViewModel;
    FragmentDetailBinding binding;

    @Override
    public View onCreateView(LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState) {
        myViewModel = new ViewModelProvider(getActivity()).get(MyViewModel.class);
        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 view) {
                NavController controller = Navigation.findNavController(view);
                controller.navigate(R.id.action_detailFragment_to_masterFragment);
            }
        });
        return binding.getRoot();
    }
}

? 3.2 fragment_detail.xml

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools">

    <data>

        <variable
            name="data"
            type="com.example.navviewmodel.MyViewModel" />
    </data>

    <androidx.constraintlayout.widget.ConstraintLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".DetailFragment">

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{String.valueOf(data.number)}"
            android:textSize="24sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.498"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.316" />

        <Button
            android:id="@+id/button2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="@{()->data.add(-1)}"
            android:text="—"
            android:textSize="24sp"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toStartOf="@+id/button3"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent" />

        <Button
            android:id="@+id/button3"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="@{()->data.add(1)}"
            android:text="+"
            android:textSize="24sp"
            app:layout_constraintBottom_toBottomOf="@+id/button2"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintHorizontal_bias="0.5"
            app:layout_constraintStart_toEndOf="@+id/button2"
            app:layout_constraintTop_toTopOf="@+id/button2" />

        <Button
            android:id="@+id/button4"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="返回"
            app:layout_constraintBottom_toBottomOf="parent"
            app:layout_constraintEnd_toEndOf="parent"
            app:layout_constraintStart_toStartOf="parent"
            app:layout_constraintTop_toTopOf="parent"
            app:layout_constraintVertical_bias="0.65" />
    </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

4. 创建 my_navigation.xml 导航控制器

<?xml version="1.0" encoding="utf-8"?>
<navigation xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/my_navigation"
    app:startDestination="@id/masterFragment">

    <fragment
        android:id="@+id/masterFragment"
        android:name="com.example.navviewmodel.MasterFragment"
        android:label="fragment_master"
        tools:layout="@layout/fragment_master" >
        <action
            android:id="@+id/action_masterFragment_to_detailFragment"
            app:destination="@id/detailFragment" />
    </fragment>
    <fragment
        android:id="@+id/detailFragment"
        android:name="com.example.navviewmodel.DetailFragment"
        android:label="fragment_detail"
        tools:layout="@layout/fragment_detail" >
        <action
            android:id="@+id/action_detailFragment_to_masterFragment"
            app:destination="@id/masterFragment" />
    </fragment>
</navigation>

5. MainActivity 中调用

? 5.1 MainActivty.java

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainerView);
        NavController controller = navHostFragment.getNavController();
        NavigationUI.setupActionBarWithNavController(this, controller);
    }

    @Override
    public boolean onSupportNavigateUp() {
        NavHostFragment navHostFragment = (NavHostFragment) getSupportFragmentManager().findFragmentById(R.id.fragmentContainerView);
        NavController controller = navHostFragment.getNavController();
        return controller.navigateUp();
    }
}

? 5.2 activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <androidx.fragment.app.FragmentContainerView
        android:id="@+id/fragmentContainerView"
        android:name="androidx.navigation.fragment.NavHostFragment"
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        app:defaultNavHost="true"
        app:navGraph="@navigation/my_navigation" />
</androidx.constraintlayout.widget.ConstraintLayout>

6. 效果图

? ?