郑州app开发使用Navigation的小例子，也正是通过用Navigation来进行ViewModel的操作。下面是java代码：
MainActivity.java
package cn.xhhkj.cao;
import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.ViewModelProviders;
import android.os.Bundle;
public class MainActivity extends AppCompatActivity {
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
}
}
可以看出，基本没有变化。
MyViewModel.java
package cn.xhhkj.cao;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.ViewModel;
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);
}
}
}
这里就能看出，数据处理都在这里了。
MasterFragment.java
package cn.xhhkj.cao;
import android.os.Bundle;
import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelProviders;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import android.widget.SeekBar;
import cn.xhhkj.cao.databinding.FragmentMasterBinding;
/**
* A simple {@link Fragment} subclass.
*/
public class MasterFragment extends Fragment {
public MasterFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
final MyViewModel myViewModel;
myViewModel= ViewModelProviders.of(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();
}
}
DetailFragment.java
package cn.xhhkj.cao;
import android.os.Bundle;
import androidx.databinding.DataBindingUtil;
import androidx.fragment.app.Fragment;
import androidx.lifecycle.ViewModelProvider;
import androidx.lifecycle.ViewModelProviders;
import androidx.navigation.NavController;
import androidx.navigation.Navigation;
import android.view.LayoutInflater;
import android.view.View;
import android.view.ViewGroup;
import cn.xhhkj.cao.databinding.FragmentDetailBinding;
/**
* A simple {@link Fragment} subclass.
*/
public class DetailFragment extends Fragment {
public DetailFragment() {
// Required empty public constructor
}
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
MyViewModel myViewModel;
myViewModel= ViewModelProviders.of(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 controller= Navigation.findNavController(v);
controller.navigate(R.id.action_detailFragment_to_masterFragment);
}
});
return binding.getRoot();
// Inflate the layout for this fragment
//return inflater.inflate(R.layout.fragment_detail, container, false);
}
}
下面是布局代码
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"
android:orientation="vertical" android:layout_width="match_parent"
android:layout_height="match_parent"}
{fragment
android:id="@+id/fragment2"
android:name="androidx.navigation.fragment.NavHostFragment"
android:layout_width="match_parent"
android:layout_height="match_parent"
app:defaultNavHost="true"
app:navGraph="@navigation/nav" /}
{/androidx.constraintlayout.widget.ConstraintLayout}
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="cn.xhhkj.cao.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:maxLength="10"
android:text="@{String.valueOf(data.number)}"
android:textSize="30sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.538"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.255" /}
{SeekBar
android:id="@+id/seekBar"
android:layout_width="0dp"
android:layout_height="wrap_content"
android:max="30"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.0"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.431" /}
{Button
android:id="@+id/button"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_marginStart="132dp"
android:text="进入"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintHorizontal_bias="0.219"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.579" /}
{/androidx.constraintlayout.widget.ConstraintLayout}
{/layout}
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="cn.xhhkj.cao.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="30sp"
app:layout_constraintBottom_toBottomOf="parent"
app:layout_constraintEnd_toEndOf="parent"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.21" /}
{Button
android:id="@+id/button2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="+"
android:textSize="30sp"
android:onClick="@{()-}data.add(+1)}"
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"
app:layout_constraintVertical_bias="0.43" /}
{Button
android:id="@+id/button3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="-"
android:textSize="30sp"
android:onClick="@{()-}data.add(-1)}"
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"
app:layout_constraintVertical_bias="0.0" /}
{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_constraintHorizontal_bias="0.513"
app:layout_constraintStart_toStartOf="parent"
app:layout_constraintTop_toTopOf="parent"
app:layout_constraintVertical_bias="0.67" /}
{/androidx.constraintlayout.widget.ConstraintLayout}
{/layout}
以上就是全部代码了。
补充下，需要在gradle scripts这个文件夹里面build.gradle(module:app)这个文件里面添加这行代码
dataBinding {
enabled true
}
