通过ViewModel实现的数据共享符合Android的MVC设计模式，将数据独立出来

实现的Demo

1、主页面通过SeekBar 来改变数字的值

2、点击进入就进入第二个界面，但是数据还是共享的

3、随便加两个数字上去，再次切换

4、发现数据还是共享的

下面是具体实现步骤：

1、建立两个Fragment（使用了Binding 和 Navigation）

一点要添加Binding 和 Navigation 不然做不了

2、建立一个继承于ViewModel的类

3、分别在两个Fragment的代码中使用继承于ViewModel的那个类，就可以实现数据共享

下面是具体代码：

1、继承于ViewModel的类

package com.example.naviation01;import androidx.lifecycle.MutableLiveData;import androidx.lifecycle.ViewModel;public class MyViewMode extends ViewModel { private MutableLiveData<Integer> number; public MutableLiveData<Integer> getNumber(){ if(this.number == null){ this.number = new MutableLiveData<>(); this.number.setValue(0); } return this.number; } public void add(int x){ this.number.setValue(this.number.getValue()+x); if(this.number.getValue() < 0){ this.number.setValue(0); } }}

2、Fragment 主页

package com.example.naviation01;import android.os.Bundle;import androidx.databinding.DataBindingUtil;import androidx.fragment.app.Fragment;import androidx.fragment.app.FragmentController;import androidx.lifecycle.ViewModel;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 com.example.naviation01.databinding.FragmentHomeBinding;/** * A simple {@link Fragment} subclass. */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 final MyViewMode myViewMode; myViewMode = ViewModelProviders.of(getActivity()).get(MyViewMode.class); FragmentHomeBinding binding; binding = DataBindingUtil.inflate(inflater,R.layout.fragment_home,container,false); binding.setData(myViewMode); binding.setLifecycleOwner(getActivity()); binding.seekBar.setProgress(myViewMode.getNumber().getValue()); binding.seekBar.setOnSeekBarChangeListener(new SeekBar.OnSeekBarChangeListener() { @Override public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) { myViewMode.getNumber().setValue(progress); } @Override public void onStartTrackingTouch(SeekBar seekBar) { } @Override public void onStopTrackingTouch(SeekBar seekBar) { } }); binding.button.setOnClickListener(new View.OnClickListener() { @Override public void onClick(View v) { NavController controller = Navigation.findNavController(v); controller.navigate(R.id.action_homeFragment_to_detailFragment); } }); return binding.getRoot(); //return inflater.inflate(R.layout.fragment_home, container, false); }}

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.naviation01.MyViewMode" /> </data> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".HomeFragment"> <androidx.constraintlayout.widget.ConstraintLayout android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:id="@+id/textView" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginStart="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" 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="0.255" /> <SeekBar android:id="@+id/seekBar" android:layout_width="0dp" android:layout_height="wrap_content" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" 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="0.456" /> <Button android:id="@+id/button" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" android:text="@string/function01" 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="0.679" /> </androidx.constraintlayout.widget.ConstraintLayout> </FrameLayout></layout>

3、Fragment 副页

package com.example.naviation01;import android.os.Bundle;import androidx.databinding.DataBindingUtil;import androidx.fragment.app.Fragment;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 com.example.naviation01.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) { // Inflate the layout for this fragment MyViewMode myViewMode; myViewMode = ViewModelProviders.of(getActivity()).get(MyViewMode.class); FragmentDetailBinding binding; binding = DataBindingUtil.inflate(inflater,R.layout.fragment_detail,container,false); binding.setDate(myViewMode); 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_homeFragment); } }); return binding.getRoot(); //return inflater.inflate(R.layout.fragment_detail, container, false); }}

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="date" type="com.example.naviation01.MyViewMode" /> </data> <FrameLayout android:layout_width="match_parent" android:layout_height="match_parent" tools:context=".DetailFragment"> <androidx.constraintlayout.widget.ConstraintLayout android:layout_width="match_parent" android:layout_height="match_parent"> <TextView android:id="@+id/textView3" android:layout_width="131dp" android:layout_height="55dp" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" android:text="@{String.valueOf(date.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="0.23" /> <Button android:id="@+id/button2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" android:text="@string/function02" android:onClick="@{()->date.add(1)}" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.104" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" app:layout_constraintVertical_bias="0.499" /> <Button android:id="@+id/button3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" android:text="@string/function03" android:onClick="@{()->date.add(-1)}" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintHorizontal_bias="0.899" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" app:layout_constraintVertical_bias="0.499" /> <Button android:id="@+id/button4" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_marginStart="8dp" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" android:text="@string/function04" 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="0.664" /> </androidx.constraintlayout.widget.ConstraintLayout> </FrameLayout></layout>

4、xml Main_Activity

<?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"> <fragment android:id="@+id/fragment" android:name="androidx.navigation.fragment.NavHostFragment" android:layout_width="match_parent" android:layout_height="match_parent" android:layout_marginTop="8dp" android:layout_marginEnd="8dp" android:layout_marginBottom="8dp" app:defaultNavHost="true" app:layout_constraintBottom_toBottomOf="parent" app:layout_constraintEnd_toEndOf="parent" app:layout_constraintStart_toStartOf="parent" app:layout_constraintTop_toTopOf="parent" app:navGraph="@navigation/nav_graph" /></androidx.constraintlayout.widget.ConstraintLayout>

总结

以上所述是小编给大家介绍的Android通过ViewModel保存数据实现多页面的数据共享功能，希望对大家有所帮助，如果大家有任何疑问请给我留言，小编会及时回复大家的。在此也非常感谢大家对网站的支持！
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