Android通过ViewModel保存数据实现多页面的数据共享功能
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
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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 MutableLiveDatanumber; public MutableLiveData 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"?>
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"?>
4、xml Main_Activity
<?xml version="1.0" encoding="utf-8"?>
总结
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