要实现关机后数据也不会丢失，需要使用到 Androidviewmodel,SaveStateHandle 和 SharePreferences 要达到的目的就是将数据保存成这个亚子

就不会出现app在异常闪退或者关机后数据的丢失了注意在使用SaveStateHandle和binding的时候需要在gradle里面设置一波

数据类

package com.example.applicationtest04;

import android.app.Application;
import android.content.Context;
import android.content.SharedPreferences;

import androidx.annotation.NonNull;
import androidx.lifecycle.Androidviewmodel;
import androidx.lifecycle.LiveData;
import androidx.lifecycle.MutableLiveData;
import androidx.lifecycle.SavedStateHandle;

public class Myviewmodel extends Androidviewmodel {
 SavedStateHandle handle; //声明savedstatehandle 类型
 String shpName = getApplication().getResources().getString(R.string.shp_name);
 String key = getApplication().getResources().getString(R.string.key);
 public Myviewmodel(@NonNull Application application,SavedStateHandle handle) {
  super(application);
  this.handle = handle;
  if(!handle.contains(key)){
   load();
  }
 }
 public LiveData<Integer> getNumber(){
  return handle.getLiveData(key);
 }
 public void load(){
  SharedPreferences shp = getApplication().getSharedPreferences(shpName,Context.MODE_PRIVATE);
  int x = shp.getInt(key,0);
  handle.set(key,x);

 }
 public void save(){
  SharedPreferences shp = getApplication().getSharedPreferences(shpName,Context.MODE_PRIVATE);
  SharedPreferences.Editor editor = shp.edit();
  editor.putInt(key,getNumber().getValue());
  editor.apply();
 }
 public void add(int x){
  handle.set(key,getNumber().getValue()+x);
 }
}
//这段代码里面有几个重要的点就是在使用handle的时候要注意使用的数据是liveData

Mainactive类

package com.example.applicationtest04;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.SavedStateVMFactory;
import androidx.lifecycle.viewmodelProvider;
import androidx.lifecycle.viewmodelProviders;

import android.os.Bundle;

import com.example.applicationtest04.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {
 Myviewmodel myviewmodel;
 ActivityMainBinding binding;
 @Override
 protected void onCreate(Bundle savedInstanceState) {
  super.onCreate(savedInstanceState);
  binding = DataBindingUtil.setContentView(this,R.layout.activity_main);
  this.myviewmodel = viewmodelProviders.of(this,new SavedStateVMFactory(this)).get(Myviewmodel.class);
  binding.setData(myviewmodel);
  binding.setLifecycleOwner(this);
 }

 @Override
 protected void onPause() {
  super.onPause();
  myviewmodel.save();
 }
}
//这段代码的重点就是使用onPause这个声明周期的函数来调用save()函数

布局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.applicationtest04.Myviewmodel" />
 </data>
 <androidx.constraintlayout.widget.ConstraintLayout
  android:layout_width="match_parent"
  android:layout_height="match_parent"
  tools:context=".MainActivity">
  <TextView
   android:layout_width="wrap_content"
   android:layout_height="wrap_content"
   android:text="@{String.valueOf(Data.getNumber())}"
   android:textColor="@color/colorPrimaryDark"
   android:textSize="36sp"
   app:layout_constraintBottom_toBottomOf="parent"
   app:layout_constraintHorizontal_bias="0.497"
   app:layout_constraintLeft_toLeftOf="parent"
   app:layout_constraintRight_toRightOf="parent"
   app:layout_constraintTop_toTopOf="parent"
   app:layout_constraintVertical_bias="0.324" />
  <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/buttonPlus"
   android:onClick="@{()->Data.add(1)}"
   app:layout_constraintBottom_toBottomOf="parent"
   app:layout_constraintEnd_toEndOf="parent"
   app:layout_constraintHorizontal_bias="0.182"
   app:layout_constraintStart_toStartOf="parent"
   app:layout_constraintTop_toTopOf="parent"
   app:layout_constraintVertical_bias="0.499" />
  <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/buttonSub"
   android:onClick="@{()->Data.add(-1)}"
   app:layout_constraintBottom_toBottomOf="parent"
   app:layout_constraintEnd_toEndOf="parent"
   app:layout_constraintHorizontal_bias="0.804"
   app:layout_constraintStart_toStartOf="parent"
   app:layout_constraintTop_toTopOf="parent"
   app:layout_constraintVertical_bias="0.499" />
 </androidx.constraintlayout.widget.ConstraintLayout>
</layout>

测试效果先加到12

再重启

重启之后重新打开app

值还是没有变化测试成功

总结

以上所述是小编给大家介绍的Android实现关机后数据不会丢失问题,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我们网站的支持！
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