Android实现关机后数据不会丢失问题

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,网站的支持！
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来源：https://blog.csdn.net/weixin_43635647/article/details/102766005