Android实现关机后数据不会丢失问题_Android

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

Android实现关机后数据不会丢失问题

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

Android实现关机后数据不会丢失问题

数据类

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									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>