AndroidViewModel是ViewModel的一个子类，可以直接调用getApplication()，由此可以访问应用的全局资源

结合SharedPreferences实现保存数据

MainActivity.java

package com.tjjingpan.study.viewmodelshp;

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.SavedStateViewModelFactory;

import android.os.Bundle;

import com.tjjingpan.study.viewmodelshp.databinding.ActivityMainBinding;

public class MainActivity extends AppCompatActivity {
    MyViewModel myViewModel;
    ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //setContentView(R.layout.activity_main);
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        //myViewModel = new MyViewModel();
        //myViewModel.application= getApplication();
        //myViewModel.context = getApplicationContext();

        SavedStateViewModelFactory savedStateViewModelFactory = new SavedStateViewModelFactory(getApplication(), this);
        myViewModel = savedStateViewModelFactory.create(MyViewModel.class);

        binding.setData(myViewModel);
        binding.setLifecycleOwner(this);
    }

    @Override
    protected void onPause() {
        super.onPause();
        myViewModel.save();
    }
}

MyViewModel.java

package com.tjjingpan.study.viewmodelshp;

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.SavedStateHandle;

public class MyViewModel extends AndroidViewModel {
    private SavedStateHandle handle;
    private String key = getApplication().getResources().getString(R.string.data_key);
    private String shpName = getApplication().getResources().getString(R.string.shp_name);

    public MyViewModel(@NonNull Application application, SavedStateHandle handle) {
        super(application);
        this.handle = handle;
        //判断handle是否存在需要的数据，不存在，从SharedPreferences加载
        if (!handle.contains(key)) {
            load();
        }
    }

    public LiveData 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() == null ? 0 : getNumber().getValue());
        editor.apply();
    }


    public void add(int x) {
        handle.set(key, getNumber().getValue() == null ? 0 : getNumber().getValue() + x);
        //save();
    }
    //Application application;
//    Context context;
//
//    void foo(){
//    }
}

布局文件

构建文件

plugins {
    id 'com.android.application'
}

android {
    namespace 'com.tjjingpan.study.viewmodelshp'
    compileSdk 33

    defaultConfig {
        applicationId "com.tjjingpan.study.viewmodelshp"
        minSdk 23
        targetSdk 33
        versionCode 1
        versionName "1.0"

        testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"
        dataBinding.enabled = true
    }

    buildTypes {
        release {
            minifyEnabled false
            proguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'
        }
    }
    compileOptions {
        sourceCompatibility JavaVersion.VERSION_1_8
        targetCompatibility JavaVersion.VERSION_1_8
    }
}

dependencies {

    implementation 'androidx.appcompat:appcompat:1.2.0'
    implementation 'com.google.android.material:material:1.3.0'
    implementation 'androidx.constraintlayout:constraintlayout:2.0.4'
    implementation 'androidx.lifecycle:lifecycle-viewmodel-savedstate:2.3.1'
    testImplementation 'junit:junit:4.+'
    androidTestImplementation 'androidx.test.ext:junit:1.1.2'
    androidTestImplementation 'androidx.test.espresso:espresso-core:3.3.0'
}