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;@Overrideprotected 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);}@Overrideprotected 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<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() == 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

<?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><variablename="data"type="com.tjjingpan.study.viewmodelshp.MyViewModel" /></data><androidx.constraintlayout.widget.ConstraintLayoutandroid:layout_width="match_parent"android:layout_height="match_parent"tools:context=".MainActivity"><TextViewandroid:id="@+id/textView"android:layout_width="wrap_content"android:layout_height="wrap_content"android:text="@{String.valueOf(data.getNumber())}"android:textSize="34sp"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintHorizontal_bias="0.498"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent"app:layout_constraintVertical_bias="0.07999998"/><Buttonandroid:id="@+id/button"android:layout_width="wrap_content"android:layout_height="wrap_content"android:onClick="@{()-> data.add(1)}"android:text="@string/button_plus"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintHorizontal_bias="0.241"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent" /><Buttonandroid:id="@+id/button2"android:layout_width="wrap_content"android:layout_height="wrap_content"android:onClick="@{()-> data.add(-1)}"android:text="@string/button_minute"app:layout_constraintBottom_toBottomOf="parent"app:layout_constraintEnd_toEndOf="parent"app:layout_constraintHorizontal_bias="0.678"app:layout_constraintStart_toStartOf="parent"app:layout_constraintTop_toTopOf="parent" /></androidx.constraintlayout.widget.ConstraintLayout>
</layout>

构建文件

plugins {id 'com.android.application'
}android {namespace 'com.tjjingpan.study.viewmodelshp'compileSdk 33defaultConfig {applicationId "com.tjjingpan.study.viewmodelshp"minSdk 23targetSdk 33versionCode 1versionName "1.0"testInstrumentationRunner "androidx.test.runner.AndroidJUnitRunner"dataBinding.enabled = true}buildTypes {release {minifyEnabled falseproguardFiles getDefaultProguardFile('proguard-android-optimize.txt'), 'proguard-rules.pro'}}compileOptions {sourceCompatibility JavaVersion.VERSION_1_8targetCompatibility 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'
}