2月4日

今天主要研究了安卓系统关于如何保持后台运行的相关方面。

package com.eb.myapplicationsd;

import androidx.appcompat.app.AppCompatActivity;

import androidx.databinding.DataBindingUtil;

import androidx.lifecycle.SavedStateViewModelFactory;

import androidx.lifecycle.ViewModelProvider;

import androidx.lifecycle.ViewModelProviders;

import android.os.Bundle;

import com.eb.myapplicationsd.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 = ViewModelProviders.of(this, new SavedStateViewModelFactory(getApplication(),this)).get(MyViewModel.class);

         binding.setData(myViewModel);

         binding.setLifecycleOwner(this);}

 

    @Override

    protected void onPause() {

        super.onPause();

        myViewModel.save();}}

 

 

package com.eb.myapplicationsd;

 

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;

import androidx.lifecycle.ViewModel;

 

public class MyViewModel extends AndroidViewModel {

    SavedStateHandle savedStateHandle;

    String key=getApplication().getResources().getString(R.string.data_key);

    String shpname=getApplication().getResources().getString(R.string.shp_name);

    public MyViewModel(@NonNull Application application,SavedStateHandle savedStateHandle) {

        super(application);

        this.savedStateHandle=savedStateHandle;

        if(!savedStateHandle.contains(key))

        {}}

  public  LiveData<Integer>getNumber(){

        return savedStateHandle.getLiveData(key);}

    public void load(){

        SharedPreferences sharedPreferences=getApplication().getSharedPreferences(shpname, Context.MODE_PRIVATE);

        int x=sharedPreferences.getInt(key,0);

        savedStateHandle.set(key,x);}

    public void save(){

        SharedPreferences sharedPreferences=getApplication().getSharedPreferences(shpname,Context.MODE_PRIVATE);

        SharedPreferences.Editor editor=sharedPreferences.edit();

        editor.putInt(key,getNumber().getValue());

        editor.apply();}

    public void add(int x){

        savedStateHandle.set(key,getNumber().getValue()+x);}}