ViewModel在Android Studio 新版本中初始化的方法

核心初始化语句：

​
myViewModel = new ViewModelProvider(this, new ViewModelProvider.NewInstanceFactory()).get(MyViewModel.class);

​

例子项目：简易篮球计分器

实现如下：

实现步骤：

1.创建一个java类，继承ViewModel，并将number声明为全局变量。

MyViewModel.java

package com.example.viewmodeltest;

import android.arch.lifecycle.ViewModel;

public class MyViewModel extends ViewModel {
    public int number = 0;
}

2.进行UI界面设置，将ViewModel初始化，用以保存数据。

MainActivity.java

package com.example.viewmodeltest;

import android.arch.lifecycle.ViewModelProvider;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    MyViewModel myViewModel;
    TextView textView;
    Button button1, button2, button3;
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        myViewModel = new ViewModelProvider(this, new ViewModelProvider.NewInstanceFactory()).get(MyViewModel.class);

        textView = findViewById(R.id.textView);
        textView.setText(String.valueOf(myViewModel.number));

        button1 = findViewById(R.id.button);
        button2 = findViewById(R.id.button2);
        button3 = findViewById(R.id.button3);

        button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myViewModel.number++;
                textView.setText(String.valueOf(myViewModel.number));
            }
        });

        button2.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myViewModel.number += 2;
                textView.setText(String.valueOf(myViewModel.number));
            }
        });

        button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                myViewModel.number += 3;
                textView.setText(String.valueOf(myViewModel.number));
            }
        });

    }
}

其他：

activity_main.xml

strings.xml

    ViewModelTest
    Welcome
    +1
    +2
    +3

AndroidManifest.xml