Android中ViewModel的使用方法。这个是作为视图和数据的桥梁。保持数据通信

1.添加依赖

implementation "androidx.lifecycle:lifecycle-viewmodel:2.2.0"

2.创建MyViewModel

import androidx.lifecycle.ViewModel;

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

3.在Activity中使用。

import androidx.appcompat.app.AppCompatActivity;
import androidx.databinding.DataBindingUtil;
import androidx.lifecycle.ViewModelProvider;
import android.os.Bundle;
import android.view.View;
import com.cdc.viewmodel.databinding.ActivityMainBinding;
public class MainActivity extends AppCompatActivity {
    
    
    private ActivityMainBinding mBinding;
    private MyViewModel myViewModel;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
    
    
        super.onCreate(savedInstanceState);
        mBinding=DataBindingUtil.setContentView(this,R.layout.activity_main);
//如果继承的是AndroidViewModel,则这里使用以下的方法获取ViewModel的实例:
//wordViewModel=new ViewModelProvider.AndroidViewModelFactory
//(this.getApplication()).create(WordViewModel.class);
        myViewModel=new ViewModelProvider(this).get(MyViewModel.class);
        mBinding.textView.setText(String.valueOf(myViewModel.number));
        mBinding.button1.setOnClickListener(new View.OnClickListener() {
    
    
            @Override
            public void onClick(View view) {
    
    
                myViewModel.number++;
                mBinding.textView.setText(String.valueOf(myViewModel.number));
            }
        });
        mBinding.button2.setOnClickListener(new View.OnClickListener() {
    
    
            @Override
            public void onClick(View view) {
    
    
                myViewModel.number+=2;
                mBinding.textView.setText(String.valueOf(myViewModel.number));
            }
        });
    }
}

4.效果。旋转屏幕页面中TextView的数值不会归零