安卓mvvm框架helloworld

安卓MVVM框架的HelloWorld可以通过以下步骤实现：

1. 在build.gradle文件中添加以下依赖项：

dependencies {
    def lifecycle_version = "2.2.0"
    implementation "androidx.lifecycle:lifecycle-viewmodel:$lifecycle_version"
    implementation "androidx.lifecycle:lifecycle-livedata:$lifecycle_version"
    implementation "androidx.lifecycle:lifecycle-common-java8:$lifecycle_version"
    implementation 'com.google.android.material:material:1.2.1'
}

2. 创建一个ViewModel类，该类将处理与UI无关的数据逻辑。例如：

import androidx.lifecycle.ViewModel;

public class MyViewModel extends ViewModel {
    private int count = 0;

    public int getCount() {
        return count;
    }

    public void setCount(int count) {
        this.count = count;
    }

    public void incrementCount() {
        count++;
    }
}

3. 创建一个Activity或Fragment类，该类将处理UI逻辑。例如：

import androidx.appcompat.app.AppCompatActivity;
import androidx.lifecycle.ViewModelProvider;

import android.os.Bundle;
import android.view.View;
import android.widget.TextView;

public class MainActivity extends AppCompatActivity {
    private MyViewModel viewModel;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        viewModel = new ViewModelProvider(this).get(MyViewModel.class);

        final TextView countTextView = findViewById(R.id.count_text_view);
        countTextView.setText(String.valueOf(viewModel.getCount()));

        findViewById(R.id.increment_button).setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                viewModel.incrementCount();
                countTextView.setText(String.valueOf(viewModel.getCount()));
            }
        });
    }
}

4. 创建一个布局文件，该文件将定义UI元素。例如：

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:orientation="vertical"
    android:layout_width="match_parent"
    android:layout_height="match_parent">

    <TextView
        android:id="@+id/count_text_view"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:textSize="24sp"
        android:text="0"
        android:layout_gravity="center_horizontal"/>

    <Button
        android:id="@+id/increment_button"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="Increment"
        android:layout_gravity="center_horizontal"/>

</LinearLayout>