详解Android MVVM模式使用

前言:

MVVM是Model-View-ViewModel的简写。它本质上就是MVC 的改进版。MVVM 就是将其中的View 的状态和行为抽象化，让我们将视图 UI 和业务逻辑分开。当然这些事 ViewModel 已经帮我们做了，它可以取出 Model 的数据同时帮忙处理 View 中由于需要展示内容而涉及的业务逻辑

工程目录结构:

使用步骤:

1.在项目app的Build下添加:

apply plugin: 'com.android.application' android { compileSdkVersion 26 buildToolsVersion "27.0.3" dataBinding{ enabled true } ....... }

2.BaseObservable数据绑定，新建一个JavaBean：

public class Student extends BaseObservable { private String name; private String age; private String header; public String getHeader() { return header; } public void setHeader(String header) { this.header = header; } public Student(String header, String name, String age) { this.name = name; this.age = age; this.header = header; } @Bindable public String getName() { return name; } public void setName(String name) { this.name = name; notifyPropertyChanged(com.example.mvvm.BR.name); } @Bindable public String getAge() { return age; } public void setAge(String age) { this.age = age; notifyPropertyChanged(com.example.mvvm.BR.age); } /** * 自定义属性:提供一个静态方法来加载image * * @param view * @param url */ @BindingAdapter("bind:header") public static void getImage(ImageView view, String url) { Picasso.with(view.getContext()).load(url).into(view); } public void click(View view) { Toast.makeText(view.getContext(), getName(), Toast.LENGTH_SHORT).show(); } }

3.创建CommAdapter适配器

public class CommAdapter<T> extends BaseAdapter { private Context context; private LayoutInflater inflater; private int layoutId; /** * variable的ID自动生成 */ private int variableId; private List<T> list; public CommAdapter(Context context, LayoutInflater inflater, int layoutId, int variableId, List<T> list) { this.context = context; this.inflater = inflater; this.layoutId = layoutId; this.variableId = variableId; this.list = list; } @Override public int getCount() { return list.size(); } @Override public Object getItem(int position) { return list.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { ViewDataBinding dataBinding; if(convertView==null){ dataBinding= DataBindingUtil.inflate(inflater,layoutId,parent,false); }else{ /** * 重用之前的convertView */ dataBinding=DataBindingUtil.getBinding(convertView); } dataBinding.setVariable(variableId,list.get(position)); return dataBinding.getRoot().getRootView(); } }  note: variableId 编译自动生成，如下：

4.item_pattern.xml数据绑定

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"> <data> <variable name="student" type="com.example.mvvm.Student" /> data> <LinearLayout android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <ImageView android:layout_width="150dp" android:layout_height="100dp" app:header="@{student.header}" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:gravity="center" android:text="@{student.name}" /> <TextView android:layout_width="wrap_content" android:layout_height="wrap_content" android:gravity="center" android:onClick="@{student.click}" android:text="@{student.age}" /> LinearLayout> layout>

5.MainActivity测试调用

public class MainActivity extends AppCompatActivity { ListView list; List<Student> data=new ArrayList<>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); list= (ListView) findViewById(R.id.listView); data.add(new Student("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1528871063802&di=9e8faa6eb45eccc8f678be6797159a71&imgtype=0&src=http%3A%2F%2Fimgsrc.baidu.com%2Fimgad%2Fpic%2Fitem%2F9d82d158ccbf6c8154bdd5ccb63eb13533fa4008.jpg","1","1")); data.add(new Student("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1528871063802&di=9e8faa6eb45eccc8f678be6797159a71&imgtype=0&src=http%3A%2F%2Fimgsrc.baidu.com%2Fimgad%2Fpic%2Fitem%2F9d82d158ccbf6c8154bdd5ccb63eb13533fa4008.jpg","2","2")); data.add(new Student("https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1528871063802&di=9e8faa6eb45eccc8f678be6797159a71&imgtype=0&src=http%3A%2F%2Fimgsrc.baidu.com%2Fimgad%2Fpic%2Fitem%2F9d82d158ccbf6c8154bdd5ccb63eb13533fa4008.jpg","3","3")); list.setAdapter(new CommAdapter<Student>(this,getLayoutInflater(),R.layout.item_pattern, BR.student,data)); } }

运行效果: