浅谈android MVVM 让你的代码更简洁

最近项目需要开始研究MVVM 以前是万年MVC 千年MVP 呵呵闷骚程序猿自我舒缓

好刚开始研究
MVVM是将“数据模型数据双向绑定”的思想作为核心，因此在View和Model之间没有联系，通过ViewModel进行交互，而且Model和ViewModel之间的交互是双向的，因此视图的数据的变化会同时修改数据源，而数据源数据的变化也会立即反应到View上。

M 即model 模型
V 即View 视图
VM 即ViewModel 视图模型
　MVVM模式是Model-View-ViewMode模式的简称。由视图(View)、视图模型(ViewModel)、模型(Model)三部分组成。通过这三部分实现UI逻辑、呈现逻辑和状态控制、数据与业务逻辑的分离。
　当然也有很多好处低耦合细分工简介高效
好今天就说一下 MVVM绑定数据
第一步准备工作
在app的build.gradle文件里 android{}里添加
dataBinding {
enabled = true
}

到此准备工作结束非常简单
第二步模型例如这样今天绑定数据 textview imgeview 以及刷新
1 textview 非常简单使用了以后你绝对不会在想mvc的 findViewById();
我要显示名字和年龄还有性别
student 数据类
private String name;
private String sex;
private String age;
// 构造方法
public Student(String name, String sex, String age) {
this.name = name;
this.sex = sex;
this.age = age;
}
setget方法自己写此处就不多说了
mvc 中我们都是以几个布局控件作为根节点 mvvm 中要用layout 作为根节点同时引用data 标签添加数据类
data/
/ variable/
name=”student”
type=”com.sxm.mvvmdemo.viewbeans.Student”
/variable/
/data
LinearLayout
android:layout_width=”match_parent”
android:layout_height=”match_parent”
android:orientation=”vertical”>
TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_gravity=”center”
android:textSize=”20sp”
android:textColor=”#ec4729”
android:text=”@{student.name}”
TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_gravity=”center”
android:textSize=”15sp”
android:textColor=”#434542”
android:text=”@{student.sex}”
TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_gravity=”center”
android:textSize=”10sp”
android:textColor=”#5ed427”
android:text=”@{student.age}”
LinearLayout>
好布局完成 activity中给数据类赋值
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
final ActivityMainBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
Student student = new Student(“孙中山”,”男”,”45”);
binding.setStudent(student)
}
运行一下就可以显示了
2 点击事件
variable
name=”onclick”
type=”android.view.View.OnClickListener”/variable>
TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_gravity=”center”
android:textSize=”20sp”
android:onClick=”@{onclick}”
android:clickable=”true”
android:id=”@+id/name”
android:text=”@{student.name}”/>
binding.setOnclick(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this, “点击了”, Toast.LENGTH_SHORT).show();
}
});
也可以添加id 进行添加点击事件可以直接找到这个控件
binding.name.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
Toast.makeText(MainActivity.this, “又点击了”, Toast.LENGTH_SHORT).show();
}
});
3 绑定图片
// 图片数据类
public class ImgView extends BaseObservable {
int picid;
@Bindable
public int getPicid() {
return picid;
}

public void setPicid(int picid) {
    this.picid = picid;
    notifyPropertyChanged(BR.picid);
}
@BindingAdapter("android:src")
public static void setPic(ImageView img,int picid){
    img.setImageResource(picid);
}

}
data>
import type=”com.sxm.mvvmdemo.viewbeans.ImgView”>/import>
data>
这次我们使用导入的方式比 / variable/ 还要简洁
ImageView
android:id=”@+id/two_img”
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:scaleType=”centerInside”
android:clickable=”true”
android:onClick=”@{onclickImg}”
android:layout_gravity=”center”
android:src=”@{imgview.picid}”/>
同上
final ActivityTwoBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_two);
final ImgView imgView = new ImgView();
imgView.setPicid(R.drawable.mj12);
binding.setImgview(imgView);
运行一下就可以了
你也可以给他们添加点击事件同上一样道理
4 给listview绑定数据
ListView
android:layout_width=”match_parent”
android:layout_height=”match_parent”
android:scrollbars=”none”
android:id=”@+id/view_list”>/ListView>
给一个list view
listview = (ListView) findViewById(R.id.view_list);
给数据
lists = new ArrayList<>();
for (int i = 0; i < 20; i++) {
ListBean listBean = new ListBean();
listBean.setAge(“17”);
listBean.setImgurl(R.drawable.mj12);//图片
listBean.setName(“黄渤”);
lists.add(listBean);
}
重点是listview的item
ListBean 数据类
public class ListBean extends BaseObservable {
// 刷新用
ObservableField /String> name = new ObservableField<>();
ObservableField / Integer> imgurl = new ObservableField<>();
ObservableField /String> age = new ObservableField<>();

public ListBean() {
}

public ListBean(int imgurl, String name, String age) {
    this.name.set(name);
    this.age.set(age);
    this.imgurl.set(imgurl);
}
//条目点击事件
public void onClickItem(View v){
    Toast.makeText(v.getContext(), "点击了", Toast.LENGTH_SHORT).show();
}

@Bindable
public int getImgurl() {
    return imgurl.get();
}

public void setImgurl(int imgurl) {
    this.imgurl.set(imgurl);
        notifyPropertyChanged(BR.imgurl);
}
// 设置图片
@BindingAdapter("android:src")
public static void setImg(ImageView img, int imgurl){
    img.setImageResource(imgurl);
}

public String getName() {
    return name.get();
}

public void setName(String name) {
    this.name.set(name);
}

public String getAge() {
    return age.get();
}

public void setAge(String age) {
    this.age.set(age);
}

}
item xml

?xml version=”1.0” encoding=”utf-8”?>
layout xmlns:android=”http://schemas.android.com/apk/res/android”>
data>

  variable
      name="listban"
      type="com.sxm.mvvmdemo.viewbeans.ListBean">/variable>

/data>
RelativeLayout
android:onClick=”@{listban.onClickItem}”
android:gravity=”center_vertical”
android:layout_width=”match_parent”
android:layout_height=”wrap_content”>
ImageView
android:layout_width=”80dp”
android:layout_height=”80dp”
android:scaleType=”centerInside”
android:id=”@+id/item_headimg”
android:src=”@{listban.imgurl}”/>
TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:layout_toRightOf=”@+id/item_headimg”
android:layout_alignTop=”@+id/item_headimg”
android:layout_marginLeft=”3dp”
android:textSize=”15sp”
android:textColor=”#fa0d64”
android:id=”@+id/item_name”
android:text=”@{listban.name}”/>
TextView
android:layout_width=”wrap_content”
android:layout_height=”wrap_content”
android:text=”@{listban.age}”
android:layout_toRightOf=”@+id/item_headimg”
android:layout_below=”@+id/item_name”
android:layout_marginTop=”3dp”
android:textSize=”13sp”
android:id=”@+id/item_age”
android:layout_marginLeft=”3dp”/>
/RelativeLayout>
/layout>

万能adapter

public class MyListviewAdapter /T> extends BaseAdapter {
private Context context;
private List /T> list;
private int layoutId;
private int variableId;
LayoutInflater inflate;

public MyListviewAdapter(Context context, List /T> list, int layoutId, int variableId) {
    this.context = context;
    this.list = list;
    this.layoutId = layoutId;
    this.variableId = variableId;
    inflate = LayoutInflater.from(context);
}

@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 binding;
    if (convertView==null){
        binding = DataBindingUtil.inflate(inflate,layoutId,parent,false);

    }else {
        binding= DataBindingUtil.getBinding(convertView);
    }
    binding.setVariable(variableId,list.get(position));
    return binding.getRoot();
}

}

activity

public class ListViewActivity extends Activity {

private ListView listview;
private List<ListBean> lists;
private MyListviewAdapter<ListBean> adapter;
private Handler handler = new Handler(){
    @Override

    public void handleMessage(Message msg) {
        super.handleMessage(msg);
        switch (msg.what){
            case 1:
                Toast.makeText(ListViewActivity.this, "接受了信息", Toast.LENGTH_SHORT).show();
                if (adapter.getCount()==20){
                    for (int i = 0; i < 40; i++) {
                        ListBean listBean = new ListBean();
                        listBean.setAge("18");
                        listBean.setImgurl(R.drawable.mj12);
                        listBean.setName("勃哥");
                        lists.add(listBean);
                    }
                }
                adapter.notifyDataSetChanged();
                break;
        }
    }
};

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_list_view);
    listview = (ListView) findViewById(R.id.view_list);
    initData();
    adapter = new MyListviewAdapter(ListViewActivity.this,lists, R.layout.list_item, BR.listban);

    listview.setAdapter(adapter);
    listview.setOnScrollListener(new AbsListView.OnScrollListener() {
        @Override
        public void onScrollStateChanged(AbsListView view, int scrollState) {
            Toast.makeText(ListViewActivity.this, "滑动状态变化", Toast.LENGTH_SHORT).show();
        }

        @Override
        public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) {
            Toast.makeText(ListViewActivity.this, "滑动中  "+visibleItemCount, Toast.LENGTH_SHORT).show();
            if (firstVisibleItem+visibleItemCount==totalItemCount&&totalItemCount>0){
                Toast.makeText(ListViewActivity.this, "到底了", Toast.LENGTH_SHORT).show();
               handler.sendEmptyMessage(1);
            }
        }
    });

}

private void initData() {
    lists = new ArrayList<>();
    for (int i = 0; i < 20; i++) {
        ListBean listBean = new ListBean();
        listBean.setAge("17");
        listBean.setImgurl(R.drawable.mj12);
        listBean.setName("黄渤");
        lists.add(listBean);
    }
}

}
到此就结束了 mvvm 继续研究后续发文

浅谈android MVVM 让你的代码更简洁

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