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记录DataBinding使用

程序员文章站 2022-05-14 23:46:39
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例一

MainActivity

public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        User user = new User(this,"Test", "User",true);
        binding.setUser(user);
    }
}

User

public class User {
    public final String firstName;
    public final String lastName;
    public  Context context;
    public boolean isFriend;
    public User(Context context,String firstName, String lastName,boolean isFriend) {
        this.context=context;
        this.firstName = firstName;
        this.lastName = lastName;
        this.isFriend=isFriend;

    }
}

XML

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

    <data>

        <variable
            name="user"
            type="com.example.yaoyan.databinding.User" />
    </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:text="@{user.firstName}"/>
        <TextView android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{user.lastName}"/>
    </LinearLayout>
</layout>

记录DataBinding使用

例二 绑定事件

MainActivity

public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        User user = new User(this,"Test", "User",true);
        binding.setUser(user);
        binding.setHandlers(new MyHandlers());
    }
}

User类没变
XML

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="handlers"
            type="com.example.yaoyan.databinding.MyHandlers" />

        <variable
            name="user"
            type="com.example.yaoyan.databinding.User" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="@{user.isFriend ? handlers.onClickFriend : handlers.onClickEnemy}"
            android:text="@{user.firstName}" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:onClick="@{user.isFriend ? handlers.onClickEnemy : handlers.onClickFriend }"
            android:text="@{user.lastName}" />
    </LinearLayout>
</layout>

记录DataBinding使用

例三 导入类

<data>
     <import type="android.view.View"/>
</data>

<Button
    android:visibility="@{View.INVISIBLE}"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
 />

例四 List数组

MainActivity

public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        List<String> list=new ArrayList<>();
        list.add("aaa");
        binding.setUserList(list);
    }
}

XML

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

    <data>


        <import type="java.util.List" />

        <variable
            name="userList"
            type="List&lt;String>" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{userList[0].toLowerCase()}" />
    </LinearLayout>
</layout>

其中特别注意一点,在@{}表达式中不支持左括号,所以我们需要用转义字符代替左括号

例五 静态

public class Teacher {
    public static String   GG(){
       return "1111111";
    }
}

<data>
    <import type="com.example.yaoyan.databinding.Teacher"></import>
</data>
<Button
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:text="@{Teacher.GG()}" />

例六 变量

public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setUserList("尼玛");
    }
}
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">

    <data>
        <variable
            name="userList"
            type="String" />
    </data>
    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">
        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{userList}" />
    </LinearLayout>
</layout>

和 Java 一样，java.lang.* 会被自动导入。

例七 调用方法

public class User {
    public final String firstName;
    public final String lastName;
    public List<User> list=new ArrayList<User>();
    public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;

    }
    public  String  ggg(String st){
        System.out.println("st = " + st);
       return "asdas";
    }
}
public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setUserList(new User("111","222"));
    }
}
 <Button
    android:text='@{userList.ggg("123")}'
    android:textAllCaps="false"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" />
<data>
    <variable
        name="userList"
        type="com.example.yaoyan.databinding.User" />
</data>

例八 Context对象

public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setUserList(new User("111","222"));
    }
} 
public class User {
    public final String firstName;
    public final String lastName;
    public List<User> list=new ArrayList<User>();
    public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;

    }

    public  String  ggg(Context context){
        Toast.makeText(context,"toast",Toast.LENGTH_LONG).show();
        return "asdas";
    }
}
<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="userList"
            type="com.example.mac.studybinding.User" />
    </data>
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <Button
            android:text='@{userList.ggg(context)}'
            android:textAllCaps="false"
            android:layout_width="match_parent"
            android:layout_height="wrap_content" />
    </LinearLayout>
</layout>

binding 类会生成一个命名为context的特殊变量(其实就是 rootView 的 getContext())的返回值)，这个变量可用于表达式中. 如果有名为context的变量存在,那么生成的这个context特殊变量将被覆盖.

例九 可以在表达式中直接引用带id的view,引用时采用驼峰命名法.

<?xml version="1.0" encoding="utf-8"?>
<layout xmlns:android="http://schemas.android.com/apk/res/android">
    <data>
        <variable
            name="userList"
            type="com.example.mac.studybinding.User" />
        <import type="android.view.View"></import>
    </data>
    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <TextView
            android:id="@+id/yaoyan_name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:text="@{userList.firstName}" />

        <TextView
            android:text="@{userList.lastName}"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:visibility="@{yaoyanName.getVisibility() == View.GONE ? View.VISIBLE : View.GONE}" />


    </LinearLayout>
</layout>

这里TextView直接引用第一次TextView，yaoyanName为id的驼峰命名

public class MainActivity extends AppCompatActivity {
    private ActivityMainBinding binding;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        //会根据布局文件自动生成布局文件名开头的Binding类
        binding = DataBindingUtil.setContentView(this, R.layout.activity_main);
        binding.setUserList(new User("111","222"));
    }
}
public class User {
    public final String firstName;
    public final String lastName;
    public List<User> list=new ArrayList<User>();
    public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;

    }
    public  String  ggg(String st){
        System.out.println("st = " + st);
        return "asdas";
    }

    public  String  ggg(Context context){
        Toast.makeText(context,"toast",Toast.LENGTH_LONG).show();
        return "asdas";
    }
}

例十 RecyclerView+DataBinding

MainActivity

public class MainActivity extends AppCompatActivity {
    private RecyclerView mRecyclerView;
    private List<String> mDatas;
    private HomeAdapter mAdapter;

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

        initData();
        mRecyclerView = (RecyclerView) findViewById(R.id.id_recyclerview);
        mRecyclerView.setLayoutManager(new LinearLayoutManager(this));
        mRecyclerView.setAdapter(mAdapter = new HomeAdapter());

    }

    protected void initData()
    {
        mDatas = new ArrayList<String>();
        for (int i = 1; i < 100; i++)
        {
            mDatas.add("----" + i);
        }
    }

    class HomeAdapter extends RecyclerView.Adapter<HomeAdapter.MyViewHolder>
    {

        @Override
        public MyViewHolder onCreateViewHolder(ViewGroup parent, int viewType)
        {
            ViewDataBinding binding = DataBindingUtil.inflate(LayoutInflater.from(getApplicationContext()), R.layout.item_home, parent, false);
            MyViewHolder holder=new MyViewHolder(binding);
            return holder;
        }

        @Override
        public void onBindViewHolder(MyViewHolder holder, int position)
        {
            ItemHomeBinding binding = (ItemHomeBinding) holder.getBinding();
            String s = mDatas.get(position);
            Item item=new Item();
            item.setS(s);
            binding.setVariable(BR.obj, item);
            binding.executePendingBindings();
        }

        @Override
        public int getItemCount()
        {
            return mDatas.size();
        }

        class MyViewHolder extends RecyclerView.ViewHolder
        {
            private  ViewDataBinding binding;

            public MyViewHolder(ViewDataBinding  binding)
            {
                super(binding.getRoot());
                this.binding=binding;
            }

            public ViewDataBinding getBinding() {
                return binding;
            }
        }
    }
}

executePendingBindings()方法.这个方法迫使数据立即绑定而不是在下一帧的时候才绑定.RecyclerView会在onBindViewHolder方法执行后立即测量这些view.假设没使用executePendingBindings()方法,由于在下一帧的时候才会绑定,view就会绑定错误的data,测量也会出错.因此,executePendingBindings()是很重要的.

Item

public class Item {
    private String s;

    public String getS() {
        return s;
    }

    public void setS(String s) {
        this.s = s;
    }
}

Item_XML

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

    <data>
        <variable name="obj" type="com.example.mac.databinding.Item"/>
    </data>

<LinearLayout
    android:layout_width="match_parent"
    android:background="#44ff0000"
    android:layout_height="wrap_content">

    <TextView
        android:textColor="#000000"
        android:id="@+id/id_num"
        android:layout_width="match_parent"
        android:layout_height="50dp"
        android:gravity="center"
        android:text="@{obj.s}" />

</LinearLayout>
</layout>

Main_XML

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



    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <android.support.v7.widget.RecyclerView
            android:id="@+id/id_recyclerview"
            android:layout_width="match_parent"
            android:layout_height="match_parent"></android.support.v7.widget.RecyclerView>

    </LinearLayout>
</layout>

例十一 自动设置属性

public class MainActivity extends AppCompatActivity {
    private RecyclerView mRecyclerView;
    private List<String> mDatas;
    private HomeAdapter mAdapter;
    private ActivityMainBinding activityMainBinding;
    @Override
    protected void onCreate(Bundle savedInstanceState)
    {
        super.onCreate(savedInstanceState);
        activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);
    }
}
public class myView extends LinearLayout {
    public myView(Context context) {
        super(context);
    }

    public myView(Context context, @Nullable AttributeSet attrs) {
        super(context, attrs);
    }

    public myView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
    }

    public myView(Context context, @Nullable AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
    }

    // 自动 Setter
    public void setObject(String u) {
        System.out.println("myView.setObject");
    }
}
<?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">


    <LinearLayout
        android:orientation="vertical"
        android:layout_width="match_parent"
        android:layout_height="match_parent">

        <com.example.mac.databinding.myView
            android:id="@+id/aaa"
            <!--app:方法    实际是调用的setObject(String u) -->
            app:object='@{"123"}'
            android:layout_width="match_parent"
            android:layout_height="match_parent" />

    </LinearLayout>
</layout>

例十二 Observable

当表达式引用了一个类内的属性时，他会尝试直接调用域，getter，还有ObservableFields。

Observable 接口有一个添加/移除 listener 的机制，但通知取决于开发者。为了简化开发，我们创建了一个基类 BaseObservable，来实现 listener ***制。这个类也实现了域变动的通知，你只需要在 getter 上使用 Bindable 注解，并在 setter 中实现通知。
User

public class User  extends BaseObservable{
    public  String firstName;
    public  String lastName;
    public User(String firstName, String lastName) {
        this.firstName = firstName;
        this.lastName = lastName;

    }

    @Bindable
    public String getFirstName() {
        return this.firstName;
    }
    @Bindable
    public String getLastName() {
        return this.lastName;
    }
    public void setFirstName(String firstName) {
        this.firstName = firstName;
        notifyPropertyChanged(BR.firstName);
    }
    public void setLastName(String lastName) {
        this.lastName = lastName;
        notifyPropertyChanged(BR.lastName);
    }
}

MainActivity

public class MainActivity extends AppCompatActivity {
    private List<String> mDatas;
    private ActivityMainBinding activityMainBinding;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        activityMainBinding = DataBindingUtil.setContentView(this, R.layout.activity_main);

        User u=new User("123","456w");
        activityMainBinding.setUser(u);
    }

}

XML

<?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="user"
            type="com.example.yaoyan.databinding.User"></variable>

    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="vertical">

        <EditText
            android:id="@+id/et_1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text='@={user.firstName}' />

        <TextView
            android:id="@+id/et_2"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:text='@{user.firstName}' />
    </LinearLayout>
</layout>

例十二 重命名属性设置

一些属性的命名与 setter 不对应,针对这些函数,可以用 BindingMethods注解来将属性与setter绑定在一起.举个例子:android:tint属性可以这样与setImageTintList(ColorStateList) ) 绑定，而不是 setTint :

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