Jetpack之DataBinding的使用

DataBinding

数据绑定库是一种支持库，借助该库，您可以使用声明性格式（而非程序化地）将布局中的界面组件绑定到应用中的数据源。

案例一

Activity

// 步骤一：在 build.gradle 中添加 dataBinding { enabled = true }
// 步骤二：创建实体类，并在布局文件中引用它
public class OneDataActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        // 步骤三：使用 DataBindingUtil 加载布局，初始化实体类，并将实体类的值传到布局中
        ActivityDoneBinding viewDataBinding = DataBindingUtil.setContentView(this, R.layout.activity_done);
        Idol idol = new Idol("jetpack", 5);
        viewDataBinding.setIdol(idol);
        viewDataBinding.setEventHandler(new EventHandleListener(this));
    }

}

实体类

public class Idol {

    private String name;
    private int star;

    public Idol(String name, int star) {
        this.name = name;
        this.star = star;
    }

    public String getName() {
        return name;
    }

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

    public int getStar() {
        return star;
    }

    public void setStar(int star) {
        this.star = star;
    }

}

EventHandleListener

public class EventHandleListener {

    private Context context;

    public EventHandleListener(Context context) {
        this.context = context;
    }

    public void onClick(View view) {
        Toast.makeText(context, "喜欢", Toast.LENGTH_SHORT).show();
    }

}

Util

public class StarUtil {

    public static String convert(int number) {
        if (number < 1) {
            return "一星";
        } else if (number == 2) {
            return "二星";
        } else if (number == 3) {
            return "三星";
        } else if (number == 4) {
            return "四星";
        } else {
            return "五星";
        }
    }

}

布局文件

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

    <data>
        <variable
            name="idol"
            type="com.zc.mydemo.jetpack.databind.Idol" />

        <variable
            name="eventHandler"
            type="com.zc.mydemo.jetpack.databind.demo1.EventHandleListener" />

        <import type="com.zc.mydemo.jetpack.databind.StarUtil" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_horizontal"
        android:orientation="vertical"
        tools:context=".jetpack.databind.demo1.OneDataActivity">

        <ImageView
            android:id="@+id/image"
            android:layout_width="300dp"
            android:layout_height="300dp"
            android:layout_marginTop="20dp" />

        <TextView
            android:id="@+id/name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="@{idol.name}"
            android:textSize="20sp" />

        <TextView
            android:id="@+id/star"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="@{StarUtil.convert(idol.star)}"
            android:textSize="20sp" />

        <Button
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:onClick="@{eventHandler.onClick}"
            android:text="点赞" />

    </LinearLayout>

</layout>

案例二

Activity

public class TwoDataActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        ActivityDtwoBinding viewDataBinding = DataBindingUtil.setContentView(this, R.layout.activity_dtwo);
        Idol idol = new Idol("jetpack", 5);
        viewDataBinding.setIdol(idol);
    }

}

布局文件

<?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"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <variable
            name="idol"
            type="com.zc.mydemo.jetpack.databind.Idol" />
    </data>

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:gravity="center_horizontal"
        android:orientation="vertical"
        tools:context=".jetpack.databind.demo2.TwoDataActivity">

        <ImageView
            android:id="@+id/image"
            android:layout_width="300dp"
            android:layout_height="300dp"
            android:layout_marginTop="20dp" />

        <!-- 二级布局的传参 idols：二级布局中的 （variable -> name） 的值 -->
        <include
            layout="@layout/activity_dtwo_ll"
            app:idols="@{idol}" />

    </LinearLayout>

</layout>

二级布局：activity_dtwo_ll.xml

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

    <data>
        <variable
            name="idols"
            type="com.zc.mydemo.jetpack.databind.Idol" />

        <import type="com.zc.mydemo.jetpack.databind.StarUtil" />
    </data>

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

        <TextView
            android:id="@+id/name"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="@{idols.name}"
            android:textSize="20sp" />

        <TextView
            android:id="@+id/star"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_marginTop="20dp"
            android:text="@{StarUtil.convert(idols.star)}"
            android:textSize="20sp" />

    </LinearLayout>

</layout>

案例三

Activity

public class ThreeDataActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        
        ActivityThreeBinding binding = DataBindingUtil.setContentView(this, R.layout.activity_three);
//        binding.setLocalImage(R.drawable.ic_launcher_background);       // 加载本地图片
        binding.setNetImage("<网络图片的URL>");            // 加载网络图片
    }

}

BindingAdapter

public class ImageBindingAdapter {

    // 加载网络图片（第一个参数必须是ImageView）
    @BindingAdapter("image")
    public static void setImage(ImageView imageView, String url) {
        if (!TextUtils.isEmpty(url)) {
            Picasso.with(imageView.getContext()).load(url).into(imageView);
        } else {
            imageView.setBackgroundColor(Color.GRAY);
        }
    }

    // 加载本地图片
    @BindingAdapter("image")
    public static void setImage(ImageView imageView, int res) {
        imageView.setImageResource(res);
    }

    // 参数可选 （requireAll：false表示value值中有一个出现就会执行方法；true表示value值全部出现才会执行方法）
    @BindingAdapter(value = {"image", "defaultImageResource"}, requireAll = false)
    public static void setImage(ImageView imageView, String url, int res) {
        if (!TextUtils.isEmpty(url)) {
            Picasso.with(imageView.getContext()).load(url).into(imageView);
        } else {
            imageView.setImageResource(res);
        }
    }

}

布局文件

<?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"
    xmlns:tools="http://schemas.android.com/tools">

    <data>
        <variable
            name="netImage"
            type="String" />

        <variable
            name="localImage"
            type="int" />
    </data>

    <RelativeLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        tools:context=".jetpack.databind.demo3.ThreeDataActivity">

        <ImageView
            android:id="@+id/image"
            android:layout_width="300dp"
            android:layout_height="300dp"
            app:image="@{netImage}"
            app:defaultImageResource="@{localImage}"
            android:layout_centerInParent="true" />

    </RelativeLayout>

</layout>
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