ViewPager 的 Android 事件侦听器数据绑定 [英] Android Event Listener Data Binding for ViewPager

问题描述

是否可以使用 Android 绑定功能将 setOnPageChangeListener 的处理程序绑定到 XML 文件中的 ViewPager?

Is it possible to bind a handler for setOnPageChangeListener to a ViewPager in XML file with the Android Binding functionality?

演示展示了 onClick 事件，但我很好奇我可以用它实现多少事件功能.任何有关数据绑定功能的链接也会很棒.谢谢.

The demos show onClick events but I am curious as to how much event functionality I can implement with it. Any links on the capabilities of Data Binding would be great as well. Thanks.

假设示例:

example_activity.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.Handlers"/>
</data>

<android.support.v4.view.ViewPager
    android:id="@+id/pager"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"

    android:onPageChangeListener="@{handlers.pageChanged}" />
</layout>

Handler.java

package com.example.viewmodels;

import android.view.View;

public class Handlers {
    public void pageChanged(View view){}
}

编译错误是:

错误:(62) 在包 'android' 中找不到属性 'onPageChangeListener' 的资源标识符

Error:(62) No resource identifier found for attribute 'onPageChangeListener' in package 'android'

推荐答案

这是可以做到的.您需要实现自定义绑定适配器，因为 Android 支持库中没有为 View 类预定义的 BindingAdapter 类.

It is possible to do this. You need to implement a custom binding adapter because there is no BindingAdapter classes predefined for View classes from Android support libraries.

关于如何实现自定义适配器，您可以阅读 this.

For how to implement the custom adapter you may read this.

代码应该如下所示，我还没有彻底测试过:

The code should be something like the below, I haven't tested them thoroughly:

<android.support.v4.view.ViewPager
    android:id="@+id/pager"
    xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    app:onPageChangeListener="@{handlers}" />

您的 BindingAapter 代码:

Your BindingAapter code:

@BindingAdapter("onPageChangeListener")
public static void setOnPageChangeListener(ViewPager viewPager, ViewPager.OnPageChangeListener listener) {
    Log.i("setOnPageChangeListener");

    // clear listeners first avoid adding duplicate listener upon calling notify update related code
    viewPager.clearOnPageChangeListeners();
    viewPager.addOnPageChangeListener(listener);
}

附:您传递的处理程序类应该实现 ViewPager.OnPageChangeListener.

P.S. Your handler class being passed should implement ViewPager.OnPageChangeListener.

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