为什么忽略此自定义视图属性? [英] Why is this custom view attribute ignored?

问题描述

我正在尝试使用数据绑定库，如此Android开发人员帖子中所述.. >

为此，该帖子说，首先需要一种带有<layout>标记的布局:

<?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="wrap_content">

        <TextView android:id="@android:id/text1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:attribute='@{"name"}'/>
    </LinearLayout>
</layout>

这时，导致布局的原因ClassNotFoundException膨胀时.我发现摆脱它的唯一方法是添加<data></data>节点，即使Android Developers帖子中不存在该节点:

<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
    <data></data>
    ...
</layout>

(该帖子未提及它，但是我必须按照

但是，永远不会调用bindAttribute方法.我的构建文件夹中确实看到了布局的生成代码，但没有其他反应.

为什么我的BindingAdapter被忽略?

解决方案

我找到了解决问题的方法，但我没有正确创建绑定:

按照指南的第一步，我使用了，但对于ListView项目，您需要在Adapter的ViewHolder中使用ItemBinding.inflate:

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    ViewDataBinding binding = DataBindingUtil.inflate(
            LayoutInflater.from(parent.getContext()),
                    R.layout.item, parent, false);
    return new ViewHolder(binding.getRoot());
}

I am trying to define an attribute for any view using the Data Binding Library, as explained in this Android Developers post.

To do so, the post says one first needs a layout with an enclosing <layout> tag:

<?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="wrap_content">

        <TextView android:id="@android:id/text1"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            app:attribute='@{"name"}'/>
    </LinearLayout>
</layout>

At this point, the layout caused a ClassNotFoundException when inflated. The only way I found to get rid of it was to add a <data></data> node, even if it was absent from the Android Developers post:

<layout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto">
    <data></data>
    ...
</layout>

(The post does not mention it, but I had to enable dataBinding in my build.gradle as recommended in the Guide before I could build.)

The post then explains how to write a BindingAdapter method to process the attribute:

import android.databinding.BindingAdapter;
import android.util.Log;
import android.view.View;

public class AttributesBindingAdapter {
    @BindingAdapter("bind:attribute")
    public static void bindAttribute(View view, String attributeName){
        Log.e("PLN", attributeName);
    }
}

However, the bindAttribute method is never called. I do see the generated code for the layout in my build folder, but nothing else happens.

Why is my BindingAdapter ignored?

解决方案

I found the solution to my problem, I was not creating the Binding correctly:

Following the first steps of the Guide, I used DataBindingUtil.setContentView, but for ListView items you need to use ItemBinding.inflate in the Adapter's ViewHolder:

@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
    ViewDataBinding binding = DataBindingUtil.inflate(
            LayoutInflater.from(parent.getContext()),
                    R.layout.item, parent, false);
    return new ViewHolder(binding.getRoot());
}

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