android attrs文件注意事项

1.attrs文件注意事项:
 (1)每个 attr (属性)名称在应用程序范围内必须唯一,既无论定义几个资源文件,无论定义几个styleable,声明必须唯一
 (2)如果一个 attr 后面仅仅有一个 name ,那么这就是引用;如果不光有 name 还有 format那就是声明。test1的title 是属性的声明,其不能在其他 styleable 中再次声明;test的title则是属性的引用,其声明是在test1 中。

<?xml version="1.0" encoding="utf-8"?>
<resources>
    <declare-styleable name="test1">
        <attr name="key" format="string"/>
        <attr name="title" format="string" /><!--参考下面的title注释-->
        <attr name="summary" format="string" />
        <attr name="layout" />
        <attr name="widgetLayout" format="reference" />
        <attr name="titleMarginEnd" format="dimension"/>
        <attr name="titleWidth" format="dimension"/>
        <attr name="defValue" format="string|boolean|integer"/>
        <attr name="persistent" format="boolean"/>
        <attr name="tipText" format="string"/>
    </declare-styleable>
    <declare-styleable name="test">
        <attr name="title" /><!--只要指定format，不管和上面的format类型相同还是不同，编译时就会上面的title冲突，不指定format，编译时不会报错-->
        <attr name="layout_width" format="reference" />
        <attr name="values" format="reference" />
        <attr name="spinnerWidth" format="dimension"/>
        <attr name="spinnerHeight" format="dimension"/>
        <attr name="spinnerMode" format="string"/>
        <attr name="id" format="reference" />
    </declare-styleable>
<!-- 注意：1.attrs文件不能指定名字相同的attr（除非一个指定format,另一个不指定，参考上图的title） -->
</resources>

2.layout文件

<?xml version="1.0" encoding="utf-8"?>
<androidx.constraintlayout.widget.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:gs="http://schemas.android.com/apk/res-auto"
    xmlns:stackdump="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity">

    <!--gs和stackdump是随意指定的名字-->
    <com.stackdump.attrs.widget.CmccSpinnerPreference
        android:id="@+id/size_pref"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        app:layout_constraintBottom_toTopOf="parent"
        app:layout_constraintEnd_toStartOf="parent"
        app:layout_constraintStart_toStartOf="parent"
        app:layout_constraintTop_toTopOf="parent"
        gs:spinnerMode="hello_test"
        stackdump:title="hello" />

</androidx.constraintlayout.widget.ConstraintLayout>

3.自定义控件CmccSpinnerPreference.ajva

package com.stackdump.attrs.widget;

import android.content.Context;
import android.content.res.TypedArray;
import android.util.AttributeSet;
import android.util.Log;
import android.view.View;
import android.widget.LinearLayout;
import android.widget.Spinner;

import com.stackdump.attrs.R;

import androidx.annotation.Nullable;

/**
 * Author:stackdump
 * Date:20-2-10
 */
public class CmccSpinnerPreference extends LinearLayout {
    private static final String TAG = "CmccSpinnerPreference";

    private CharSequence[] mEntries;
    private CharSequence[] mEntryValues;
    private String mValue;
    private String mSummary;
    private String mTitle;
    private int mSelectedEntryIndex;
    private boolean mValueSet;
    private float spinnerWidth;
    private float spinnerHeight;
    private boolean dialogMode;

    private Spinner mSpinner;
    private View.OnFocusChangeListener mOnFocusChangeListener;

    public CmccSpinnerPreference(Context context) {
        this(context, null);
    }


    public CmccSpinnerPreference(Context context, @Nullable AttributeSet attrs) {
        this(context, attrs, 0);
    }

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

        TypedArray a = context.obtainStyledAttributes(attrs,
                R.styleable.test, defStyleAttr, 0);//此处为了证明test名称可随意命名，特意没有与自定义控件的名称保持相同
        mTitle = a.getString(R.styleable.test_spinnerMode);
        a.recycle();

        TypedArray a1 = context.obtainStyledAttributes(attrs,
                R.styleable.test1, defStyleAttr, 0);
        mSummary = a1.getString(R.styleable.test1_title);
        a1.recycle();
        Log.d("info","stackdump mTitle:"+mTitle+" mSummary:"+mSummary);
    }
}

4.log打印: stackdump mTitle:hello_test mSummary:hello