原创刨根问底掌握布局样式主题追踪edittext背景默认样式修改下划线分析距离左边有一点距离的原因

简书链接:原创刨根问底掌握布局样式主题追踪edittext背景默认样式修改下划线分析距离左边有一点距离的原因
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首先从EditText源码中发现R.attr.editTextStyle
首先要说明的是style分别是materialdesign库和来系统架构目录两种，都可以定位。

public EditText(Context context, AttributeSet attrs) {
    this(context, attrs, com.android.internal.R.attr.editTextStyle);
}

然后定位values文件夹

分析editTextStyle
得到如下

1	<item name="editTextStyle">@style/Widget.Material.EditText</item>

然后

<style name="Widget.EditText">
    <item name="focusable">true</item>
    <item name="focusableInTouchMode">true</item>
    <item name="clickable">true</item>
    <item name="background">?attr/editTextBackground</item>
    <item name="textAppearance">?attr/textAppearanceMediumInverse</item>
    <item name="textColor">?attr/editTextColor</item>
    <item name="gravity">center_vertical</item>
    <item name="breakStrategy">simple</item>
    <item name="hyphenationFrequency">@dimen/config_preferredHyphenationFrequency</item>
    <item name="defaultFocusHighlightEnabled">false</item>
</style>

定位到editTextBackground
经过源码分析，发现

1	<item name="editTextBackground">@drawable/abc_edit_text_material</item>

<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_window_focused="false" android:state_enabled="true" android:drawable="@drawable/textfield_default" />
    <item android:state_window_focused="false" android:state_enabled="false" android:drawable="@drawable/textfield_disabled" />
    <item android:state_enabled="true" android:state_focused="true" android:drawable="@drawable/textfield_selected" />
    <item android:state_enabled="true" android:drawable="@drawable/textfield_default" />
    <item android:state_focused="true" android:drawable="@drawable/textfield_disabled_selected" />
    <item android:drawable="@drawable/textfield_disabled" />
</selector>

定位appcompat 样式大致是一样的

最后得到的是这个

<inset xmlns:android="http://schemas.android.com/apk/res/android"
       android:insetLeft="@dimen/abc_edit_text_inset_horizontal_material"
       android:insetRight="@dimen/abc_edit_text_inset_horizontal_material"
       android:insetTop="@dimen/abc_edit_text_inset_top_material"
       android:insetBottom="@dimen/abc_edit_text_inset_bottom_material">

    <selector>
        <item android:state_enabled="false" android:drawable="@drawable/abc_textfield_default_mtrl_alpha"/>
        <item android:state_pressed="false" android:state_focused="false" android:drawable="@drawable/abc_textfield_default_mtrl_alpha"/>
        <item android:drawable="@drawable/abc_textfield_activated_mtrl_alpha"/>
    </selector>

</inset>