我解决了问题。 这是布局:

 <android.support.design.widget.TextInputLayout
           android:id="@+id/til_username"
           android:layout_width="match_parent"
           android:layout_height="wrap_content"
           android:hint="@string/username"
           >

           <android.support.v7.widget.AppCompatEditText android:id="@+id/et_username"
               android:layout_width="match_parent"
               android:layout_height="wrap_content"
               android:singleLine="true"
               />
       </android.support.design.widget.TextInputLayout>

这就是风格:

<style name="AppBaseTheme" parent="Theme.AppCompat.Light.DarkActionBar">
        <!--
            Theme customizations available in newer API levels can go in
            res/values-vXX/styles.xml, while customizations related to
            backward-compatibility can go here.
        -->
    </style>
<!-- Application theme. -->


 <style name="AppTheme" parent="AppBaseTheme">
        <!-- All customizations that are NOT specific to a particular API-level can go here. -->
        <item name="colorAccent">@color/pink</item>
        <item name="colorControlNormal">@color/purple</item>
        <item name="colorControlActivated">@color/yellow</item>
    </style>

你应该在应用程序中使用你的主题:

<application
        android:allowBackup="true"
        android:icon="@drawable/ic_launcher"
        android:label="@string/app_name"
        android:theme="@style/AppTheme" >
</application>

我建议你为TextInputLayout做风格主题，只改变强调色。设置父主题为你的应用程序基础主题:

 <style name="MyTextInputLayout" parent="MyAppThemeBase">
     <item name="colorAccent">@color/colorPrimary</item>
 </style>

 <android.support.design.widget.TextInputLayout
  android:layout_width="fill_parent"
  android:layout_height="wrap_content"
  android:theme="@style/MyTextInputLayout">

因为你必须在主应用主题中添加colorControlNormal, colorControlActivated, colorControlHighLight三项:

<!-- Base application theme. -->
    <style name="AppTheme" parent="Theme.AppCompat.Light.NoActionBar">

        <item name="colorPrimary">@color/colorPrimary</item>
        <item name="colorPrimaryDark">@color/colorPrimaryDark</item>
        <item name="colorAccent">@color/colorAccent</item>

        <item name="colorControlActivated">@color/yellow_bright</item>
        <item name="colorControlNormal">@color/yellow_black</item>

    </style>

  <style name="AppTheme2" parent="AppTheme">
    <!-- Customize your theme here. -->
    <item name="colorControlNormal">#fff</item>
    <item name="colorControlActivated">#fff</item></style>    

将此添加到styles并将TextInputLayout Theam设置为App2，它将工作;)

有太多复杂的解决方案。下面是一个改变浮动标签颜色的程序。

<com.google.android.material.textfield.TextInputLayout
   app:hintTextColor="@color/white"/>

除了更改其他属性:

更改框描边颜色:

<com.google.android.material.textfield.TextInputLayout
    app:boxStrokeColor="@color/green"

更改方框描边宽度:

<com.google.android.material.textfield.TextInputLayout 
     app:boxStrokeWidth="1.5dp"

更改编辑TextInputEditText提示颜色:

<com.google.android.material.textfield.TextInputEditText
     android:textColorHint="@color/white"

更改TextInputEditText的颜色:

<com.google.android.material.textfield.TextInputEditText           
            android:textColor="@color/white" />

如果你使用com.google.android.material.textfield，可以使用app:hintTextColor。TextInputLayout，试试这个

 <com.google.android.material.textfield.TextInputLayout
     android:layout_width="match_parent"
     android:layout_height="wrap_content"
     android:hint="@string/app_name" 
     app:hintTextColor="@android:color/white">                   

     <com.google.android.material.textfield.TextInputEditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        />
 </com.google.android.material.textfield.TextInputLayout>