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>

而不是Brahmam Yamani的答案，我更喜欢使用Widget.Design.TextInputLayout作为父。这确保了所有必需的项都存在，即使不是所有项都被覆盖。在Yamanis的答案中，如果调用setErrorEnabled(true)，应用程序将崩溃与一个无法解析的资源。

简单地更改样式如下:

<style name="TextLabel" parent="Widget.Design.TextInputLayout">
    <!-- Hint color and label color in FALSE state -->
    <item name="android:textColorHint">@color/Color Name</item> 
    <item name="android:textSize">20sp</item>
    <!-- Label color in TRUE state and bar color FALSE and TRUE State -->
    <item name="colorAccent">@color/Color Name</item>
    <item name="colorControlNormal">@color/Color Name</item>
    <item name="colorControlActivated">@color/Color Name</item>
 </style>

<com.google.android.material.textfield.TextInputLayout
    android:hint="Hint"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:theme="@style/TextInputLayoutHint">

    <androidx.appcompat.widget.AppCompatEditText
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:inputType="text"
        android:maxLines="1"
        android:paddingTop="@dimen/_5sdp"
        android:paddingBottom="@dimen/_5sdp"
        android:textColor="#000000"
        android:textColorHint="#959aa6" />

</com.google.android.material.textfield.TextInputLayout>

res /价值/ styles.xml

<style name="TextInputLayoutHint" parent="">
    <item name="android:textColorHint">#545454</item>
    <item name="colorControlActivated">#2dbc99</item>
    <item name="android:textSize">11sp</item>
</style>

找到答案，使用android.support.design:hintTextAppearance属性设置自己的浮动标签外观。

例子:

<android.support.design.widget.TextInputLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    app:hintTextAppearance="@style/TextAppearance.AppCompat">

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

  <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;)

我尝试使用android:textColorHint在android.support.design.widget. textinputlayout它工作得很好。

        <android.support.design.widget.TextInputLayout
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:textColorHint="@color/colorAccent">

            <EditText
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:hint="Hello"
                android:imeActionLabel="Hello"
                android:imeOptions="actionUnspecified"
                android:maxLines="1"
                android:singleLine="true"/>

        </android.support.design.widget.TextInputLayout>