How to add a gradient to buttons in android through xml?

Create a new xml file and put it in drawable and then add it to button as background

gradient.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
android:shape="rectangle">
    <!--  Gradient Bg for listrow -->
   <gradient
      android:startColor="#f1f1f2"
      android:centerColor="#e7e7e8"
      android:endColor="#cfcfcf"
      android:angle="270" />
</shape>

layout.xml

 <Button
    android:id="@+id/Button01"
    android:layout_width="wrap_content"
    android:layout_height="fill_parent"
    android:layout_weight="1"
    android:background="@drawable/gradient"
    android:text="Übernehmen" >

Create gradient.xml

<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle" >

    <gradient
      android:angle="270"
      android:endColor="@color/greenstart"
      android:startColor="@color/greenend" />

</shape>

Try this :

<?xml version="1.0" encoding="utf-8"?>
<selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item android:state_pressed="true" >
        <shape>
            <solid
                android:color="#70c656" />
            <stroke
                android:width="1dp"
                android:color="#53933f" />
            <corners
                android:radius="3dp" />
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>
    <item>
        <shape>
            <gradient
                android:startColor="#70c656"
                android:endColor="#53933f"
                android:angle="270" />
            <stroke
                android:width="1dp"
                android:color="#53933f" />
            <corners
                android:radius="4dp" />
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>
</selector>

So here we go with the gradient. As above @Dusean Singh said. If you will use an angle 270 then your gradient will start from top to down : TOP -> Center -> bottom

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <gradient
        android:startColor="#FF0000"
        android:centerColor="#00FF00"
        android:endColor="#0000FF"
        android:angle="270" />
</shape>

If you will use an angle 360 then your gradient will start from left to right : Left -> Center -> Right

<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="rectangle">
    <!--  Gradient Bg for listrow -->
    <gradient
        android:startColor="#FF0000"
        android:centerColor="#00FF00"
        android:endColor="#0000FF"
        android:angle="360" />
</shape>

Here we go with the effect. and how to apply the same on button

<LinearLayout
    android:id="@+id/design_bottom_sheet"
    android:layout_alignParentBottom="true"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:orientation="horizontal"
    android:weightSum="2">
    <Button
        android:drawableLeft="@drawable/ic_grid"
        android:layout_width="match_parent"
        android:text="Find"
        android:background="@drawable/gradient_button"
        android:textColor="@color/white"
        android:textAllCaps="false"
        android:layout_height="wrap_content"
        android:layout_weight="1" />
    <Button
        android:drawableLeft="@drawable/ic_card"
        android:layout_width="match_parent"
        android:textColor="@color/white"
        android:text="Match"
        android:background="@drawable/gradient_button"
        android:textAllCaps="false"
        android:layout_height="wrap_content"
        android:layout_weight="1" />
</LinearLayout>