Android – Why changing Color of Default Button makes it look RECTANGLE in Android

I discovered that this can all be done in one file fairly easily. Put something like the following code in a file named custom_button.xml and then set background="@drawable/custom_button" in your button view:

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

    <item android:state_pressed="true" >
        <shape>
            <gradient
                android:startColor="@color/yellow1"
                android:endColor="@color/yellow2"
                android:angle="270" />
            <stroke
                android:width="3dp"
                android:color="@color/grey05" />
            <corners
                android:radius="3dp" />
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>

    <item android:state_focused="true" >
        <shape>
            <gradient
                android:endColor="@color/orange4"
                android:startColor="@color/orange5"
                android:angle="270" />
            <stroke
                android:width="3dp"
                android:color="@color/grey05" />
            <corners
                android:radius="3dp" />
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>

    <item>        
        <shape>
            <gradient
                android:endColor="@color/blue2"
                android:startColor="@color/blue25"
                android:angle="270" />
            <stroke
                android:width="3dp"
                android:color="@color/grey05" />
            <corners
                android:radius="3dp" />
            <padding
                android:left="10dp"
                android:top="10dp"
                android:right="10dp"
                android:bottom="10dp" />
        </shape>
    </item>
</selector>

One approach is to create an XML file like this in drawable, called whatever.xml:

<?xml version="1.0" encoding="utf-8"?> 
  <selector xmlns:android="http://schemas.android.com/apk/res/android">
    <item
        android:state_focused="true"
        android:state_pressed="true"
        android:drawable="@drawable/bgalt" />

    <item
        android:state_focused="false"
        android:state_pressed="true"
        android:drawable="@drawable/bgalt" />

    <item android:drawable="@drawable/bgnorm" />
</selector>

bgalt and bgnormare PNG images in drawable.

If you create the buttons programatically in your activity, you can set the background with:

final Button b = new Button (MyClass.this);
b.setBackgroundDrawable(getResources().getDrawable(R.drawable.whatever));

If you set your buttons' style with an XML, you would do something like:

<Button
  android:id="@+id/mybutton"
  android:background="@drawable/watever" />

And finally a link to a tutorial. Hope this helps.