Does changing the background also change the padding of a LinearLayout?

问题

I have the following LinearLayout. What I don't understand is if I set the background to another image, the padding information are reset. Is there a way to prevent this?

<LinearLayout android:id="@+id/aPanel"
    android:orientation="horizontal" android:layout_width="fill_parent"
    android:layout_height="wrap_content" android:background="@drawable/bkground"
    android:paddingLeft="15dp" android:paddingRight="15dp"> 

     <!-- some children here -->
     </LinearLayout>

I see the position of the children get shifted when I change the background drawable of the LinearLayout aPanel.

回答1:

This is the default behavior when changing the background Drawable on a View. According to Romain Guy, one of the Android developers, "The reason why setting an image resets the padding is because 9-patch images can encode padding." See his full answer in a similar question.

The fix is to reset the padding in code each time you change the background drawable.

回答2:

This is a similar question.

in short, the answer would be :

public static void setViewBackgroundWithoutResettingPadding(final View v, final int backgroundResId) {
    final int paddingBottom = v.getPaddingBottom(), paddingLeft = v.getPaddingLeft();
    final int paddingRight = v.getPaddingRight(), paddingTop = v.getPaddingTop();
    v.setBackgroundResource(backgroundResId);
    v.setPadding(paddingLeft, paddingTop, paddingRight, paddingBottom);
}

The reason for the padding being reset is because the drawable might be a 9-patch drawable .

回答3:

You can use shape to set the background with single colour or image and apply padding like this:

<shape xmlns:android="http://schemas.android.com/apk/res/android">
    <solid android:color="#FFFFFF"/>
    <corners
        android:bottomLeftRadius="8dip"
        android:topLeftRadius="8dip"/>
    <padding
        android:bottom="0dip"
        android:left="0dip"
        android:right="0dip"
        android:top="0dip"/>
</shape>

来源：https://stackoverflow.com/questions/2886140/does-changing-the-background-also-change-the-padding-of-a-linearlayout