使用XML无法为Button添加边框，请求排查问题

Hey there! Let's dig into why your button's border isn't showing up—since the button displays and works as expected otherwise, it's almost certainly a small oversight in your styling setup. Since I can't view the screenshot content directly, here are the most common issues to check based on typical Android button border problems:

Common Fixes to Try #

• Double-check how you're applying the style in your main XML
  Make sure you're assigning the style correctly to your Button element (like style="@style/button_style4") and that you aren't overriding it with an android:background attribute set to a solid color or another drawable. If you set a direct background, it'll cover your border style entirely.

• Verify your button_style4.xml drawable structure
  For a border to appear, your drawable should use a <shape> (usually rectangle) with a <stroke> tag. Common missteps here include:

  • Forgetting to set android:width on the <stroke> (if this is 0dp, the border will be invisible)
  • Using a border color that matches the button's background or your screen's background (so it blends in completely)
  • Having a <solid> fill that covers the stroke—if you want a solid background and a border, ensure the <stroke> is defined properly (it should sit on top of the solid fill by default, but check your order and padding if needed)

  Here's a working example of a bordered button drawable for reference:

  <?xml version="1.0" encoding="utf-8"?>
  <shape xmlns:android="http://schemas.android.com/apk/res/android"
      android:shape="rectangle">
      <!-- Optional solid background color -->
      <solid android:color="@color/white" />
      <!-- Border: width and color are mandatory for visibility -->
      <stroke
          android:width="2dp"
          android:color="@color/blue" />
      <!-- Optional rounded corners -->
      <corners android:radius="8dp" />
  </shape>
  

• Rule out theme conflicts
  If you're using a Material Components theme, the default button styling might apply a tint that hides your custom border. Try adding android:backgroundTint="@null" (or app:backgroundTint="@null" if using MaterialButton) to your Button element to disable the default tint.

• Check your resource directory placement
  Ensure button_style4.xml is saved in the res/drawable folder (not a version-specific folder like drawable-v24 unless you intentionally want it only for newer APIs) so it's accessible across all your app's supported devices.

If none of these resolve the issue, sharing the actual code from both your main XML layout and button_style4.xml would help pinpoint the exact problem!

内容的提问来源于stack exchange，提问作者Tim Jansen