TextInputLayout.java 文件源码

private void ensureBackgroundDrawableStateWorkaround() {
  final int sdk = Build.VERSION.SDK_INT;
  if (sdk != 21 && sdk != 22) {
    // The workaround is only required on API 21-22
    return;
  }
  final Drawable bg = editText.getBackground();
  if (bg == null) {
    return;
  }

  if (!hasReconstructedEditTextBackground) {
    // This is gross. There is an issue in the platform which affects container Drawables
    // where the first drawable retrieved from resources will propagate any changes
    // (like color filter) to all instances from the cache. We'll try to work around it...

    final Drawable newBg = bg.getConstantState().newDrawable();

    if (bg instanceof DrawableContainer) {
      // If we have a Drawable container, we can try and set its constant state via
      // reflection from the new Drawable
      hasReconstructedEditTextBackground =
          DrawableUtils.setContainerConstantState(
              (DrawableContainer) bg, newBg.getConstantState());
    }

    if (!hasReconstructedEditTextBackground) {
      // If we reach here then we just need to set a brand new instance of the Drawable
      // as the background. This has the unfortunate side-effect of wiping out any
      // user set padding, but I'd hope that use of custom padding on an EditText
      // is limited.
      ViewCompat.setBackground(editText, newBg);
      hasReconstructedEditTextBackground = true;
      // Re-apply box background mode to set the EditText's box padding if in box mode.
      onApplyBoxBackgroundMode();
    }
  }
}