BufferTextInputLayout.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 workaround it...
        final Drawable newBg = bg.getConstantState().newDrawable();
        if (bg instanceof DrawableContainer) {
            // If we have a Drawable container, we can try and set it's 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;
        }
    }
}