修复CollapsingToolbarLayout，当FitsS

分为：
 android.support.design.widget.CollapsingToolbarLayout;  // 需反射 mLastInsets
 com.google.android.material.appbar.CollapsingToolbarLayout;  // 需反射 lastInsets

public class FixCollapsingToolbarLayout extends CollapsingToolbarLayout {

    public FixCollapsingToolbarLayout(Context context) {
        super(context);
    }

    public FixCollapsingToolbarLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public FixCollapsingToolbarLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        try {
            // android.support.design.widget.CollapsingToolbarLayout;  // 需反射 mLastInsets
            // com.google.android.material.appbar.CollapsingToolbarLayout;  // 需反射 lastInsets
            Field fs = CollapsingToolbarLayout.class..getDeclaredField("mLastInsets");
            、、Field fs = this.getClass().getSuperclass().getDeclaredField("mLastInsets");
            fs.setAccessible(true);
            WindowInsetsCompat mLastInsets = (WindowInsetsCompat) fs.get(this);
            final int mode = MeasureSpec.getMode(heightMeasureSpec);
            int topInset = mLastInsets != null ? mLastInsets.getSystemWindowInsetTop() : 0;
            if (mode == MeasureSpec.UNSPECIFIED && topInset > 0) {
                // fix the bottom empty padding
                heightMeasureSpec = MeasureSpec.makeMeasureSpec(
                        getMeasuredHeight() - topInset, MeasureSpec.EXACTLY);
                super.onMeasure(widthMeasureSpec, heightMeasureSpec);
            }
        } catch (Exception e) {
            LogUtils.e(e);
        }
    }
}

或继承  android.support.design.widget.CollapsingToolbarLayout 时，使用如下：

public class FixCollapsingToolbarLayout extends CollapsingToolbarLayout {
    private boolean mLayoutReady;
    public FixCollapsingToolbarLayout(Context context) {
        super(context);
    }

    public FixCollapsingToolbarLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    public FixCollapsingToolbarLayout(Context context, AttributeSet attrs, int defStyle) {
        super(context, attrs, defStyle);
    }

    @Override
    protected void onLayout(boolean changed, int left, int top, int right, int bottom) {
        if (!mLayoutReady) {
            if (Build.VERSION.SDK_INT > Build.VERSION_CODES.KITKAT_WATCH) {
                if ((getWindowSystemUiVisibility() &
                        (SYSTEM_UI_FLAG_LAYOUT_STABLE|SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN)) ==
                        (SYSTEM_UI_FLAG_LAYOUT_STABLE|SYSTEM_UI_FLAG_LAYOUT_FULLSCREEN)) {
                    try {
                        Field mLastInsets = CollapsingToolbarLayout.class.getDeclaredField("mLastInsets");
                        mLastInsets.setAccessible(true);
                        mLastInsets.set(this, null);
                    } catch (NoSuchFieldException e) {
                        e.printStackTrace();
                    } catch (IllegalAccessException e) {
                        e.printStackTrace();
                    }
                }
            }
            mLayoutReady = true;
        }
        super.onLayout(changed, left, top, right, bottom);
    }
}