Question

我在ScrollView上扩充视图。

我需要获取事件，当滚动其中一个视图（例如，最后一个或特殊类型）变为可见时（在屏幕区域中）。

Answer 1

如果视图更改了可见性，则会调用onlayout方法，您可以尝试覆盖该方法并检查其状态。

Answer 2

您需要覆盖视图的onVisibilityChanged()。当其中一个视图的祖先改变可见性时，也会调用此方法。

Answer 3

这让我夸大了我的GridView并获得了你想要的东西

public class MyGrideView extends GridView {

    boolean expanded = false;

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

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

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

    public boolean isExpanded() {
        return expanded;
    }

    @Override
    public void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        // HACK! TAKE THAT ANDROID!
        if (isExpanded()) {
            // Calculate entire height by providing a very large height hint.
            // But do not use the highest 2 bits of this integer; those are
            // reserved for the MeasureSpec mode.
            int expandSpec = MeasureSpec.makeMeasureSpec(
                    Integer.MAX_VALUE >> 2, MeasureSpec.AT_MOST);
            super.onMeasure(widthMeasureSpec, expandSpec);

            ViewGroup.LayoutParams params = getLayoutParams();
            params.height = getMeasuredHeight();
        } else {
            super.onMeasure(widthMeasureSpec, heightMeasureSpec);
        }
    }

    public void setExpanded(boolean expanded) {
        this.expanded = expanded;
    }

}

我怎样才能看到该视图变得可见

3 个答案: