获取了高度之后，我们就可以正确地设置位置了。但是，如果保证上面的布局随着我们的内容的移动，而改变现实状态呢？
经过我手动直观测试，知乎的这个界面是根据一个固定的值，来改变显示状态的，因此，我们可以监听ScrollView的滑动距离，来判断。但是ScrollView并没有给我们这样一个监听器，咋办？重写！
/**
* Created by zhaokaiqiang on 15/2/26.
*/
public class MyScrollView extends ScrollView {
private BottomListener bottomListener;
private onScrollListener scrollListener;
public MyScrollView(Context context) {
this(context, null);
}
public MyScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
if (getScrollY() + getHeight() >= computeVerticalScrollRange()) {
if (null != bottomListener) {
bottomListener.onBottom();
}
}
if (null != scrollListener) {
scrollListener.onScrollChanged(l, t, oldl, oldt);
}
}
public void setBottomListener(BottomListener bottomListener) {
this.bottomListener = bottomListener;
}
public void setScrollListener(onScrollListener scrollListener) {
this.scrollListener = scrollListener;
}
public interface onScrollListener {
public void onScrollChanged(int l, int t, int oldl, int oldt);
}
public interface BottomListener {
public void onBottom();
}
}
我们只需要重写onScrollChange()方法即可，在里面不光可以时时的得到位置的变化，还添加了一个BottomListener接口来监听滑动到底部的事件，写好之后就很简单了
mScroller.setBottomListener(this); mScroller.setScrollListener(this);
/**
* 显示上部的布局
*/
private void showTop() {
ObjectAnimator anim1 = ObjectAnimator.ofFloat(img_bar, "y", img_bar.getY(),
0);
anim1.setDuration(TIME_ANIMATION);
anim1.start();
ObjectAnimator anim2 = ObjectAnimator.ofFloat(tv_title, "y", tv_title.getY(),
img_bar.getHeight());
anim2.setInterpolator(new DecelerateInterpolator());
anim2.setDuration(TIME_ANIMATION + 200);
anim2.start();
ObjectAnimator anim4 = ObjectAnimator.ofFloat(fl_top, "y", fl_top.getY(),
0);
anim4.setDuration(TIME_ANIMATION);
anim4.start();
isTopHide = false;
}
/**
* 隐藏上部的布局
*/
private void hideTop() {
ObjectAnimator anim1 = ObjectAnimator.ofFloat(img_bar, "y", 0,
-img_bar.getHeight());
anim1.setDuration(TIME_ANIMATION);
anim1.start();
ObjectAnimator anim2 = ObjectAnimator.ofFloat(tv_title, "y", tv_title.getY(),
-tv_title.getHeight());
anim2.setDuration(TIME_ANIMATION);
anim2.start();
ObjectAnimator anim4 = ObjectAnimator.ofFloat(fl_top, "y", 0,
-(img_bar.getHeight() + tv_title.getHeight()));
anim4.setDuration(TIME_ANIMATION);
anim4.start();
isTopHide = true;
}
@Override
public void onBottom() {
if (isToolsHide) {
showTools();
}
}
@Override
public void onScrollChanged(int l, int t, int oldl, int oldt) {
if (t <= dp2px(TOP_DISTANCE_Y) && isTopHide && isAnimationFinish) {
showTop();
Log.d(TAG, "显示");
} else if (t > dp2px(TOP_DISTANCE_Y) && !isTopHide && isAnimationFinish) {
hideTop();
Log.d(TAG, "隐藏");
}
}
