要实现用SeekBar控制ScrollView滚动的位置,并且ScrollView滚动时也更新SeekBar的角度,需要继承ScrollView,实现一个新的类。可以使这个类实现 SeekBar.OnSeekBarChangeListener接口。
覆盖ScrollView的onScrollChanged方法并修改SeekBar.OnSeekBarChangeListener接口中的onProgressChanged方法。关键代码如下
int heightMeasure;
@Override
protected void onSizeChanged(int w, int h, int oldw, int oldh) {
super.onSizeChanged(w, h, oldw, oldh);
heightMeasure = getMeasuredHeight();
}
@Override
protected void onScrollChanged(int l, int t, int oldl, int oldt) {
super.onScrollChanged(l, t, oldl, oldt);
// When the user scrolls, we hide navigation elements.
if (heightMeasure == 0) {
Toast.makeText(getContext(), "heightMeansu = 0", Toast.LENGTH_SHORT).show();
} else {
//获取ScrollView的第一个子View的高度,也就是ScorllView要展示的内容的高度
View firstChildView = getChildAt(0);
int firstChildViewHeight = firstChildView.getHeight();
if(firstChildViewHeight==0){
Toast.makeText(getContext(), "firstChildViewHeight = 0", Toast.LENGTH_SHORT).show();
}else{
//计算出ScrollView所处位置占整体的百分比并设置为SeekBar mSeekView的值
int progress = (int) (t * 100.0f / (firstChildViewHeight- heightMeasure));
mSeekView.setOnSeekBarChangeListener(null);
mSeekView.setProgress(progress);
mSeekView.setOnSeekBarChangeListener(this);
}
// setNavVisibility(false);
}
}
/**
* SeakBar值改变时修改ScrollView位置
* @param seekBar
* @param progress
* @param fromUser
*/
@Override
public void onProgressChanged(SeekBar seekBar, int progress, boolean fromUser) {
if (heightMeasure == 0) {
Toast.makeText(getContext(), "heightMeansu = 0", Toast.LENGTH_SHORT).show();
} else {
View firstChildView = getChildAt(0);
int firstChildViewHeight = firstChildView.getHeight();
int y = (int) ((firstChildViewHeight - heightMeasure) * progress / 100.0f);
scrollTo(0, y);
}
}