页面整个布局大体上是ScrollView里面包含了一个ImageView和RecyclerView,所以先得到ImageView的高度,当ScrollView向上滑动时,设置标题栏的背景色、文字颜色,当超过ImageView的高度时,设置其背景为白色,字体为黑色。
ObservableScrollView
import android.content.Context;
import android.util.AttributeSet;
import android.view.MotionEvent;
import android.widget.ScrollView;
public class ObservableScrollView extends ScrollView {
private OnScrollChangedListener mOnScrollChangedListener;
public ObservableScrollView(Context context) {
super(context);
}
public ObservableScrollView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
}
public ObservableScrollView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public void setOnScrollChangedListener(OnScrollChangedListener onScrollChangedListener) {
this.mOnScrollChangedListener = onScrollChangedListener;
}
@Override
protected void onScrollChanged(int x, int y, int oldx, int oldy) {
super.onScrollChanged(x, y, oldx, oldy);
if (mOnScrollChangedListener != null) {
mOnScrollChangedListener.onScrollChanged(this, x, y, oldx, oldy);
}
}
@Override
public boolean onInterceptTouchEvent(MotionEvent ev) {
return false; // 此处为了演示,阻止ScrollView拦截Touch事件
}
interface OnScrollChangedListener {
void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy);
}
}
int mAlpha = 0;
scrollview.setOnScrollChangedListener(new ObservableScrollView.OnScrollChangedListener() {
@Override
public void onScrollChanged(ObservableScrollView scrollView, int x, int y, int oldx, int oldy) {
int minHeight = 50;
int maxHeight = rl_userhome_top.getMeasuredHeight();
if (maxHeight == 0) {
maxHeight = 500;
}
if (scrollView.getScrollY() <= minHeight) {
mAlpha = 0;
} else if (scrollView.getScrollY() > maxHeight) {
mAlpha = 255;
} else {
mAlpha = (scrollView.getScrollY() - minHeight) * 255 / (maxHeight - minHeight);
}
if (mAlpha <= 0) {
tv_title.setTextColor(Color.rgb(255, 255, 255));
iconColorFilter(Color.parseColor("#ffffff"));
rl_userhome_title.setBackgroundColor(Color.argb(0, 255, 255, 255));
} else if (mAlpha >= 255) {
tv_title.setTextColor(Color.rgb(0, 0, 0));
iconColorFilter(Color.parseColor("#000000"));
rl_userhome_title.setBackgroundColor(Color.argb(mAlpha, 255, 255, 255));
} else {
tv_title.setTextColor(Color.rgb(255 - mAlpha, 255 - mAlpha, 255 - mAlpha));
iconColorFilter(Color.rgb(255 - mAlpha, 255 - mAlpha, 255 - mAlpha));
rl_userhome_title.setBackgroundColor(Color.argb(mAlpha, mAlpha, mAlpha, mAlpha));
}
}
});
/**
* 标题栏/导航栏icon 颜色改变
*
* @param color
*/
private void iconColorFilter(int color) {
PorterDuffColorFilter colorFilter = new PorterDuffColorFilter(color, PorterDuff.Mode.SRC_ATOP);
iv_back.setColorFilter(colorFilter);
}