android 搞定标题随scrollview滑动变色

package com.zjtd.bzcommunity.lib;import android.content.Context;import android.util.AttributeSet;import android.widget.ScrollView;public class myScrollView extends ScrollView {    public myScrollView(Context context) {          super(context);      }        public myScrollView(Context context, AttributeSet attrs) {          super(context, attrs);      }    //    public myScrollView(Context context, AttributeSet attrs, int defStyle) {  //        super(context, attrs, defStyle);  //    }          /**     * 公共接口：ScrollView滚动监听     */    public interface OnScrollChangedListener {          void onScrollChanged(ScrollView who, int x, int y, int oldx, int oldy);      }        private OnScrollChangedListener mOnScrollChangedListener;        @Override      protected void onScrollChanged(int x, int y, int oldx, int oldy) {          super.onScrollChanged(x, y, oldx, oldy);          if (mOnScrollChangedListener != null) {          //使用公共接口触发滚动信息的onScrollChanged方法，将滚动位置信息暴露给外部            mOnScrollChangedListener.onScrollChanged(this, x, y, oldx, oldy);          }      }        /**     * 暴露给外部的方法：设置滚动监听     * @param listener     */    public void setOnScrollChangedListener(OnScrollChangedListener listener) {          mOnScrollChangedListener = listener;      }  }

布局：

android:id="@+id/mymyscrollview"
android:layout_width="fill_parent"
android:layout_height="fill_parent" >

android:layout_width="match_parent"
android:layout_height="wrap_content"
android:layout_marginBottom="60dp"
android:orientation="vertical" >

Activity:

private RelativeLayout layout_top_search; // 顶部渐变布局
private myScrollView mScrollView; // 整体ScrollView
private static final int START_ALPHA = 0;
private static final int END_ALPHA = 255;
private int fadingHeight = 600; // 当ScrollView滑动到什么位置时渐变消失（根据需要进行调整）
private Drawable drawable; // 顶部渐变布局需设置的Drawable

//-----------------------init-------------- drawable = getResources().getDrawable(R.color.red);
drawable.setAlpha(START_ALPHA);
layout_top_search.setBackgroundDrawable(drawable);
mScrollView.setOnScrollChangedListener(scrollChangedListener);

/**
* 公共接口：ScrollView的滚动监听 p l
*/
private OnScrollChangedListener scrollChangedListener = new OnScrollChangedListener() {
@Override
public void onScrollChanged(ScrollView who, int x, int y, int oldx,
int oldy) {
if (y > fadingHeight) {
y = fadingHeight; // 当滑动到指定位置之后设置颜色为纯色，之前的话要渐变---实现下面的公式即可

relativela_id.setBackgroundColor(Color.WHITE);
} else if (y < 0) {
y = 0;
} else {
relativela_id.setBackgroundColor(0x99FFFFFF);
}
drawable.setAlpha(y * (END_ALPHA - START_ALPHA) / fadingHeight
+ START_ALPHA);

}
};

布局：

Activity:

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