先上listview滑动改变标题栏背景渐变效果图,透明转变成不透明效果:
图1:
图2:
图3:
图4:
我用的是小米note手机,状态栏高度是55px,后面会提到,这里先做个说明:
下面的内容包含了所有代码和一些测试数据:
代码:
代码很简单,也做了注释,这里就不废话了。
先来布局文件:
activity的布局
activity_main_10
<relativelayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical"> <listview android:id="@+id/listvew" android:layout_width="match_parent" android:layout_height="match_parent"/> <!--标题栏,这里简单写个textview--> <textview android:id="@+id/title_tv" android:layout_width="match_parent" android:layout_height="wrap_content" android:background="#00000000" android:gravity="center" android:orientation="vertical" android:padding="5dp" android:textsize="30sp"/> </relativelayout>
listview头布局
head_layout
<?xml version="1.0" encoding="utf-8"?> <linearlayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" android:orientation="vertical"> <imageview android:id="@+id/head_iv" android:layout_width="match_parent" android:layout_height="150dp" android:background="@mipmap/ch"/> </linearlayout>
listview的item布局
listview_item_layout
<?xml version="1.0" encoding="utf-8"?> <framelayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="50dp"> <textview android:id="@+id/item_tv" android:layout_width="match_parent" android:layout_height="match_parent" android:gravity="center" android:textsize="15sp"> </textview> </framelayout>
功能代码:
mainactivity10
import android.app.activity; import android.content.context; import android.os.bundle; import android.view.layoutinflater; import android.view.view; import android.view.viewgroup; import android.widget.abslistview; import android.widget.baseadapter; import android.widget.imageview; import android.widget.listview; import android.widget.textview; import java.util.arraylist; public class mainactivity10 extends activity { private textview title_tv; private listview listvew; //listview的头 private view headview; //listview头中包含的布局。这里仅仅是一个imageview private imageview head_iv; private arraylist<string> datalist; private myadapter myadapter; //listview的头部(这里是imageview)顶部距离屏幕顶部(包含状态栏)的距离 //注:这个高度,是头布局在屏幕里才会计算的,出了屏幕,就不会变了 private int height; //listview的头部的真实高度。头布局的整体高度,因为这个demo只简单写了个imageview作为头部,所以imageview的高度,就是头部的高度 private int headviewheight; private context context; @override protected void oncreate(bundle savedinstancestate) { super.oncreate(savedinstancestate); setcontentview(r.layout.activity_main_10); context = this; title_tv = (textview) findviewbyid(r.id.title_tv); listvew = (listview) findviewbyid(r.id.listvew); headview = layoutinflater.from(this).inflate(r.layout.head_layout, null); head_iv = (imageview) headview.findviewbyid(r.id.head_iv); //添加listview的头布局 listvew.addheaderview(headview); datalist = new arraylist<>(); for (int i = 0; i < 50; i++) { datalist.add("==" + i + "=="); } myadapter = new myadapter(); listvew.setadapter(myadapter); listvew.setonscrolllistener(new abslistview.onscrolllistener() { @override public void onscrollstatechanged(abslistview view, int scrollstate) { } @override public void onscroll(abslistview view, int firstvisibleitem, int visibleitemcount, int totalitemcount) { int location[] = new int[2]; /** * public void getlocationinwindow(@size(2) int[] location) * * <p>computes 计算 the coordinates 坐标 of this view in its window. the argument 参数 * must be an array of two integers. after the method returns, the array * contains 包含 the x and y location in that order.</p> * * @param location an array of two integers in which to hold the coordinates */ head_iv.getlocationinwindow(location); //listview的头部(这里是imageview)顶部距离屏幕顶部(包含状态栏)的距离 height = location[1]; headviewheight = head_iv.getheight(); utils.printlogdata("==location==0==" + location[0]); utils.printlogdata("==location==1==" + location[1]); utils.printlogdata("==height==" + height); utils.printlogdata("==headviewheight==" + headviewheight); //在head_layout.xml中,固定设置了150dp的高度,用于和上面测量的对比 utils.printlogdata("==setheigth==" + dip2px(150)); handletitlebarcolorevaluate(); } }); } // 处理标题栏颜色渐变 private void handletitlebarcolorevaluate() { //比例 float fraction; if (height > 0) { fraction = 1f - height * 1f / 60; if (fraction < 0f) { fraction = 0f; } title_tv.setalpha(fraction); return; } //高度值是负数,但是负号仅仅是表示方向,取绝对值 float space = math.abs(height) * 1f; // 标题栏的高度 fraction = space / headviewheight; if (fraction < 0f) fraction = 0f; if (fraction > 1f) fraction = 1f; title_tv.setalpha(1f); if (fraction >= 1f) { title_tv.setbackgroundcolor(0xffec434b); } else { //根据比例,生成一个按比例的颜色值 title_tv.setbackgroundcolor(chencolorutils.getnewcolorbystartendcolor(context, fraction, r.color.transparent, r.color.red)); } if (fraction >= 0.8f) { title_tv.settextcolor(chencolorutils.getnewcolorbystartendcolor(context, fraction, r.color.transparent, r.color.black)); title_tv.settext("标题栏"); } else { title_tv.settext(""); } } private class myadapter extends baseadapter { @override public int getcount() { return datalist.size(); } @override public object getitem(int position) { return null; } @override public long getitemid(int position) { return 0; } @override public view getview(int position, view convertview, viewgroup parent) { viewholder holder; if (convertview == null) { convertview = layoutinflater.from(context).inflate(r.layout.listview_item_layout, null); holder = new viewholder(); holder.item_tv = (textview) convertview.findviewbyid(r.id.item_tv); convertview.settag(holder); } else { holder = (viewholder) convertview.gettag(); } holder.item_tv.settext(datalist.get(position)); return convertview; } private class viewholder { private textview item_tv; } } /** * dip转换px */ public int dip2px(int dip) { final float scale = context.getresources().getdisplaymetrics().density; return (int) (dip * scale + 0.5f); } }
颜色:
colors.xml中添加
<color name="red">#ec434b</color> <color name="transparent">#00000000</color> <color name="black">#ff000000</color>
工具类代码:
打印日志工具:
import android.util.log; public class utils { public static void printlogdata(string data) { log.e("chen", data); } }
颜色工具:
import android.content.context; public class chencolorutils { // 成新的颜色值 public static int getnewcolorbystartendcolor(context context, float fraction, int startvalue, int endvalue) { return evaluate(fraction, context.getresources().getcolor(startvalue), context.getresources().getcolor(endvalue)); } /** * 成新的颜色值 * @param fraction 颜色取值的级别 (0.0f ~ 1.0f) * @param startvalue 开始显示的颜色 * @param endvalue 结束显示的颜色 * @return 返回生成新的颜色值 */ public static int evaluate(float fraction, int startvalue, int endvalue) { int starta = (startvalue >> 24) & 0xff; int startr = (startvalue >> 16) & 0xff; int startg = (startvalue >> 8) & 0xff; int startb = startvalue & 0xff; int enda = (endvalue >> 24) & 0xff; int endr = (endvalue >> 16) & 0xff; int endg = (endvalue >> 8) & 0xff; int endb = endvalue & 0xff; return ((starta + (int) (fraction * (enda - starta))) << 24) | ((startr + (int) (fraction * (endr - startr))) << 16) | ((startg + (int) (fraction * (endg - startg))) << 8) | ((startb + (int) (fraction * (endb - startb)))); } }
测试数据:
界面刚启动
05-18 16:19:25.386 18718-18718/com.chen e/chen: ==location==0==0
05-18 16:19:25.387 18718-18718/com.chen e/chen: ==location==1==0
05-18 16:19:25.387 18718-18718/com.chen e/chen: ==height==0
05-18 16:19:25.387 18718-18718/com.chen e/chen: ==headviewheight==0
05-18 16:19:25.387 18718-18718/com.chen e/chen: ==setheigth==413
从时间上看,启动约150毫秒(0.15秒)后
05-18 16:19:25.531 18718-18718/com.chen e/chen: ==location==0==0
05-18 16:19:25.531 18718-18718/com.chen e/chen: ==location==1==55
05-18 16:19:25.531 18718-18718/com.chen e/chen: ==height==55
05-18 16:19:25.531 18718-18718/com.chen e/chen: ==headviewheight==413
05-18 16:19:25.531 18718-18718/com.chen e/chen: ==setheigth==413
小米note,状态栏高度是55像素。所以,一开始的时候,图片距离屏幕顶部的高度就是55
向上滑动,当头布局完全出到屏幕外面后,继续滑动,打印数据不会变。
即:头布局顶部距离屏幕顶部的高度(距离)不变。因为这个高度,只会在view在屏幕中才能获取到。
详见注释
05-18 17:01:02.151 16873-16873/com.chen e/chen: ==height==-412
05-18 17:01:02.167 16873-16873/com.chen e/chen: ==height==-412
05-18 17:01:02.200 16873-16873/com.chen e/chen: ==height==-412
05-18 17:01:02.233 16873-16873/com.chen e/chen: ==height==-412
05-18 17:01:02.316 16873-16873/com.chen e/chen: ==height==-412
05-18 17:01:02.332 16873-16873/com.chen e/chen: ==height==-412
05-18 17:01:02.349 16873-16873/com.chen e/chen: ==height==-412
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