最近项目中用到了滑动页面,也就是和目前市场上很火的"今日头条"页面滑动类似,在网上找了一下,大部分都是用viewpager来实现的,刚开始我用的是viewpager+viewgroup,上面的标题按钮用的是horizontalscrollview,写完之后感觉效果比较生硬,果断换掉,发现了一个效果比较好的第三方,也就是今天的主题:pagerslidingtabstrip.好了,下面来具体介绍一下pagerslidingtabstrip,进行一下源码解析.
一、看一下demo的样子吧
二、把pagerslidingtabstrip导入我们的项目中
然后在我们的布局文件中进行声明:
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<span style="font-size:14px;"><?xml version="1.0" encoding="utf-8"?> <linearlayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res/com.hankkin.pagerslidingtabstrip" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <com.hankkin.pagerslidingtabstrip.view.pagerslidingtabstrip android:id="@+id/tab" app:pstsshouldexpand="false" app:pstsunderlineheight="2dp" app:pstsindicatorheight="2dp" app:pstsindicatorcolor="@android:color/holo_blue_light" app:selectedtabtextcolor="@android:color/holo_blue_light" app:pstsdividercolor="@android:color/transparent" app:pststabbackground="@drawable/background" android:background="@android:color/white" android:layout_width="match_parent" android:layout_height="55dp"/> <android.support.v4.view.viewpager android:id="@+id/pager" android:layout_width="match_parent" android:layout_height="match_parent"/> </linearlayout></span><span style="font-size:18px;"> </span> |
上面的也就是我们的标题滑动按钮,下面的viewpager用来存放我们的内容
三、创建adapter
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<span style="font-size:14px;">package com.hankkin.pagerslidingtabstrip.adapter; import android.support.v4.app.fragment; import android.support.v4.app.fragmentmanager; import android.support.v4.app.fragmentpageradapter; import com.hankkin.pagerslidingtabstrip.fragment.androidfragment; import com.hankkin.pagerslidingtabstrip.fragment.javafragment; import com.hankkin.pagerslidingtabstrip.fragment.objectcfragment; import java.util.list; public class myadapter extends fragmentpageradapter { private androidfragment androidfragment; private javafragment javafragment; private objectcfragment objectcfragment; private string[] titles; public myadapter(fragmentmanager fm,string[] titles) { super(fm); this.titles = titles; } @override public fragment getitem(int position) { switch (position) { case 0: if (androidfragment == null) { androidfragment = new androidfragment(); } return androidfragment; case 1: if (javafragment == null) { javafragment = new javafragment(); } return javafragment; case 2: if (objectcfragment == null) { objectcfragment = new objectcfragment(); } return objectcfragment; default: return null; } } @override public int getcount() { return titles.length; } public string getpagetitle(int i){ return titles[i]; } } </span> |
我这里用的是碎片fragment,最下面的getpagetitle()是我们的pagerslidingtabstrip中的方法,用来获取标题
接下来我们初始化pagerslidingtabstrip和viewpager还有我们的碎片
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<span style="font-size:14px;"> private void initviews(){ fragments = new arraylist<>(); pagertab = (pagerslidingtabstrip) findviewbyid(r.id.tab); pager = (viewpager) findviewbyid(r.id.pager); for (int i=0;i<titles.length;i++){ fragment fragment = new fragment(); fragments.add(fragment); } adapter = new myadapter(getsupportfragmentmanager(),titles); pager.setadapter(adapter); pagertab.setviewpager(pager); }</span> |
在adapter中利用碎片管理器获取我们的碎片和标题相对应上.这里面需要注意提一下,如果碎片的个数比较少我们可以手动创建碎片,如果像今日头条很多的话也没关系,动态创建fragment,因为我们可以看到头条的每个碎片中的内容都是类似的,所以说动态创建也未尝不可,只有个别特殊的我们也可以特殊处理.
就这么简单就可以实现类似头条的页面滑动效果,下面我们来看一下pagerslidingtabstrip的源码吧,看懂了之后也方便我们进行改进.
四、pagerslidingtabstrip源码解析
首先我们看几个比较重要的属性
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private int indicatorcolor = 0xff666666;// 滑动指示器颜色 private int underlinecolor = 0x1a000000;//在视图的底部的全宽度的线pstsunderlinecolor颜色 private int dividercolor = 0x1a000000;//选项卡之间的分隔pstsdividercolor颜色 private boolean shouldexpand = false;//pstsshouldexpand如果设置为true，每个标签都给予同样的重量，默认为false private boolean textallcaps = true;//pststextallcaps如果为真，所有选项卡标题都是大写，默认为true private int scrolloffset = 52;//pstsscrolloffset卷轴被选择的标签的偏移 private int indicatorheight = 8;//滑动指示器pstsindicatorheight private int underlineheight = 2;//在视图的底部的全宽度的线pstsunderlineheight高度 private int dividerpadding = 12;//pstsdividerpadding顶部和底部填充的分频器 private int tabpadding = 24;//pststabpaddingleftright左、右填充每个选项卡 private int dividerwidth = 1;//选项卡分割线宽度 private int tabtextsize = 12;//选项卡字体大小 private int tabtextcolor = 0xff666666;//选项卡字体颜色 private int selectedtabtextcolor = 0xff666666;//当前选中字体颜色 private typeface tabtypeface = null; private int tabtypefacestyle = typeface.normal; private int lastscrollx = 0; private int tabbackgroundresid = r.drawable.background;//pststabbackground背景绘制的每个标签，应该是一个statelistdrawable |
我们可以自己定义这些属性的值,因为可能默认的不太好看
1.首先看一下我们的构造会初始化一些什么属性
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<span style="font-size:14px;">public pagerslidingtabstrip(context context, attributeset attrs, int defstyle) { super(context, attrs, defstyle); setfillviewport(true);//默认使子view可以拉伸来填满整个屏幕 setwillnotdraw(false);//默认不执行ondraw()方法 //初始化盛放按钮标题的线性布局 tabscontainer = new linearlayout(context); tabscontainer.setorientation(linearlayout.horizontal); tabscontainer.setlayoutparams(new layoutparams(layoutparams.match_parent, layoutparams.match_parent)); addview(tabscontainer); displaymetrics dm = getresources().getdisplaymetrics(); //导入相应资源文件 scrolloffset = (int) typedvalue.applydimension(typedvalue.complex_unit_dip, scrolloffset, dm); indicatorheight = (int) typedvalue.applydimension(typedvalue.complex_unit_dip, indicatorheight, dm); underlineheight = (int) typedvalue.applydimension(typedvalue.complex_unit_dip, underlineheight, dm); dividerpadding = (int) typedvalue.applydimension(typedvalue.complex_unit_dip, dividerpadding, dm); tabpadding = (int) typedvalue.applydimension(typedvalue.complex_unit_dip, tabpadding, dm); dividerwidth = (int) typedvalue.applydimension(typedvalue.complex_unit_dip, dividerwidth, dm); tabtextsize = (int) typedvalue.applydimension(typedvalue.complex_unit_sp, tabtextsize, dm); // get system attrs (android:textsize and android:textcolor) typedarray a = context.obtainstyledattributes(attrs, attrs); tabtextsize = a.getdimensionpixelsize(0, tabtextsize); tabtextcolor = a.getcolor(1, tabtextcolor); a.recycle(); // get custom attrs a = context.obtainstyledattributes(attrs, r.styleable.pagerslidingtabstrip); indicatorcolor = a.getcolor(r.styleable.pagerslidingtabstrip_pstsindicatorcolor, indicatorcolor); //tab文字选中时的颜色,默认和滑动指示器的颜色一致 selectedtabtextcolor=a.getcolor(r.styleable.pagerslidingtabstrip_selectedtabtextcolor, indicatorcolor); //初始化属性样式 underlinecolor = a.getcolor(r.styleable.pagerslidingtabstrip_pstsunderlinecolor, underlinecolor); dividercolor = a.getcolor(r.styleable.pagerslidingtabstrip_pstsdividercolor, dividercolor); indicatorheight = a.getdimensionpixelsize(r.styleable.pagerslidingtabstrip_pstsindicatorheight, indicatorheight); underlineheight = a.getdimensionpixelsize(r.styleable.pagerslidingtabstrip_pstsunderlineheight, underlineheight); dividerpadding = a.getdimensionpixelsize(r.styleable.pagerslidingtabstrip_pstsdividerpadding, dividerpadding); tabpadding = a.getdimensionpixelsize(r.styleable.pagerslidingtabstrip_pststabpaddingleftright, tabpadding); tabbackgroundresid = a.getresourceid(r.styleable.pagerslidingtabstrip_pststabbackground, tabbackgroundresid); shouldexpand = a.getboolean(r.styleable.pagerslidingtabstrip_pstsshouldexpand, shouldexpand); scrolloffset = a.getdimensionpixelsize(r.styleable.pagerslidingtabstrip_pstsscrolloffset, scrolloffset); textallcaps = a.getboolean(r.styleable.pagerslidingtabstrip_pststextallcaps, textallcaps); a.recycle(); rectpaint = new paint(); rectpaint.setantialias(true); rectpaint.setstyle(style.fill); dividerpaint = new paint(); dividerpaint.setantialias(true); dividerpaint.setstrokewidth(dividerwidth); defaulttablayoutparams = new linearlayout.layoutparams(layoutparams.wrap_content, layoutparams.match_parent); expandedtablayoutparams = new linearlayout.layoutparams(0, layoutparams.match_parent, 1.0f); if (locale == null) { locale = getresources().getconfiguration().locale; } }</span> |
这些基本都能看懂,主要都是初始化一些属性,代码中也有相应的注释,就不一一介绍了
2.定义viewpager滑动监听器,设置当前pager的位置
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<span style="font-size:14px;">private class pagelistener implements onpagechangelistener { @override public void onpagescrolled(int position, float positionoffset, int positionoffsetpixels) { currentposition = position; currentpositionoffset = positionoffset; scrolltochild(position, (int) (positionoffset * tabscontainer.getchildat(position).getwidth())); invalidate(); if (delegatepagelistener != null) { delegatepagelistener.onpagescrolled(position, positionoffset, positionoffsetpixels); } } @override public void onpagescrollstatechanged(int state) { if (state == viewpager.scroll_state_idle) { scrolltochild(pager.getcurrentitem(), 0); } if (delegatepagelistener != null) { delegatepagelistener.onpagescrollstatechanged(state); } } @override public void onpageselected(int position) { selectedposition = position; updatetabstyles(); if (delegatepagelistener != null) { delegatepagelistener.onpageselected(position); } } }</span> |
3.更新标题样式,也就是滑动到当前标题下设置标题状态
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<span style="font-size:14px;">private void updatetabstyles() { for (int i = 0; i < tabcount; i++) { view v = tabscontainer.getchildat(i); v.setbackgroundresource(tabbackgroundresid); if (v instanceof textview) { textview tab = (textview) v; tab.settextsize(typedvalue.complex_unit_px, tabtextsize); tab.settypeface(tabtypeface, tabtypefacestyle); tab.settextcolor(tabtextcolor); // setallcaps() is only available from api 14, so the upper case is made manually if we are on a // pre-ics-build if (textallcaps) { if (build.version.sdk_int >= build.version_codes.ice_cream_sandwich) { tab.setallcaps(true); } else { tab.settext(tab.gettext().tostring().touppercase(locale)); } } if (i == selectedposition) { tab.settextcolor(selectedtabtextcolor); } } } }</span> |
大体就差不多这些了,好了,给大家看一下我自己完善后的样子吧
没有做太多调整，只是稍微的改了一下样式，里面还有一些比较细节的东西没有介绍，比如标题的宽度是平均分配还是分体字体长度进行设置，我们可以修改shouldexpand属性，大家有兴趣的自己仔细研究一下吧.
