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>
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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>
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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>
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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
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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>
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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>
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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>
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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.