android使用viewpager计算偏移量实现选项卡功能

本文实例为大家分享了android实现选项卡功能，通过计算偏移量，设置tetxview和imageview的对应值，一些color的值读者自己去补充

实现效果图：

（1）简单写一个主界面的布局activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<linearlayout
 xmlns:android="http://schemas.android.com/apk/res/android"
 android:orientation="vertical"
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:cliptopadding="true"
 android:fitssystemwindows="true"
 android:background="@color/bg_color">

 <linearlayout
 android:layout_width="match_parent"
 android:layout_height="match_parent"
 android:background="@color/bag_gray"
 android:orientation="vertical">

 <linearlayout
  android:layout_width="match_parent"
  android:layout_height="36dp"
  android:background="@android:color/white"
  android:orientation="horizontal"
  android:weightsum="3">

  <textview
  android:id="@+id/tab1_tv"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_gravity="center"
  android:layout_weight="1"
  android:gravity="center"
  android:text="商品"
  android:textcolor="@color/title_bag"
  android:textsize="18sp" />

  <textview
  android:id="@+id/tab2_tv"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_gravity="center"
  android:layout_weight="1"
  android:gravity="center"
  android:text="评价"
  android:textcolor="@color/text_color_context"
  android:textsize="18sp" />
  <textview
  android:id="@+id/tab3_tv"
  android:layout_width="0dp"
  android:layout_height="wrap_content"
  android:layout_gravity="center"
  android:layout_weight="1"
  android:gravity="center"
  android:text="详情"
  android:textcolor="@color/text_color_context"
  android:textsize="18sp" />

 </linearlayout>

 <view
  android:layout_width="match_parent"
  android:layout_height="0.5dp"
  android:background="@color/text_color_context" />
 <view
  android:id="@+id/cursor"
  android:layout_width="50dp"
  android:layout_height="2dp"
  android:layout_marginleft="40dp"
  android:layout_margintop="0dip"
  android:background="@color/title_bag"
  />
 <android.support.v4.view.viewpager
  android:id="@+id/thire_vp"
  android:layout_width="match_parent"
  android:layout_height="match_parent"/>
 </linearlayout>

</linearlayout>

（2）设置viewpager的适配器：fragmentadapter

public class fragmentadapter extends fragmentpageradapter {
 private arraylist<fragment> list;
 fragmentmanager fm;

 public fragmentadapter(fragmentmanager fm, arraylist<fragment> list){
 super(fm);
 this.fm = fm;
 this.list = list;
 }

 @override
 public fragment getitem(int position) {
 return list.get(position);
 }

 @override
 public int getcount() {
 return list.size();
 }
}

（3）然后设置三个fragment，因为有三个选项卡，所以我们新建三个fragment，分别是onefragment、twofragment 、threefragment ，布局的话也需要新建三个，跟fragment一一对应，因为布局过于简单，这里就不写了，简单写一点fragment的代码吧

public class onefragment extends fragment {

 @nullable
 @override
 public view oncreateview(layoutinflater inflater, @nullable viewgroup container, @nullable bundle savedinstancestate) {
 view view = inflater.inflate(r.layout.fragment_one,null);
 return view;
 }
}

（4）在mainactivity中，设置fragment的适配器，设置显示内容，并且做viewpager的事件监听

public class mainactivity extends fragmentactivity implements viewpager.onpagechangelistener,view.onclicklistener{
 private textview tab1tv;
 private textview tab2tv;
 private textview tab3tv;
 private view cursor;
 private viewpager thirdvp;

 private arraylist<fragment> fragmentlist;
 private int offset = 0;
 private int screenwidth = 0;
 private int screenl_3;
 private linearlayout.layoutparams lp;

 @override
 protected void oncreate(@nullable bundle savedinstancestate) {
 super.oncreate(savedinstancestate);
 setcontentview(r.layout.activity_product);

 //绑定控件
 tab1tv = (textview)findviewbyid(r.id.tab1_tv);
 tab2tv = (textview)findviewbyid(r.id.tab2_tv);
 tab3tv = (textview)findviewbyid(r.id.tab3_tv);
 cursor = (view) findviewbyid(r.id.cursor);
 thirdvp = (viewpager) findviewbyid(r.id.thire_vp);

 //获取屏幕宽度
 displaymetrics dm = new displaymetrics();
 getwindowmanager().getdefaultdisplay().getmetrics(dm);
 screenwidth = dm.widthpixels;
 screenl_3 = screenwidth/3; //裁剪3分之1
 lp = (linearlayout.layoutparams)cursor.getlayoutparams();

 fragmentlist = new arraylist<>();
 fragmentlist.add(new onefragment());
 fragmentlist.add(new twofragment());
 fragmentlist.add(new threefragment());

 thirdvp.setadapter(new fragmentadapter(getsupportfragmentmanager(),fragmentlist));
 thirdvp.setcurrentitem(0);
 thirdvp.setoffscreenpagelimit(2);

 thirdvp.setonpagechangelistener(this);
 tab1tv.setonclicklistener(this);
 tab2tv.setonclicklistener(this);
 tab3tv.setonclicklistener(this);
 }

 @override
 public void onpagescrolled(int position, float positionoffset, int positionoffsetpixels) {
 offset = (screenl_3-cursor.getlayoutparams().width)/2;
 log.d("tag", "111----"+position + "--" + positionoffset + "--"
  + positionoffsetpixels);
 final float scale = getresources().getdisplaymetrics().density;
 if (position == 0){
  lp.leftmargin = (int)(positionoffsetpixels/3)+offset;
 }else if(position ==1){
  lp.leftmargin = (int)(positionoffsetpixels/3)+screenl_3+offset;
 }
 cursor.setlayoutparams(lp);
 uptextcolor(position);
 }

 private void uptextcolor(int position){
 if (position==0){
  tab1tv.settextcolor(getresources().getcolor(r.color.title_bag));
  tab2tv.settextcolor(getresources().getcolor(r.color.text_color_context));
  tab3tv.settextcolor(getresources().getcolor(r.color.text_color_context));
 }else if(position==1){
  tab1tv.settextcolor(getresources().getcolor(r.color.text_color_context));
  tab2tv.settextcolor(getresources().getcolor(r.color.title_bag));
  tab3tv.settextcolor(getresources().getcolor(r.color.text_color_context));
 }else if(position==2){
  tab1tv.settextcolor(getresources().getcolor(r.color.text_color_context));
  tab2tv.settextcolor(getresources().getcolor(r.color.text_color_context));
  tab3tv.settextcolor(getresources().getcolor(r.color.title_bag));
 }
 }


 @override
 public void onpageselected(int position) {

 }

 @override
 public void onpagescrollstatechanged(int state) {

 }

 @override
 public void onclick(view view) {
 switch (view.getid()) {
  case r.id.tab1_tv:
  thirdvp.setcurrentitem(0);
  break;
  case r.id.tab2_tv:
  thirdvp.setcurrentitem(1);
  break;
  case r.id.tab3_tv:
  thirdvp.setcurrentitem(2);
  break;
 }
 }
}

以上就是本文的全部内容，希望对大家的学习有所帮助，也希望大家多多支持。