在网上找了很多viewpager实现图片轮播的，但是大多数通过以下方式在pageradapter的getcount()返回一个无限大的数，来实现 伪无限
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@override
public int getcount() {
return integer.max_value;//返回一个无限大的值，可以 无限循环
}
虽然通过这种方式是能达到效果，但是从严格意义上来说并不是真正的无限。
假如有五张轮播图 item的编号为（0,1,2,3,4） 要想实现 无限循环 我们在这五张的头部和尾部各加一张即（5+2）张,item编号为（0,1,2,3,4,5,6）其中编号为0,6的两张不做展示只是为了做循环轮播的铺垫，使得播放更加平滑。
1、当我们从编号为5 右滑的时候到了编号6 这时候就将当前页面设置为1
2、当我们从编号为1左滑的时候到了编号0 这时候就将当前页面设置为5
这么做之后就可以实现无限轮播 怎么保证从编号6跳转编号1的时候不出现页面停顿 突然跳到下一页的现象呢？
public object instantiateitem (viewgroup container, int position)
在指定的位置创建页面；适配器负责添加view到这个容器中，然而它只保证在finishupdate(viewgroup)返回时才完成。
public void destroyitem (viewgroup container, int position, object object)
删除指定位置的页面；适配器负责从view容器中删除view，然而它只保证在finishupdate(viewgroup)返回时才完成。
所以说 重点就在于finishupdate(viewgroup)这个方法 其实无论是创建view添加到容器中 还是 销毁view 都是在此方法结束之后执行的
换句话说 就是 我在这个方法里让页面完成从 编号5跳转到编号1 或者从编号1跳转到编号5，此方法完成时 视图还未完成创建或者 销毁 这样也就不会出现 页面停顿 突然跳到下一页的现象。
@override
public void finishupdate(viewgroup container) {
super.finishupdate(container);
int position = viewpager.getcurrentitem();
if (position == 0) {
position = simpledraweeviewlist.size() - 2;
viewpager.setcurrentitem(position,false);
} else if (position == simpledraweeviewlist.size() - 1) {
position = 1;
viewpager.setcurrentitem(position,false);
}
}
话不多说，上代码：
布局文件：
<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.constraintlayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context=".mainactivity">
<framelayout
android:id="@+id/framelayout"
android:layout_width="0dp"
android:layout_height="200dp"
app:layout_constraintend_toendof="parent"
app:layout_constrainthorizontal_bias="0.0"
app:layout_constraintstart_tostartof="parent"
app:layout_constrainttop_totopof="parent">
<android.support.v4.view.viewpager
android:id="@+id/viewpager"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:layout_editor_absolutex="8dp"
tools:layout_editor_absolutey="0dp" />
<linearlayout
android:layout_width="match_parent"
android:layout_height="35dip"
android:layout_gravity="bottom"
android:background="#33000000"
android:gravity="center_vertical"
android:orientation="horizontal"
android:weightsum="10">
<textview
android:id="@+id/tv_pager_title"
android:layout_width="0dp"
android:layout_height="35dip"
android:layout_weight="8"
android:gravity="center_vertical"
android:paddingleft="8dip"
android:text="加载图片轮播失败"
android:textcolor="@android:color/white" />
<linearlayout
android:id="@+id/linelayout_dot"
android:layout_width="0dp"
android:layout_height="match_parent"
android:layout_marginright="5dp"
android:layout_weight="2"
android:gravity="center|right"
android:orientation="horizontal"
android:paddingleft="3dp"
android:paddingright="3dp" />
</linearlayout>
</framelayout>
</android.support.constraint.constraintlayout>
最主要的pageradapter：
import android.content.context;
import android.support.v4.view.pageradapter;
import android.support.v4.view.viewpager;
import android.util.log;
import android.view.view;
import android.view.viewgroup;
import com.facebook.drawee.view.simpledraweeview;
import java.util.list;
public class imagespageradapter extends pageradapter {
private list<simpledraweeview> simpledraweeviewlist;
private viewpager viewpager;
private context context;
private simpledraweeview simpledraweeview;
public imagespageradapter(list<simpledraweeview> simpledraweeviewlist, viewpager viewpager, context context) {
this.simpledraweeviewlist = simpledraweeviewlist;
this.viewpager = viewpager;
this.context = context;
}
@override
public int getcount() {
return simpledraweeviewlist.size();
}
//删除指定位置的页面；适配器负责从view容器中删除view，然而它只保证在finishupdate(viewgroup)返回时才完成。
@override
public void destroyitem(viewgroup container, int position, object object) {
// 把imageview从viewpager中移除掉
viewpager.removeview(simpledraweeviewlist.get(position));
//super.destroyitem(container, position, object);
}
//是否获取缓存
@override
public boolean isviewfromobject(view view, object object) {
return view == object;
}
//实例化item
//在指定的位置创建页面；适配器负责添加view到这个容器中，然而它只保证在finishupdate(viewgroup)返回时才完成。
@override
public object instantiateitem(viewgroup container, int position) {
simpledraweeview = simpledraweeviewlist.get(position);
viewpager.addview(simpledraweeview);
return simpledraweeview;
}
@override
public int getitemposition(object object) {
return position_none;
}
//无论是创建view添加到容器中 还是 销毁view 都是在此方法结束之后执行的
@override
public void finishupdate(viewgroup container) {
super.finishupdate(container);
int position = viewpager.getcurrentitem();
if (position == 0) {
position = simpledraweeviewlist.size() - 2;
viewpager.setcurrentitem(position,false);
} else if (position == simpledraweeviewlist.size() - 1) {
position = 1;
viewpager.setcurrentitem(position,false);
}
}
/* private int mchildcount = 0;
@override
public void notifydatasetchanged() {
mchildcount = getcount();
super.notifydatasetchanged();
}
@override
public int getitemposition(object object) {
if (mchildcount > 0) {
mchildcount--;
log.e("image","getitemposition");
return position_none;
}
return super.getitemposition(object);
}*/
}
import android.app.activity;
import android.content.context;
import android.graphics.drawable.drawable;
import android.support.v4.content.contextcompat;
import android.support.v4.view.viewpager;
import android.util.log;
import android.view.view;
import android.view.viewgroup;
import android.widget.linearlayout;
import android.widget.textview;
import com.facebook.drawee.view.simpledraweeview;
import java.util.arraylist;
import java.util.list;
public class imagecarousel {
private context context;
private viewpager viewpager;
private textview tvtitle;
private linearlayout dotsroot;
private int time;
private list<view> dots;//小点
private int previousposition = 1;//前一个被选中的position
private list<simpledraweeview> simpledraweeviewlist;
private string[] titles;//标题数组
private imagespageradapter adapter;
private autoplaythread autoplaythread;
private volatile boolean isexit = true;
private static final int first_page = 1;
public imagecarousel(context context, viewpager viewpager, textview tvtitle,
list<view> dots, int time) {
this.context = context;
this.viewpager = viewpager;
this.tvtitle = tvtitle;
this.dots = dots;
this.time = time;
log.e("image", "构造方法");
}
/**
* 传入数据
*
* @param simpledraweeviewlist simpledraweeview集合
* @param titles 标题数组
* @return this 本身
*/
public imagecarousel init(list<simpledraweeview> simpledraweeviewlist, string[] titles) {
this.simpledraweeviewlist = simpledraweeviewlist;
this.titles = titles;
log.e("image", "init");
autoplaythread = new autoplaythread();
return this;
}
/**
* 重新加载，有待考验...
*
* @param simpledraweeviewlist simpledraweeview集合
* @param titles 标题数组
*/
public void reload(list<simpledraweeview> simpledraweeviewlist, string[] titles) {
init(simpledraweeviewlist, titles);
previousposition = 0;
start();
}
/**
* 设置设配器，并实现轮播功能
*/
public void start() {
if (adapter != null) {
adapter = null;
}
adapter = new imagespageradapter(this.simpledraweeviewlist, viewpager, context);
viewpager.setadapter(adapter);
viewpager.addonpagechangelistener(new viewpager.onpagechangelistener() {
@override
public void onpagescrolled(int position, float positionoffset, int positionoffsetpixels) {
}
//当被选择
@override
public void onpageselected(int position) {
int currentposition = 1;
if (position == simpledraweeviewlist.size() - 1) {
// 设置当前值为1
currentposition = first_page;
} else if (position == 0) {
// 如果索引值为0了,就设置索引值为倒数第二个
currentposition = simpledraweeviewlist.size() - 2;
} else {
currentposition = position;
}
// 把当前选中的点给切换了, 还有描述信息也切换
tvtitle.settext(titles[currentposition]);//图片下面设置显示文本
//设置轮播点 可设置成传入的图
log.d("dots", "previousposition=" + previousposition + " currentposition=" + currentposition);
dots.get(previousposition-1).setbackgroundresource(r.drawable.ic_dot_focused);
dots.get(currentposition-1).setbackgroundresource(r.drawable.ic_dot_normal);
// 把当前的索引赋值给前一个索引变量, 方便下一次再切换.
previousposition = currentposition;
}
@override
public void onpagescrollstatechanged(int state) {
// scroll_state_idle ：空闲状态
// scroll_state_dragging ：滑动状态
// scroll_state_settling ：滑动后滑翔的状态
if (state == viewpager.scroll_state_dragging) {
} else if(state == viewpager.scroll_state_idle){
}
}
});
setfirstlocation();
//autoplaythread.start();
}
/**
* 设置刚打开app时显示的图片和文字
*/
private void setfirstlocation() {
tvtitle.settext(titles[0]);
dots.get(0).setbackgroundresource(r.drawable.ic_dot_normal);
viewpager.setcurrentitem(1);
}
/**
* 设置是否轮播
*
* @param b
*/
private void setautoplay(boolean b) {
/*if (b && suspendrequested) {
autoplaythread.requestresume();
} else if (!b){
autoplaythread.requestsuspend();
}*/
}
public void stopautoplay() {
if (autoplaythread != null) {
log.e("thrad", "暂停");
isexit = true;
autoplaythread.interrupt();
autoplaythread = null;
}
}
/**
* 请求继续
*/
public void startautoplay() {
log.e("thrad", "开始");
isexit = false;
autoplaythread = null;
autoplaythread = new autoplaythread();
autoplaythread.start();
}
/**
* 自动播放线程，添加暂停和继续方法
*/
class autoplaythread extends thread {
@override
public synchronized void run() {
while (!isexit) {
try {
thread.sleep(time);
} catch (interruptedexception e) {
log.e("thrad", "强制请求退出线程");
break;
}
((activity) context).runonuithread(new runnable() {
@override
public void run() {
viewpager.setcurrentitem(viewpager.getcurrentitem() + 1);
}
});
if (this.interrupted()) {
log.e("thrad", "已经是停止状态了，我要退出了");
break;
}
}
}
}
}
mainactivity.java:
import android.app.activity;
import android.content.context;
import android.graphics.drawable.drawable;
import android.net.uri;
import android.support.v4.content.contextcompat;
import android.support.v4.view.viewpager;
import android.support.v7.app.appcompatactivity;
import android.os.bundle;
import android.view.view;
import android.view.viewgroup;
import android.widget.abslistview;
import android.widget.linearlayout;
import android.widget.textview;
import com.facebook.drawee.backends.pipeline.fresco;
import com.facebook.drawee.backends.pipeline.pipelinedraweecontroller;
import com.facebook.drawee.drawable.scalingutils;
import com.facebook.drawee.generic.genericdraweehierarchy;
import com.facebook.drawee.generic.genericdraweehierarchybuilder;
import com.facebook.drawee.view.simpledraweeview;
import com.facebook.imagepipeline.common.resizeoptions;
import com.facebook.imagepipeline.request.imagerequest;
import com.facebook.imagepipeline.request.imagerequestbuilder;
import java.util.arraylist;
import java.util.list;
public class mainactivity extends appcompatactivity implements view.onclicklistener {
// 图片轮播控件
private viewpager mviewpager;
private textview mtvpagertitle;
private linearlayout mlinelayoutdot;
private imagecarousel imagecarousel;
private list<view> dots;//小点
// 图片数据，包括图片标题、图片链接、数据、点击要打开的网站（点击打开的网页或一些提示指令）
private list<imageinfo> imageinfolist;
@override
protected void oncreate(bundle savedinstancestate) {
super.oncreate(savedinstancestate);
setcontentview(r.layout.activity_main);
initview();
initevent();
imagestart();
}
@override
public void onclick(view v) {
}
/**
* 初始化事件
* 左右多添加一张图片
*/
private void initevent() {
imageinfolist = new arraylist<>();
imageinfolist.add(new imageinfo(1, "图片5，公告5啦啦啦啦", "", "http://e.hiphotos.baidu.com/image/h%3d300/sign=73443062281f95cab9f594b6f9177fc5/72f082025aafa40fafb5fbc1a664034f78f019be.jpg", ""));
imageinfolist.add(new imageinfo(2, "图片1，公告1啦啦啦啦", "", "http://d.hiphotos.baidu.com/image/pic/item/6159252dd42a2834a75bb01156b5c9ea15cebf2f.jpg", ""));
imageinfolist.add(new imageinfo(3, "图片2，公告2啦啦啦啦", "", "http://c.hiphotos.baidu.com/image/h%3d300/sign=cfce96dfa251f3dedcb2bf64a4eff0ec/4610b912c8fcc3ce912597269f45d688d43f2039.jpg", ""));
imageinfolist.add(new imageinfo(4, "图片3，公告3啦啦啦啦", "", "http://e.hiphotos.baidu.com/image/pic/item/6a600c338744ebf85ed0ab2bd4f9d72a6059a705.jpg", ""));
imageinfolist.add(new imageinfo(5, "图片4，公告4啦啦啦啦", "", "http://b.hiphotos.baidu.com/image/h%3d300/sign=8ad802f3801001e9513c120f880e7b06/a71ea8d3fd1f4134be1e4e64281f95cad1c85efa.jpg", ""));
imageinfolist.add(new imageinfo(6, "图片5，公告5啦啦啦啦", "", "http://e.hiphotos.baidu.com/image/h%3d300/sign=73443062281f95cab9f594b6f9177fc5/72f082025aafa40fafb5fbc1a664034f78f019be.jpg", ""));
imageinfolist.add(new imageinfo(7, "图片1，公告1啦啦啦啦", "", "http://d.hiphotos.baidu.com/image/pic/item/6159252dd42a2834a75bb01156b5c9ea15cebf2f.jpg", ""));
}
/**
* 初始化控件
*/
private void initview() {
mviewpager = findviewbyid(r.id.viewpager);
mtvpagertitle = findviewbyid(r.id.tv_pager_title);
mlinelayoutdot = findviewbyid(r.id.linelayout_dot);
}
private void imagestart() {
//设置图片轮播
int[] imgaeids = new int[]{r.id.pager_image1, r.id.pager_image2, r.id.pager_image3, r.id.pager_image4,
r.id.pager_image5, r.id.pager_image6, r.id.pager_image7, r.id.pager_image8};
string[] titles = new string[imageinfolist.size()];
list<simpledraweeview> simpledraweeviewlist = new arraylist<>();
for (int i = 0; i < imageinfolist.size(); i++) {
titles[i] = imageinfolist.get(i).gettitle();
simpledraweeview simpledraweeview = new simpledraweeview(this);
simpledraweeview.setaspectratio(1.78f);
// 设置一张默认的图片
genericdraweehierarchy hierarchy = new genericdraweehierarchybuilder(this.getresources())
.setplaceholderimage(contextcompat.getdrawable(this, r.drawable.defult), scalingutils.scaletype.center_crop).build();
simpledraweeview.sethierarchy(hierarchy);
simpledraweeview.setlayoutparams(new abslistview.layoutparams(abslistview.layoutparams.match_parent, abslistview.layoutparams.wrap_content));
//加载高分辨率图片;
imagerequest imagerequest = imagerequestbuilder.newbuilderwithsource(uri.parse(imageinfolist.get(i).getimage()))
.setresizeoptions(new resizeoptions(1280, 720))
.build();
pipelinedraweecontroller controller = (pipelinedraweecontroller) fresco.newdraweecontrollerbuilder()
//.setlowresimagerequest(imagerequest.fromuri(uri.parse(listitembean.test_pic_low))) //在加载高分辨率图片之前加载低分辨率图片
.setimagerequest(imagerequest)
.setoldcontroller(simpledraweeview.getcontroller())
.build();
simpledraweeview.setcontroller(controller);
simpledraweeview.setid(imgaeids[i]);//给view设置id
simpledraweeview.settag(imageinfolist.get(i));
simpledraweeview.setonclicklistener(this);
titles[i] = imageinfolist.get(i).gettitle();
simpledraweeviewlist.add(simpledraweeview);
}
dots = adddots(mlinelayoutdot, fromrestodrawable(this, r.drawable.ic_dot_focused), simpledraweeviewlist.size());
imagecarousel = new imagecarousel(this, mviewpager, mtvpagertitle, dots, 5000);
imagecarousel.init(simpledraweeviewlist, titles)
.startautoplay();
imagecarousel.start();
}
/**
* 动态添加一个点
*
* @param linearlayout 添加到linearlayout布局
* @param backgount 设置
* @return 小点的id
*/
private int adddot(final linearlayout linearlayout, drawable backgount) {
final view dot = new view(this);
linearlayout.layoutparams dotparams = new linearlayout.layoutparams(viewgroup.layoutparams.match_parent,
viewgroup.layoutparams.wrap_content);
dotparams.width = 16;
dotparams.height = 16;
dotparams.setmargins(4, 0, 4, 0);
dot.setlayoutparams(dotparams);
dot.setbackground(backgount);
dot.setid(view.generateviewid());
((activity) this).runonuithread(new runnable() {
@override
public void run() {
linearlayout.addview(dot);
}
});
return dot.getid();
}
/**
* 资源图片转drawable
*
* @param context 上下文
* @param resid 资源id
* @return 返回drawable图像
*/
public static drawable fromrestodrawable(context context, int resid) {
return contextcompat.getdrawable(context, resid);
}
/**
* 添加多个轮播小点到横向线性布局
*
* @param linearlayout 线性横向布局
* @param backgount 小点资源图标
* @param number 数量
* @return 返回小点view集合
*/
private list<view> adddots(final linearlayout linearlayout, drawable backgount, int number) {
list<view> dots = new arraylist<>();
for (int i = 2; i < number; i++) { // 注意这里的 i 从 2 开始，只画出5个点
int dotid = adddot(linearlayout, backgount);
dots.add(findviewbyid(dotid));
}
return dots;
}
}
ic_dot_focused.xml：
<vector android:height="5dp" android:viewportheight="24.0" android:viewportwidth="24.0" android:width="5dp" xmlns:android="http://schemas.android.com/apk/res/android"> <path android:fillcolor="#c8ffffff" android:pathdata="m12,12m-8,0a8,8 0,1 1,16 0a8,8 0,1 1,-16 0"/> </vector>
ic_dot_normal.xml：
<vector android:height="5dp" android:viewportheight="24.0" android:viewportwidth="24.0" android:width="5dp" xmlns:android="http://schemas.android.com/apk/res/android"> <path android:fillcolor="#c8fd8888" android:pathdata="m12,12m-8,0a8,8 0,1 1,16 0a8,8 0,1 1,-16 0"/> </vector>
当然这里主要是实现真正的无限轮播，其中对于 用户手动滑动图片时需要暂停轮播没有做相关处理。
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移动技术网。
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