android 图片轮播

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1、android 图片轮播主要采用android.support.v4.view.ViewPager

2、android 图片轮播页面分析

3、准备布局文件

①viewpager ：在包下找到view---》ViewPager.class,打开ViewPager.class(若打不开，则去关联源码，源码位置在Androidsdk目录下的extras\android\support\v4)复制包名+类名

②小圆点准备：在资源文件中新建文件夹drawable，，新建两个Android xml文件，下面是point_r.xml的文件内容，point_r.xml文件与其类似，只是颜色有差异。

<?xml version="1.0" encoding="utf-8"?><!--android:shape=["rectangle" | "oval" | "line" | "ring"] shape的形状，默认为矩形，可以设置为矩形（rectangle）、椭圆形(oval)、线性形状(line)、环形(ring)  --><shape xmlns:android="http://schemas.android.com/apk/res/android"    android:shape="oval" ><!-- 半径 -->    <corners android:radius="5dp" /><!-- 白色 -->    <solid android:color="@android:color/white" /></shape>

4、activity_main.xml布局文件

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    tools:context="com.kp.viewpage.MainActivity$PlaceholderFragment" >    <RelativeLayout        android:layout_width="match_parent"        android:layout_height="180dp" >        <android.support.v4.view.ViewPager            android:id="@+id/pageid"            android:layout_width="match_parent"            android:layout_height="180dp" />        <LinearLayout            android:layout_width="match_parent"            android:layout_height="wrap_content"            android:layout_alignParentBottom="true"            android:background="#33000000"            android:orientation="vertical"            android:padding="5dp" >            <TextView                android:id="@+id/tvid"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center_horizontal"                android:text="图片1"                android:textColor="@android:color/white" />            <LinearLayout                android:id="@+id/LinearLayoutPoint"                android:layout_width="wrap_content"                android:layout_height="wrap_content"                android:layout_gravity="center_horizontal"                android:layout_marginTop="5dp"                android:orientation="horizontal" >                <!-- <View                    android:layout_width="10dp"                    android:layout_height="10dp"                    android:layout_marginRight="5dp"                    android:background="@drawable/point_w" />                <View                    android:layout_width="10dp"                    android:layout_height="10dp"                    android:background="@drawable/point_r" /> -->            </LinearLayout>        </LinearLayout>    </RelativeLayout></RelativeLayout>

5、java 代码

package com.kp.viewpage;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.os.Bundle;import android.support.v4.view.PagerAdapter;import android.support.v4.view.ViewPager;import android.support.v4.view.ViewPager.OnPageChangeListener;import android.view.View;import android.view.ViewGroup;import android.widget.ImageView;import android.widget.ImageView.ScaleType;import android.widget.LinearLayout;import android.widget.LinearLayout.LayoutParams;import android.widget.TextView;public class MainActivity extends Activity implements OnPageChangeListener {   private ViewPager viewPage;//图片数据private List<ImageView> imalist;//包裹圆点的线性布局private LinearLayout linearLayoutPoint;//文本private TextView tvid ;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);//实例化viewPage = (ViewPager) findViewById(R.id.pageid);linearLayoutPoint = (LinearLayout) findViewById(R.id.LinearLayoutPoint);tvid = (TextView) findViewById(R.id.tvid);//准备数据int[] imgs = {R.drawable.ad1,R.drawable.ad2,R.drawable.ad3,R.drawable.ad4,R.drawable.ad5,R.drawable.ad6};imalist = new ArrayList<ImageView>();for (int i = 0; i < imgs.length; i++) {ImageView iv = new ImageView(this);iv.setImageResource(imgs[i]);iv.setScaleType(ScaleType.FIT_XY);imalist.add(iv);View v = new View(this);v.setBackgroundResource(R.drawable.point_w);LayoutParams params = new LayoutParams(10,10);if (i!=0) {//从第二个圆点开始，设置左margin间距params.leftMargin=10;}else{//初始化，第一个圆点为红色v.setBackgroundResource(R.drawable.point_r);}linearLayoutPoint.addView(v, params);  }//类似listview 的操作viewPage.setAdapter(new MyviewPageAdapter());//设置监听器，让activity 实现OnPageChangeListenerviewPage.setOnPageChangeListener(this);//设置view当前显示页面int maxhalf = Integer.MAX_VALUE/2;int d = maxhalf%imalist.size();int item = maxhalf -d;viewPage.setCurrentItem(item);}//自定义适配器class MyviewPageAdapter extends PagerAdapter{        @Overridepublic int getCount() {if (imalist!=null) {//return imalist.size();return Integer.MAX_VALUE;}return 0;}// 标记方法，用来判断缓存标记@Overridepublic boolean isViewFromObject(View view, Object object) {// view:显示的view// object: 标记return view==object;}//初始化缓存@Overridepublic Object instantiateItem(ViewGroup container, int position) {position = position%imalist.size();// position： 要加载的位置ImageView iv = imalist.get(position);// 用来添加要显示的View的viewPage.addView(iv);// 记录缓存标记--return 标记return iv;}//销毁缓存@Overridepublic void destroyItem(ViewGroup container, int position, Object object) {position = position%imalist.size();ImageView iv = imalist.get(position);viewPage.removeView(iv);}}//position  当前位置//positionOffset 偏移百分比    偏移量除以屏幕宽度//positionOffsetPixels  偏移量，最大值为屏幕宽度@Overridepublic void onPageScrolled(int position, float positionOffset,int positionOffsetPixels) {}//页面被选中@Overridepublic void onPageSelected(int position) {position = position%imalist.size();//得到圆点数量int childCount = linearLayoutPoint.getChildCount();for (int i = 0; i < childCount; i++) {//得到每个圆点viewView view = linearLayoutPoint.getChildAt(i);if (i!=position) {//圆点的标识不是当前viewpager所显示的下标view.setBackgroundResource(R.drawable.point_w);} else {tvid.setText("图片"+i);view.setBackgroundResource(R.drawable.point_r);}}}//该state 有三个状态，闲置0，拖动1，固定2；先拖动后固定后闲置  1》2》0@Overridepublic void onPageScrollStateChanged(int state) {}}

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