书到用时方恨少，技术到讲时才发现自己是真的会了、还是只是代码的搬运工。
现在APP首页上会有很多使用图片轮播的功能。同时，在包含底部菜单的情况使用图片轮播既是对手机内存的考验，也是对技术的一次摸底。
好了，废话不多说。
现在关于图片轮播，
网上的大多数方案是Thread+Handler 睡眠模式，那今天我们来了解的是一个定义好了通用方式下的单线程池+Handler模式
其中图片的加载我们使用的是Fresco ,当然你也可以试用一下Picasso或Glide
接下来，我们直接上代码
/**
* 广告轮播 Created by zaric on 2016/5/17.
*/
public class Advert {
private ScheduledExecutorService mScheduledExecutorService;
private AdvertRunnable mAdvertRunnable;
private int mPicNum = 0;
private int mSize = 0;
private ViewPager mViewPager;
private Context mCtx;
private ArrayList<SimpleDraweeView> mAdList;
private ArrayList<String> mAdUrlList;
private ArrayList<Integer> mAdLocalList;
private ViewGroup mDotVg;
private AdvertHandler mAdvertHandler;
private boolean isStart = false;
private boolean isLocal = false;
/**
* 装点点的ImageView数组
*/
private ImageView[] mTips;
public Advert(BaseActivity baseActivity) {
this.mCtx = baseActivity;
mViewPager = (ViewPager) baseActivity.findViewById(R.id.advertVp);
mDotVg = (ViewGroup) baseActivity.findViewById(R.id.dotVg);
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int
positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
mAdvertHandler.setTipsSelected(position);
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
public Advert(View view) {
this.mCtx = view.getContext();
mViewPager = (ViewPager) view.findViewById(R.id.advertVp);
mDotVg = (ViewGroup) view.findViewById(R.id.dotVg);
mViewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
@Override
public void onPageScrolled(int position, float positionOffset, int
positionOffsetPixels) {
}
@Override
public void onPageSelected(int position) {
mAdvertHandler.setTipsSelected(position);
}
@Override
public void onPageScrollStateChanged(int state) {
}
});
}
private void init() {
mAdList = new ArrayList<>();
if (mAdUrlList != null && mAdUrlList.size() > 0) {
mSize = mAdUrlList.size();
for (int i = 0; i < mSize; i++) {
String path = mAdUrlList.get(i);
if (TextUtils.isEmpty(path)) {
return;
}
SimpleDraweeView simpleDraweeView = new SimpleDraweeView(mCtx);
simpleDraweeView.setScaleType(ImageView.ScaleType.FIT_XY);
Uri uri = Uri.parse(path);
simpleDraweeView.setImageURI(uri);
mAdList.add(simpleDraweeView);
}
} else {
if (mAdLocalList != null && mAdLocalList.size() > 0) {
mSize = mAdLocalList.size();
for (int i = 0; i < mSize; i++) {
int resId = mAdLocalList.get(i);
if (resId <= 0) {
return;
}
SimpleDraweeView simpleDraweeView = new SimpleDraweeView(mCtx);
simpleDraweeView.setScaleType(ImageView.ScaleType.FIT_XY);
simpleDraweeView.setBackgroundResource(resId);
mAdList.add(simpleDraweeView);
}
}
}
initTips();
mScheduledExecutorService = Executors.newSingleThreadScheduledExecutor();
mAdvertRunnable = new AdvertRunnable();
mAdvertHandler = new AdvertHandler(mViewPager, mTips);
AdvertAdapter advertAdapter = new AdvertAdapter(mAdList);
mViewPager.setAdapter(advertAdapter);
mViewPager.setCurrentItem(0);
}
/**
* 初始化
*/
public void initNet(ArrayList<String> adUrlList) {
isLocal = false;
mAdUrlList = adUrlList;
init();
}
/**
* 开始广告播放
*/
public void startPlay() {
// initialDelay 每隔多少秒执行一次
// period 周期
isStart = true;
mScheduledExecutorService.scheduleAtFixedRate(mAdvertRunnable, 1, isLocal ? mAdLocalList
.size() : mAdUrlList.size(), TimeUnit.SECONDS);
}
/**
* 按秒循环执行本地图片广告
*/
public void initLocal(ArrayList<Integer> adLocalList) {
isLocal = true;
mAdLocalList = adLocalList;
init();
}
public boolean isStart() {
return isStart;
}
/**
* 停止广告轮播
*/
public void stopPlay() {
if (mScheduledExecutorService != null) {
isStart = false;
mScheduledExecutorService.shutdownNow();
}
}
public void destroy() {
if (mAdList != null) {
mAdList.clear();
}
if (mTips != null) {
mTips = null;
}
if (mAdUrlList != null) {
mAdUrlList.clear();
}
}
/**
* 图片轮播热点
*/
private void initTips() {
//将点点加入到ViewGroup中
mTips = null;
mDotVg.removeAllViews();
mTips = new ImageView[mSize];
for (int i = 0, length = mTips.length; i < length; i++) {
ImageView imageView = new ImageView(mCtx);
imageView.setLayoutParams(new ViewGroup.LayoutParams(20, 20));
mTips[i] = imageView;
if (i == 0) {
mTips[i].setImageResource(R.drawable.dot_selected);
} else {
mTips[i].setImageResource(R.drawable.dot_unselected);
}
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(new ViewGroup
.LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
layoutParams.leftMargin = 10;
layoutParams.rightMargin = 10;
mDotVg.addView(imageView, layoutParams);
}
}
private class AdvertRunnable implements Runnable {
@Override
public void run() {
mPicNum = (mPicNum + 1) % mSize;
Message msg = mAdvertHandler.obtainMessage();
msg.arg1 = mPicNum;
msg.sendToTarget();
}
}
private static class AdvertHandler extends Handler {
private WeakReference<ViewPager> mWeakVp;
private WeakReference<ImageView[]> mWeakIv;
public AdvertHandler(ViewPager viewPager, ImageView[] tips) {
mWeakVp = new WeakReference<>(viewPager);
mWeakIv = new WeakReference<>(tips);
}
@Override
public void handleMessage(Message msg) {
super.handleMessage(msg);
if (msg == null) {
return;
}
ViewPager mVp = mWeakVp.get();
if (mVp == null) {
return;
}
int picNum = msg.arg1;
mVp.setCurrentItem(picNum);
setTipsSelected(picNum);
}
/**
* 设置选中的tip的背景
*
* @param selectItems 选中项
*/
public void setTipsSelected(int selectItems) {
ImageView[] mTips = mWeakIv.get();
if (mTips == null) {
return;
}
for (int i = 0, length = mTips.length; i < length; i++) {
if (i == selectItems) {
mTips[i].setImageResource(R.drawable.dot_selected);
} else {
mTips[i].setImageResource(R.drawable.dot_unselected);
}
}
}
}
}
/** * 广告轮播适配器 * Created by zaric on 2016/5/17. */ public class AdvertAdapter extends PagerAdapter { private ArrayList<SimpleDraweeView> mList; public AdvertAdapter(ArrayList<SimpleDraweeView> mList){ this.mList=mList; } @Override public int getCount() { return mList!=null&&mList.size()>0?mList.size():0; } @Override public boolean isViewFromObject(View view, Object object) { return view.equals(object); } @Override public Object instantiateItem(ViewGroup container, int position) { container.addView(mList.get(position)); return mList.get(position); } @Override public void destroyItem(ViewGroup container, int position, Object object) { try { container.removeView(mList.get(position)); } catch (IndexOutOfBoundsException e) { e.printStackTrace(); } } /** * 修改ViewPager自带缓存的BUG */ private int mChildCount = 0; @Override public void notifyDataSetChanged() { mChildCount = getCount(); super.notifyDataSetChanged(); } @Override public int getItemPosition(Object object) { if ( mChildCount > 0) { mChildCount --; return POSITION_NONE; } return super.getItemPosition(object); } }
下面是使用到的布局
<?xml version="1.0" encoding="utf-8"?> <RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent" android:layout_height="wrap_content" > <android.support.v4.view.ViewPager android:id="@+id/advertVp" android:layout_width="match_parent" android:layout_height="130dp" android:fadingEdge="none" /> <LinearLayout android:id="@+id/dotVg" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignBottom="@+id/advertVp" android:layout_centerHorizontal="true" android:layout_marginBottom="5dp" android:gravity="center_vertical" android:orientation="horizontal"/> </RelativeLayout>
那么接下来，我们就来来看看如何使用吧
首先，在需要广告轮播的布局页面中，添加
<include layout="@layout/layout_advert"/>
对应页面的代码中，Fragment 下
private Advert advert; private ArrayList<Integer> localImg ;
localImg = new ArrayList<>(); localImg.add(R.drawable.bg_splash); localImg.add(R.drawable.bg_splash); localImg.add(R.drawable.bg_splash); advert = new Advert(getView()); advert.initLocal(localImg); advert.startPlay();
好了，到此结束了，至于原理和思想的话，欢迎大家一起讨论
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