Android之路的点点滴滴（补发2017.04.05-2017.04.17这一时间段之二【ViewPager自动轮播】）

自动轮播滚动且一页显示多个Item的ViewPager广告栏

对于我这个新手来说，这个还是有点难度的，需求是实现一个自动轮播切一页显示多个Item的广告栏，因为这个项目是一个只开发平板横版的项目。上网找了好久，大神们的框架都没法设置

android:clipChildren="false"
属性，就不能一页显示多个Item，并且图片的传入方式也不符合我们的需求，所以只好自己来仿写了。

    首先自定义一个ViewPager，如下：

public class AZViewPager extends ViewPager {
    private static AZPagerAdapter mAZPagerAdapter;
    @IntDef({RESUME, PAUSE, DESTROY})
    @Retention(RetentionPolicy.SOURCE)
    public @interface LifeCycle {
    }
    //外部可调用的生命周期常量
    public static final int RESUME = 0;
    public static final int PAUSE = 1;
    public static final int DESTROY = 2;
    /**
     * 生命周期状态，保证{@link #mCarouselTimer}在各生命周期选择执行策略
     */
    private int mLifeCycle = RESUME;
    /**
     * 是否正在触摸状态，用以防止触摸滑动和自动轮播冲突
     */
    private boolean mIsTouching = false;
    /**
     * 轮播定时器
     */
    private ScheduledExecutorService mCarouselTimer;


    public AZViewPager(Context context) {
        super(context);
    }


    public AZViewPager(Context context, AttributeSet attrs) {
        super(context, attrs);
    }
//    外部可调用的设置生命周期的方法
    public void setLifeCycle(@LifeCycle int lifeCycle) {
        this.mLifeCycle = lifeCycle;
    }
    //触摸停止
    @Override
    public boolean onTouchEvent(MotionEvent ev) {
        switch (ev.getAction()) {
            case MotionEvent.ACTION_DOWN:
            case MotionEvent.ACTION_MOVE:
            Log.i("ccc", "运行到触摸判断了");
                mIsTouching = true;
                break;
            case MotionEvent.ACTION_CANCEL:
            case MotionEvent.ACTION_UP:
                mIsTouching = false;
                break;
        }
        return super.onTouchEvent(ev);
    }
    //触发轮播
    @Override
    protected void onAttachedToWindow() {
        super.onAttachedToWindow();
        shutdownTimer();
        mCarouselTimer = Executors.newSingleThreadScheduledExecutor();
        mCarouselTimer.scheduleAtFixedRate(new Runnable() {
            @Override
            public void run() {
                switch (mLifeCycle) {
                    case RESUME:
                        if (!mIsTouching&& getAdapter() != null&& getAdapter().getCount() > 1) {
                            post(new Runnable() {
                                @Override
                                public void run() {
                                    setCurrentItem(getCurrentItem() + 1);
                                }
                            });
                        }
                        break;
                    case PAUSE:
                        break;
                    case DESTROY:
                        shutdownTimer();
                        break;
                }
            }
        }, 1000 * 3, 1000 * 3, TimeUnit.MILLISECONDS);
    }
    //停止轮播
    @Override
    protected void onDetachedFromWindow() {
        super.onDetachedFromWindow();
        shutdownTimer();
    }
    //停止
    private void shutdownTimer() {
        if (mCarouselTimer != null && mCarouselTimer.isShutdown() == false) {
            mCarouselTimer.shutdown();
        }
        mCarouselTimer = null;
    }
}
     再写一个Adapter，实现数据的加载，和监听的设置

public class AZPagerAdapter extends PagerAdapter {


    private AZViewPager mViewPager;
    private Context mContext;
    private List<Banner> bannerList = new ArrayList<>();
    View view = null;


    public AZPagerAdapter(Context context, List<Banner> bannerlist, AZViewPager viewPager) {
        Log.i("aaa", "Adapter中的图案片资源" + bannerlist.size());
        mContext = context;
        this.bannerList = bannerlist;
        this.mViewPager = viewPager;


    }
    //获得图片的个数
    @IntRange(from = 0)
    public int getCountOfVisual() {
        int a = 0;
        if (bannerList != null || bannerList.size() != 0) {
            a = bannerList.size();
        } else {
            a = 0;
        }
        return a;
    }
    //获得总Item数量
    @Override
    public int getCount() {
        return Integer.MAX_VALUE;
    }


    @Override
    public boolean isViewFromObject(View view, Object object) {
        return view == (View) object;
    }


    @Override
    public Object instantiateItem(ViewGroup container, final int position) {
        view = LayoutInflater.from(mContext).inflate(R.layout.fragment_1, null);
        setLayouts(position);
        container.addView(view);
        return view;
    }
    private void setLayouts(int position) {
        Banner banner = bannerList.get(position%getCountOfVisual());
        final ImageView imageView = (ImageView) view.findViewById(R.id.iv_advert_img);
        Glide.with(mContext).load(banner.getBannerLocalPath()).centerCrop().crossFade().into(imageView);
        Log.i("bbb", "拿到image集合" + Glide.with(mContext).load(banner.getBannerLocalPath()).centerCrop().crossFade().into(imageView));


    }
    @Override
    public void destroyItem(ViewGroup container, int position, Object object) {
        container.removeView((View) object);
    }


    @Override
    public void setPrimaryItem(ViewGroup container, int position, Object object) {
        super.setPrimaryItem(container, position, object);
    }


    @Override
    public final void finishUpdate(ViewGroup container) {
        // 数量为1，不做position替换
        if (getCount() <= 1) {
            return;
        }
        int position = mViewPager.getCurrentItem();
        // ViewPager的更新即将完成，替换position，以达到无限循环的效果
        if (position == 0) {
            position = getCountOfVisual();
            mViewPager.setCurrentItem(position, false);
        } else if (position == getCount() - 1) {
            position = getCountOfVisual() - 1;
            mViewPager.setCurrentItem(position, false);
        }
    }
}
	
	自定义一个Indicator指示器：
public class AZIndicatorView extends LinearLayout {
    private int mCount;
    private int mDotDefaultResId;
    private int mDotSelectedResId;
    private int mSelectedPosition;

    public AZIndicatorView(Context context) {
        super(context);
        init(null);
    }

    public AZIndicatorView(Context context, AttributeSet attrs) {
        super(context, attrs);
        init(attrs);
    }

    public AZIndicatorView(Context context, AttributeSet attrs, int defStyleAttr) {
        super(context, attrs, defStyleAttr);
        init(attrs);
    }

    @TargetApi(Build.VERSION_CODES.LOLLIPOP)
    public AZIndicatorView(Context context, AttributeSet attrs, int defStyleAttr, int defStyleRes) {
        super(context, attrs, defStyleAttr, defStyleRes);
        init(attrs);
    }

    private void init(AttributeSet attrs) {
        if (attrs != null) {
            TypedArray typedArray = getContext().obtainStyledAttributes(attrs, R.styleable.AZIndicatorView);
            mCount = typedArray.getInt(R.styleable.AZIndicatorView_dotCount, 0);
            mDotDefaultResId = typedArray.getResourceId(R.styleable.AZIndicatorView_dotDefault, R.drawable.shape_indicator_dot_default);
            mDotSelectedResId = typedArray.getResourceId(R.styleable.AZIndicatorView_dotSelected, R.drawable.shape_indicator_dot_selected);
            mSelectedPosition = typedArray.getInt(R.styleable.AZIndicatorView_dotSelectedPosition, 0);
            typedArray.recycle();
        }
        setOrientation(HORIZONTAL);
        setGravity(Gravity.CENTER);
        initDots();
    }

    private void initDots() {
        int dotMargin = (int) getResources().getDimension(R.dimen.dot_margin);
        for (int i = 0; i < mCount; i++) {
            ImageView dot = new ImageView(getContext());
            dot.setBackgroundResource(i == mSelectedPosition ? mDotSelectedResId : mDotDefaultResId);// 设置引导页默认圆点
            LayoutParams params = new LayoutParams(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
            if (i > 0) {
                params.leftMargin = dotMargin;
            }
            dot.setLayoutParams(params);// 设置圆点的大小
            addView(dot);
        }
    }

    public void setSelectPosition(int selectPosition) {
        if (mCount > 0 && selectPosition > mCount - 1) {
            return;
        }
        this.mSelectedPosition = selectPosition;
        for (int i = 0; i < mCount; i++) {
            getChildAt(i).setBackgroundResource(i == selectPosition ? mDotSelectedResId : mDotDefaultResId);
        }
    }

    public void setCount(int count, int selectPosition) {
        this.mCount = count >= 0 ? count : 0;
        this.mSelectedPosition = selectPosition >= 0 ? selectPosition : 0;
        removeAllViews();
        initDots();
    }
}
	其中需要在Drawable下新建shape_indicator_dot_default.xml和shape_indicator_dot_selected.xml
        shape_indicator_dot_default.xml代码入下：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <solid android:color="#4cffffff" />
    <size
        android:width="@dimen/dot_h"
        android:height="@dimen/dot_h" />
</shape>
	shape_indicator_dot_selected.xml代码如下：
<?xml version="1.0" encoding="utf-8"?>
<shape xmlns:android="http://schemas.android.com/apk/res/android"
    android:shape="oval">
    <solid android:color="@android:color/white" />
    <size
        android:width="@dimen/dot_h"
        android:height="@dimen/dot_h" />
</shape>
	attrs配置文件下添加如下代码：
	
    <declare-styleable name="AZIndicatorView">
        <attr name="dotCount" format="integer" />
        <attr name="dotDefault" format="reference" />
        <attr name="dotSelected" format="reference" />
        <attr name="dotSelectedPosition" format="integer" />
    </declare-styleable>
	dimens文件下添加如下代码：
    <dimen name="dot_margin">4dp</dimen>
    <dimen name="dot_h">8dp</dimen>
	写了这么多，准备工作终于结束了，现在开始写布局文件。
	主XML文件
 <RelativeLayout
        android:id="@+id/rl_advert"
        android:layout_width="match_parent"
        android:layout_height="145dp"
        android:layout_below="@+id/rl_pao_ma_deng"
        android:layout_marginTop="14dp"
        android:clipChildren="false"
        >

        <game.com.mygameboxapp.tools.AZViewPager
            android:id="@+id/vp_advert"
            android:layout_width="585dp"
            android:layout_height="145dp"
            android:layout_centerHorizontal="true"
            android:layout_marginLeft="-400dp"
            android:clipChildren="false"
           ></game.com.mygameboxapp.tools.AZViewPager>

        <game.com.mygameboxapp.tools.AZIndicatorView
        android:id="@+id/banner_indicator"
        android:layout_width="match_parent"
        android:layout_height="15dp"
        android:layout_alignBottom="@id/vp_advert"
        android:layout_centerHorizontal="true"
        android:layout_alignParentBottom="true"/>

    </RelativeLayout>
	
	Item的Xml文件
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical"
    android:layout_marginLeft="50dp"
    android:layout_marginRight="50dp">

    <ImageView
        android:id="@+id/iv_advert_img"
        android:layout_width="585dp"
        android:layout_height="145dp"
        android:background="#00ffffff"
        android:paddingLeft="2dp"
        android:paddingRight="2dp" />


</LinearLayout>
	MainActivity中代码如下。
    private AZViewPager bannerViewPager;
    private AZIndicatorView bannerIndicatorView;
    private AZPagerAdapter bannerPagerAdapter;
	    DBManager dbManager = new DBManager(getBaseContext());
	    List<Banner> bannerList = dbManager.queryBanner();
        bannerPagerAdapter = new AZPagerAdapter(MainActivity.this, bannerList, bannerViewPager);
        bannerViewPager.setAdapter(bannerPagerAdapter);
        bannerIndicatorView.setCount(bannerList.size(), 0);
	    //监听
	    //指示器监听
	    bannerViewPager.addOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
        @Override
        public void onPageSelected(int position) {
          super.onPageSelected(position);
          bannerIndicatorView.setSelectPosition(position % bannerPagerAdapter.getCountOfVisual());
         }
      });
        //轮播点击事件
        bannerViewPager.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {

                return false;
            }
        });
}
@Override
    protected void onResume() {
        super.onResume();
        bannerViewPager.setLifeCycle(AZViewPager.RESUME);
    }

    @Override
    protected void onPause() {
        super.onPause();
        bannerViewPager.setLifeCycle(AZViewPager.PAUSE);
    }

    @Override
    protected void onDestroy() {
        super.onDestroy();
        bannerViewPager.setLifeCycle(AZViewPager.DESTROY);
    }
	其中用到的实体类是这样。
public class Banner {
    public String bannerUrl;
    public String bannerId;
    public String bannerLocalPath;

    public String getBannerId() {
        return bannerId;
    }

    public void setBannerId(String bannerId) {
        this.bannerId = bannerId;
    }

    public String getBannerLocalPath() {
        return bannerLocalPath;
    }

    public void setBannerLocalPath(String bannerLocalPath) {
        this.bannerLocalPath = bannerLocalPath;
    }

    public String getBannerUrl() {
        return bannerUrl;
    }

    public void setBannerUrl(String bannerUrl) {
        this.bannerUrl = bannerUrl;
    }
}
	好了，就是这样了。
	此外，还为此ViewPager添加了调整速度和预加载功能。
	下面是速度调节的类
    public class ViewPagerScroller extends Scroller {
    private int mScrollDuration = 0; // 滑动速度

    /**
     * 设置速度速度
     *
     * @param duration
     */
    public void setScrollDuration(int duration) {
        this.mScrollDuration = duration;
    }

    public ViewPagerScroller(Context context) {
        super(context);
    }

    public ViewPagerScroller(Context context, Interpolator interpolator) {
        super(context, interpolator);
    }

    public ViewPagerScroller(Context context, Interpolator interpolator,
                             boolean flywheel) {
        super(context, interpolator, flywheel);
    }

    @Override
    public void startScroll(int startX, int startY, int dx, int dy, int duration) {
        super.startScroll(startX, startY, dx, dy, mScrollDuration);
    }

    @Override
    public void startScroll(int startX, int startY, int dx, int dy) {
        super.startScroll(startX, startY, dx, dy, mScrollDuration);
    }

    public void initViewPagerScroll(ViewPager viewPager) {
        try {
            Field mScroller = ViewPager.class.getDeclaredField("mScroller");
            mScroller.setAccessible(true);
            mScroller.set(viewPager, this);
        } catch (Exception e) {
            e.printStackTrace();
        }
    }
}
	在Mainactivity中添加如下代码实现速度调节和预加载。
private ViewPagerScroller bannerViewPagerScroller;
bannerViewPagerScroller = new ViewPagerScroller(this);
bannerViewPager.setOffscreenPageLimit(bannerList.size());//设置预加载数量
bannerViewPagerScroller.setScrollDuration(1500);//设置切换速度
bannerViewPagerScroller.initViewPagerScroll(bannerViewPager);