平时开发软件的时候，经常会碰到轮播图这样的需求，下面介绍一种轮播图的实现方式：
我把轮播图写成了一个自定义控件，需要集成Android Support Library v4包和谷歌推荐的一个图片加载库Glide：
import java.lang.reflect.Field;
import java.util.ArrayList;
import java.util.List;
import android.content.Context;
import android.content.res.TypedArray;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.GradientDrawable;
import android.graphics.drawable.LayerDrawable;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.view.animation.Interpolator;
import android.widget.ImageView;
import android.widget.LinearLayout;
import android.widget.RelativeLayout;
import android.widget.Scroller;
import com.bumptech.glide.Glide;
public class BannerLayout extends RelativeLayout {
private ViewPager pager;
// 指示器容器
private LinearLayout indicatorContainer;
// 未选中图片样式
private Drawable unSelectedDrawable;
// 当前选中图片样式
private Drawable selectedDrawable;
private int WHAT_AUTO_PLAY = 1000;
// 是否自动轮播
private boolean isAutoPlay = true;
private int itemCount;
private int selectedIndicatorColor = 0xffff0000;
private int unSelectedIndicatorColor = 0x88888888;
private Shape indicatorShape = Shape.oval;
private int selectedIndicatorHeight = 6;
private int selectedIndicatorWidth = 6;
private int unSelectedIndicatorHeight = 6;
private int unSelectedIndicatorWidth = 6;
private Position indicatorPosition = Position.centerBottom;
// 轮播的间隔时间
private int autoPlayDuration = 4000;
private int scrollDuration = 900;
private int indicatorSpace = 3;
private int indicatorMargin = 10;
private int defaultImage;
// 指示器的样式
private enum Shape {
rect, oval
}
// 指示器的位置
private enum Position {
centerBottom, rightBottom, leftBottom, centerTop, rightTop, leftTop
}
private OnBannerItemClickListener onBannerItemClickListener;
private Handler handler = new Handler(new Handler.Callback() {
@Override
public boolean handleMessage(Message msg) {
if (msg.what == WHAT_AUTO_PLAY) {
if (pager != null) {
pager.setCurrentItem(pager.getCurrentItem() + 1, true);
handler.sendEmptyMessageDelayed(WHAT_AUTO_PLAY,
autoPlayDuration);
}
}
return false;
}
});
public BannerLayout(Context context) {
super(context);
init(null, 0);
}
public BannerLayout(Context context, AttributeSet attrs) {
super(context, attrs);
init(attrs, 0);
}
public BannerLayout(Context context, AttributeSet attrs, int defStyleAttr) {
super(context, attrs, defStyleAttr);
init(attrs, defStyleAttr);
}
private void init(AttributeSet attrs, int defStyle) {
TypedArray array = getContext().obtainStyledAttributes(attrs,
R.styleable.BannerLayoutStyle, defStyle, 0);
selectedIndicatorColor = array.getColor(
R.styleable.BannerLayoutStyle_selectedIndicatorColor,
selectedIndicatorColor);
unSelectedIndicatorColor = array.getColor(
R.styleable.BannerLayoutStyle_unSelectedIndicatorColor,
unSelectedIndicatorColor);
int shape = array.getInt(R.styleable.BannerLayoutStyle_indicatorShape,
Shape.oval.ordinal());
for (Shape shape1 : Shape.values()) {
if (shape1.ordinal() == shape) {
indicatorShape = shape1;
break;
}
}
selectedIndicatorHeight = (int) array.getDimension(
R.styleable.BannerLayoutStyle_selectedIndicatorHeight,
selectedIndicatorHeight);
selectedIndicatorWidth = (int) array.getDimension(
R.styleable.BannerLayoutStyle_selectedIndicatorWidth,
selectedIndicatorWidth);
unSelectedIndicatorHeight = (int) array.getDimension(
R.styleable.BannerLayoutStyle_unSelectedIndicatorHeight,
unSelectedIndicatorHeight);
unSelectedIndicatorWidth = (int) array.getDimension(
R.styleable.BannerLayoutStyle_unSelectedIndicatorWidth,
unSelectedIndicatorWidth);
int position = array.getInt(
R.styleable.BannerLayoutStyle_indicatorPosition,
Position.centerBottom.ordinal());
for (Position position1 : Position.values()) {
if (position == position1.ordinal()) {
indicatorPosition = position1;
}
}
indicatorSpace = (int) array.getDimension(
R.styleable.BannerLayoutStyle_indicatorSpace, indicatorSpace);
indicatorMargin = (int) array.getDimension(
R.styleable.BannerLayoutStyle_indicatorMargin, indicatorMargin);
autoPlayDuration = array.getInt(
R.styleable.BannerLayoutStyle_autoPlayDuration,
autoPlayDuration);
scrollDuration = array.getInt(
R.styleable.BannerLayoutStyle_scrollDuration, scrollDuration);
isAutoPlay = array.getBoolean(R.styleable.BannerLayoutStyle_isAutoPlay,
isAutoPlay);
defaultImage = array.getResourceId(
R.styleable.BannerLayoutStyle_defaultImage, defaultImage);
array.recycle();
// 绘制未选中状态图形
LayerDrawable unSelectedLayerDrawable;
LayerDrawable selectedLayerDrawable;
GradientDrawable unSelectedGradientDrawable;
unSelectedGradientDrawable = new GradientDrawable();
// 绘制选中状态图形
GradientDrawable selectedGradientDrawable;
selectedGradientDrawable = new GradientDrawable();
switch (indicatorShape) {
case rect:
unSelectedGradientDrawable.setShape(GradientDrawable.RECTANGLE);
selectedGradientDrawable.setShape(GradientDrawable.RECTANGLE);
break;
case oval:
unSelectedGradientDrawable.setShape(GradientDrawable.OVAL);
selectedGradientDrawable.setShape(GradientDrawable.OVAL);
break;
}
unSelectedGradientDrawable.setColor(unSelectedIndicatorColor);
unSelectedGradientDrawable.setSize(unSelectedIndicatorWidth,
unSelectedIndicatorHeight);
unSelectedLayerDrawable = new LayerDrawable(
new Drawable[] { unSelectedGradientDrawable });
unSelectedDrawable = unSelectedLayerDrawable;
selectedGradientDrawable.setColor(selectedIndicatorColor);
selectedGradientDrawable.setSize(selectedIndicatorWidth,
selectedIndicatorHeight);
selectedLayerDrawable = new LayerDrawable(
new Drawable[] { selectedGradientDrawable });
selectedDrawable = selectedLayerDrawable;
}
// 添加本地图片路径
public void setViewRes(List<Integer> viewRes) {
List<View> views = new ArrayList<View>();
itemCount = viewRes.size();
// 主要是解决当item为小于3个的时候滑动有问题，这里将其拼凑成3个以上
if (itemCount < 1) {// 当item个数0
throw new IllegalStateException("item count not equal zero");
} else if (itemCount < 2) {// 当item个数为1
views.add(getImageView(viewRes.get(0), 0));
views.add(getImageView(viewRes.get(0), 0));
views.add(getImageView(viewRes.get(0), 0));
} else if (itemCount < 3) {// 当item个数为2
views.add(getImageView(viewRes.get(0), 0));
views.add(getImageView(viewRes.get(1), 1));
views.add(getImageView(viewRes.get(0), 0));
views.add(getImageView(viewRes.get(1), 1));
} else {
for (int i = 0; i < viewRes.size(); i++) {
views.add(getImageView(viewRes.get(i), i));
}
}
setViews(views);
}
private ImageView getImageView(Integer res, final int position) {
ImageView imageView = new ImageView(getContext());
imageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (onBannerItemClickListener != null) {
onBannerItemClickListener.onItemClick(position);
}
}
});
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
Glide.with(getContext()).load(res).centerCrop().into(imageView);
return imageView;
}
// 添加网络图片路径
public void setViewUrls(List<String> urls) {
List<View> views = new ArrayList<View>();
itemCount = urls.size();
// 主要是解决当item为小于3个的时候滑动有问题，这里将其拼凑成3个以上
if (itemCount < 1) {// 当item个数0
throw new IllegalStateException("item count not equal zero");
} else if (itemCount < 2) { // 当item个数为1
views.add(getImageView(urls.get(0), 0));
views.add(getImageView(urls.get(0), 0));
views.add(getImageView(urls.get(0), 0));
} else if (itemCount < 3) {// 当item个数为2
views.add(getImageView(urls.get(0), 0));
views.add(getImageView(urls.get(1), 1));
views.add(getImageView(urls.get(0), 0));
views.add(getImageView(urls.get(1), 1));
} else {
for (int i = 0; i < urls.size(); i++) {
views.add(getImageView(urls.get(i), i));
}
}
setViews(views);
}
private ImageView getImageView(String url, final int position) {
ImageView imageView = new ImageView(getContext());
imageView.setOnClickListener(new OnClickListener() {
@Override
public void onClick(View v) {
if (onBannerItemClickListener != null) {
onBannerItemClickListener.onItemClick(position);
}
}
});
imageView.setScaleType(ImageView.ScaleType.CENTER_CROP);
if (defaultImage != 0) {
Glide.with(getContext()).load(url).placeholder(defaultImage)
.centerCrop().into(imageView);
} else {
Glide.with(getContext()).load(url).centerCrop().into(imageView);
}
return imageView;
}
// 添加任意View视图
private void setViews(final List<View> views) {
// 初始化pager
pager = new ViewPager(getContext());
// 添加viewpager到SliderLayout
addView(pager);
setSliderTransformDuration(scrollDuration);
// 初始化indicatorContainer
indicatorContainer = new LinearLayout(getContext());
indicatorContainer.setGravity(Gravity.CENTER_VERTICAL);
RelativeLayout.LayoutParams params = new LayoutParams(
LayoutParams.WRAP_CONTENT, LayoutParams.WRAP_CONTENT);
switch (indicatorPosition) {
case centerBottom:
params.addRule(RelativeLayout.CENTER_HORIZONTAL);
params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
break;
case centerTop:
params.addRule(RelativeLayout.CENTER_HORIZONTAL);
params.addRule(RelativeLayout.ALIGN_PARENT_TOP);
break;
case leftBottom:
params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
break;
case leftTop:
params.addRule(RelativeLayout.ALIGN_PARENT_LEFT);
params.addRule(RelativeLayout.ALIGN_PARENT_TOP);
break;
case rightBottom:
params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
params.addRule(RelativeLayout.ALIGN_PARENT_BOTTOM);
break;
case rightTop:
params.addRule(RelativeLayout.ALIGN_PARENT_RIGHT);
params.addRule(RelativeLayout.ALIGN_PARENT_TOP);
break;
}
// 设置margin
params.setMargins(indicatorMargin, indicatorMargin, indicatorMargin,
indicatorMargin);
// 添加指示器容器布局到SliderLayout
addView(indicatorContainer, params);
// 初始化指示器，并添加到指示器容器布局
for (int i = 0; i < itemCount; i++) {
ImageView indicator = new ImageView(getContext());
indicator.setLayoutParams(new ViewGroup.LayoutParams(
ViewGroup.LayoutParams.WRAP_CONTENT,
ViewGroup.LayoutParams.WRAP_CONTENT));
indicator.setPadding(indicatorSpace, indicatorSpace,
indicatorSpace, indicatorSpace);
indicator.setImageDrawable(unSelectedDrawable);
indicatorContainer.addView(indicator);
}
LoopPagerAdapter pagerAdapter = new LoopPagerAdapter(views);
pager.setAdapter(pagerAdapter);
// 设置当前item到Integer.MAX_VALUE中间的一个值，看起来像无论是往前滑还是往后滑都是ok的
// 如果不设置，用户往左边滑动的时候已经划不动了
int targetItemPosition = Integer.MAX_VALUE / 2 - Integer.MAX_VALUE / 2
% itemCount;
pager.setCurrentItem(targetItemPosition);
switchIndicator(targetItemPosition % itemCount);
pager.setOnPageChangeListener(new ViewPager.SimpleOnPageChangeListener() {
@Override
public void onPageSelected(int position) {
switchIndicator(position % itemCount);
}
});
startAutoPlay();
}
public void setSliderTransformDuration(int duration) {
try {
Field mScroller = ViewPager.class.getDeclaredField("mScroller");
mScroller.setAccessible(true);
FixedSpeedScroller scroller = new FixedSpeedScroller(
pager.getContext(), null, duration);
mScroller.set(pager, scroller);
} catch (Exception e) {
e.printStackTrace();
}
}
/**
* 开始自动轮播
*/
public void startAutoPlay() {
stopAutoPlay(); // 避免重复消息
if (isAutoPlay) {
handler.sendEmptyMessageDelayed(WHAT_AUTO_PLAY, autoPlayDuration);
}
}
@Override
protected void onWindowVisibilityChanged(int visibility) {
super.onWindowVisibilityChanged(visibility);
if (visibility == VISIBLE) {
startAutoPlay();
} else {
stopAutoPlay();
}
}
/**
* 停止自动轮播
*/
public void stopAutoPlay() {
if (isAutoPlay) {
handler.removeMessages(WHAT_AUTO_PLAY);
}
}
@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
switch (ev.getAction()) {
case MotionEvent.ACTION_DOWN:
stopAutoPlay();
break;
case MotionEvent.ACTION_CANCEL:
case MotionEvent.ACTION_UP:
startAutoPlay();
break;
}
return super.dispatchTouchEvent(ev);
}
/**
* 切换指示器状态
*
* @param currentPosition
* 当前位置
*/
private void switchIndicator(int currentPosition) {
for (int i = 0; i < indicatorContainer.getChildCount(); i++) {
((ImageView) indicatorContainer.getChildAt(i))
.setImageDrawable(i == currentPosition ? selectedDrawable
: unSelectedDrawable);
}
}
public void setOnBannerItemClickListener(
OnBannerItemClickListener onBannerItemClickListener) {
this.onBannerItemClickListener = onBannerItemClickListener;
}
public interface OnBannerItemClickListener {
void onItemClick(int position);
}
public class LoopPagerAdapter extends PagerAdapter {
private List<View> views;
public LoopPagerAdapter(List<View> views) {
this.views = views;
}
@Override
public int getCount() {
// Integer.MAX_VALUE = 2147483647
return Integer.MAX_VALUE;
}
@Override
public boolean isViewFromObject(View view, Object object) {
return view == object;
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
if (views.size() > 0) {
// position % view.size()是指虚拟的position会在[0，view.size()）之间循环
View view = views.get(position % views.size());
if (container.equals(view.getParent())) {
container.removeView(view);
}
container.addView(view);
return view;
}
return null;
}
@Override
public void destroyItem(ViewGroup container, int position, Object object) {
}
}
public class FixedSpeedScroller extends Scroller {
private int mDuration = 1000;
public FixedSpeedScroller(Context context) {
super(context);
}
public FixedSpeedScroller(Context context, Interpolator interpolator) {
super(context, interpolator);
}
public FixedSpeedScroller(Context context, Interpolator interpolator,
int duration) {
this(context, interpolator);
mDuration = duration;
}
@Override
public void startScroll(int startX, int startY, int dx, int dy,
int duration) {
// Ignore received duration, use fixed one instead
super.startScroll(startX, startY, dx, dy, mDuration);
}
@Override
public void startScroll(int startX, int startY, int dx, int dy) {
// Ignore received duration, use fixed one instead
super.startScroll(startX, startY, dx, dy, mDuration);
}
}
}
自定义控件的属性定义：
<resources>
<declare-styleable name="BannerLayoutStyle">
<attr name="selectedIndicatorColor" format="color|reference" />
<attr name="unSelectedIndicatorColor" format="color|reference" />
<attr name="indicatorShape" format="enum">
<enum name="rect" value="0" />
<enum name="oval" value="1" />
</attr>
<attr name="selectedIndicatorHeight" format="dimension|reference" />
<attr name="selectedIndicatorWidth" format="dimension|reference" />
<attr name="unSelectedIndicatorHeight" format="dimension|reference" />
<attr name="unSelectedIndicatorWidth" format="dimension|reference" />
<attr name="indicatorPosition" format="enum">
<enum name="centerBottom" value="0" />
<enum name="rightBottom" value="1" />
<enum name="leftBottom" value="2" />
<enum name="centerTop" value="3" />
<enum name="rightTop" value="4" />
<enum name="leftTop" value="5" />
</attr>
<attr name="indicatorSpace" format="dimension|reference" />
<attr name="indicatorMargin" format="dimension|reference" />
<attr name="autoPlayDuration" format="integer|reference" />
<attr name="scrollDuration" format="integer|reference" />
<attr name="isAutoPlay" format="boolean"/>
<attr name="defaultImage" format="integer|reference"/>
</declare-styleable>
</resources>
轮播图控件的使用：
BannerLayout bannerLayout = (BannerLayout) findViewById(R.id.banner);
BannerLayout bannerLayout2 = (BannerLayout) findViewById(R.id.banner2);
// 加载网络图片
final List<String> urls = new ArrayList<String>();
urls.add("http://img4.duitang.com/uploads/item/201408/30/20140830185433_FnJLA.jpeg");
urls.add("http://img0.imgtn.bdimg.com/it/u=3379522155,2601893953&fm=21&gp=0.jpg");
urls.add("http://img3.imgtn.bdimg.com/it/u=3269141824,887330507&fm=21&gp=0.jpg");
urls.add("http://img4.imgtn.bdimg.com/it/u=3099510203,1072263599&fm=21&gp=0.jpg");
urls.add("http://img4.imgtn.bdimg.com/it/u=2943793272,3641314298&fm=21&gp=0.jpg");
bannerLayout.setViewUrls(urls);
// 添加监听事件
bannerLayout
.setOnBannerItemClickListener(new BannerLayout.OnBannerItemClickListener() {
@Override
public void onItemClick(int position) {
Toast.makeText(MainActivity.this,
String.valueOf(position), Toast.LENGTH_SHORT)
.show();
}
});
// 低于三张，加载本地图片
final List<Integer> urls2 = new ArrayList<Integer>();
urls2.add(R.drawable.loading_bg_guid1);
urls2.add(R.drawable.loading_bg_guid2);
bannerLayout2.setViewRes(urls2);