让ViewPager循环起来
自定义ViewPage，支持循环滚动，并在此基础上提供一个图片轮播控件的实现。演示代码：http://download.csdn.net/detail/u012070340/8884565
Java代码import android.content.Context;
import android.os.Handler;
import android.support.v4.view.PagerAdapter;
import android.support.v4.view.ViewPager;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
/**
* Cycle 循环
*/
public class CycleViewPager extends ViewPager {
private PagerAdapter adapter = new PagerAdapter() {
private View cachedHeader, cachedBottom; /* 缓存相关 */
public Object instantiateItem(ViewGroup container, int position) {
View v = null;
if(enabled()) { /* 缓存相关 */
if(position == 1){
if(cachedHeader != null && container.indexOfChild(cachedHeader) == -1){
v = cachedHeader;
}
if(cachedBottom == null || container.indexOfChild(cachedBottom) != -1){
cachedBottom = (View) adapter2.instantiateItem(container, adapter2.getCount() - 1);
}
}else if(position == getCount() - 2){
if(cachedBottom != null && container.indexOfChild(cachedBottom) == -1){
v = cachedBottom;
}
if(cachedHeader == null || container.indexOfChild(cachedHeader) != -1){
cachedHeader = (View) adapter2.instantiateItem(container, 0);
}
}
}
if(v == null){
v = (View) adapter2.instantiateItem(container, convert(position));
}
container.addView(v); // 用户适配器仅负责实例化即可
return v;
}
@Override
public boolean isViewFromObject(View arg0, Object arg1) {
return arg0 == arg1;
}
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((View) object);
}
public int getItemPosition(Object object) {
return adapter2.getItemPosition(object); // 动态更新
}
public void setPrimaryItem(ViewGroup container, int position, Object object) {
if(!edge(position))
adapter2.setPrimaryItem(container, convert(position), object);
}
@Override
public int getCount() {
return enabled() ? adapter2.getCount() + 2 : adapter2 != null ? adapter2.getCount() : 0;
}
}, adapter2;
private OnPageChangeListener listener = new OnPageChangeListener() {
Handler handler = new Handler();
@Override
public void onPageSelected(int position) {
if(listener2 != null && !edge(position))
listener2.onPageSelected(convert(position));
}
@Override
public void onPageScrolled(final int position, final float percent, int offsetPx) {
if(listener2 != null && !edge(position))
listener2.onPageScrolled(convert(position), percent, offsetPx);
if(enabled() && percent == 0){
handler.postDelayed(new Runnable() {
@Override
public void run() {
if(position == 0)
CycleViewPager.super.setCurrentItem(( adapter.getCount() - 2 ) % adapter.getCount(), false); // 切到倒数第二页
else if(position == adapter.getCount() - 1)
CycleViewPager.super.setCurrentItem(1, false); // 切到正数第二页
}
}, 30); // 延迟切换，避免闪烁
}
}
@Override
public void onPageScrollStateChanged(int state) {
if(listener2 != null && !edge(CycleViewPager.super.getCurrentItem()))
listener2.onPageScrollStateChanged(state);
}
}, listener2;
public CycleViewPager(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public CycleViewPager(Context context) {
super(context);
init();
}
private void init() {
super.setAdapter(adapter);
super.setOnPageChangeListener(listener);
}
@Override
public void setAdapter(PagerAdapter adapter) {
this.adapter2 = adapter;
if(enabled())
super.setCurrentItem(1);
this.adapter.notifyDataSetChanged();
}
@Override
public void setOnPageChangeListener(OnPageChangeListener listener) {
this.listener2 = listener;
}
@Override
public void setCurrentItem(int item) {
super.setCurrentItem(enabled() ? item + 1 : item);
}
@Override
public void setCurrentItem(int item, boolean smoothScroll) {
super.setCurrentItem(enabled() ? item + 1 : item, smoothScroll);
}
@Override
public int getCurrentItem() {
return convert(super.getCurrentItem());
}
private int convert(int item){
return enabled() ? item == 0 ? adapter2.getCount() - 1 : ( item > adapter2.getCount() ? 0 : item - 1 ): item;
}
private boolean enabled(){
return adapter2 != null ? adapter2.getCount() > 1 : false;
}
private boolean edge(int position){
return enabled() ? position == 0 || position == adapter.getCount() - 1 : false;
}
}基于此实现的图片轮播控件import android.content.Context;
import android.os.Handler;
import android.os.Message;
import android.support.v4.view.PagerAdapter;
import android.util.AttributeSet;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
public class ImagePager extends CycleViewPager {
private int[] resIds;
private PagerAdapter adapter = new PagerAdapter(){
@Override
public Object instantiateItem(ViewGroup container, int position) {
ImageView iv = new ImageView(getContext());
iv.setImageResource(resIds);
iv.setScaleType(ImageView.ScaleType.FIT_XY);
return iv;
}
@Override
public int getCount() {
return resIds == null ? 0 : resIds.length;
}
@Override
public boolean isViewFromObject(View arg0, Object arg1) {
return false;
}
};
private OnPageChangeListener listener = new OnPageChangeListener(){
@Override
public void onPageScrollStateChanged(int arg0) {
if(listener2 != null){
listener2.onPageScrollStateChanged(arg0);
}
switch (arg0) {
case SCROLL_STATE_IDLE: // 闲置
if(!handler.hasMessages(START_FLIPPING))
handler.sendEmptyMessageDelayed(START_FLIPPING, 3000);// 延时滚动
break;
case SCROLL_STATE_DRAGGING: // 拖动中
handler.sendEmptyMessage(STOP_FLIPPING); // 取消滚动
break;
case SCROLL_STATE_SETTLING: // 拖动结束
break;
}
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {
if(listener2 != null){
listener2.onPageScrolled(arg0, arg1, arg2);
}
}
@Override
public void onPageSelected(int arg0) {
if(listener2 != null){
listener2.onPageSelected(arg0);
}
}
}, listener2;
private final int START_FLIPPING = 0;
private final int STOP_FLIPPING = 1;
private Handler handler = new Handler(){
public void handleMessage(Message msg) {
switch (msg.what) {
case START_FLIPPING:
setCurrentItem(getCurrentItem() + 1);
handler.sendEmptyMessageDelayed(START_FLIPPING, 3000);// 延时滚动
break;
case STOP_FLIPPING:
handler.removeMessages(START_FLIPPING);
break;
}
}
};
public ImagePager(Context context, AttributeSet attrs) {
super(context, attrs);
init();
}
public ImagePager(Context context) {
super(context);
init();
}
private void init(){
setOffscreenPageLimit(1); // 最大页面缓存数量
super.setOnPageChangeListener(listener);
handler.sendEmptyMessageDelayed(START_FLIPPING, 3000);// 自动滚动
}
public void setViews(int[] ids){
this.resIds = ids;
setAdapter(adapter);
}
@Override
public void setOnPageChangeListener(OnPageChangeListener listener) {
this.listener2 = listener;
}
}
Android 的应用 自动循环吗？
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