Android笔记——ViewPager循环、自动滚动效果

/**

• 初始化viewpager
  */
  private void initViewPager() {
  if (mAdapter==null){
  return;
  }
  viewPager.setCurrentItem(currentIndex);
  //设置红缓存的页面数
  viewPager.setOffscreenPageLimit(1);
  // 设置2张图之前的间距。
  viewPager.setPageMargin(pageMargin);
  // viewPager.setPageTransformer(true, new ZoomOutPageTransformer());
  viewPager.addOnPageChangeListener(new ViewPager.OnPageChangeListener() {
  @Override
  public void onPageScrolled(int position, float positionOffset,int positionOffsetPixels) {
  }

@Override
public void onPageSelected(int position) {
if (position0){
currentIndex = mAdapter.getCount()-2 ;
}else if (position == mAdapter.getCount()-1){
currentIndex = 1 ;
}else {
currentIndex = position ;
}
//此处currentIndex是从1开始的，要注意
mLinearLayout.getChildAt(oldPosition).setEnabled(false);
mLinearLayout.getChildAt(currentIndex-1).setEnabled(true);
oldPosition = currentIndex-1 ;
Log.e(“wenzhihao”,"position"+position+“,currentIndex=”+currentIndex);
}

@Override
public void onPageScrollStateChanged(int state) {
if(stateViewPager.SCROLL_STATE_IDLE){
viewPager.setCurrentItem(currentIndex,false);
play();
}else if(stateViewPager.SCROLL_STATE_DRAGGING){
cancel();
}
}
});
setIndicatorDot();
mLinearLayout.getChildAt(0).setEnabled(true);
}

/**

• 播放，根据autoplay
  /
  public void play(){
  if (autoPlay){
  handler.postDelayed(runnable,time);
  }else {
  handler.removeCallbacks(runnable);
  }
  }
  /*
• 取消播放
  */
  public void cancel(){
  handler.removeCallbacks(runnable);
  }

/**

• 设置小圆点
  */
  private void setIndicatorDot() {
  for (int i = 0;i<mAdapter.getCount()-2;i++){
  //添加底部灰点
  View v = new View(mContext);
  v.setBackgroundResource(R.drawable.bg_dot);
  v.setEnabled(false);
  //指定其大小
  LinearLayout.LayoutParams params = new LinearLayout.LayoutParams(20,20);
  if (i != 0)
  params.leftMargin = 20;
  params.bottomMargin = 20;
  v.setLayoutParams(params);
  mLinearLayout.addView(v);
  }
  }

/**

• 设置适配器
• @param adpter
  */
  public void setAdapter(T adpter){
  mAdapter = adpter ;
  viewPager.setAdapter(mAdapter);
  initViewPager();
  }

/**

• 设置是否自动播放
• @param autoPlay
  */
  public void setAutoPlay(boolean autoPlay) {
  AutoScrollViewPager.autoPlay = autoPlay;
  if (!autoPlay){
  handler.removeCallbacks(runnable);
  }
  }
  }

注意主要几点

• 组合控件，一个FrameLayout布局包含ViewPager和一个小圆点指示器。
• 自动循环用handler实现，循环发送消息。
• 这里需要注意的是setAdapter( )方法，只要正常写PageAdapter传入即可;
• 在OnPageChangeListener中，onPageSelected的时候去处理位置问题，就是图中所说的，从左往右滑动，position0的时候切换到4的位置，当从右往左滑动的时候，positon5的时候切换到1的位置。onPageScrollStateChanged状态改变的时候，即停止滑动的时候滑到指定位置，当手指拖动的时候需要停止自动播放；
• 小圆点指示器，是一个线性布局根据图片数量添加原点，原点背景为selector；
• 在屏幕显示的时候设置自动播放，离开屏幕时候停止播放；
• 如果想显示3个page需要在viewpager父容器设置

android:clipChildren=“false”
android:layerType=“hardware”
//代码如下
setLayerType(View.LAYER_TYPE_SOFTWARE, null);
setClipChildren(false);

并且设置viewPager.setPageMargin(pageMargin);，需要加其他特效可以自定义PageTransformer。

• setAutoPlay方法可以设置不自动循环 viewPager.setAutoPlay(false);

例子

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>

<com.wzh.AutoScrollViewPager
android:id=“@+id/viewpager”
android:layout_width=“match_parent”
android:layout_height=“300dp”>
</com.wzh.AutoScrollViewPager>

MainActivity.java

import android.os.Bundle;
import android.support.v7.app.AppCompatActivity;

public class MainActivity extends AppCompatActivity {
private AutoScrollViewPager viewPager ;
private ViewPagerAdapter adapter ;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
viewPager = (AutoScrollViewPager) findViewById(R.id.viewpager);
adapter = new ViewPagerAdapter(this);
viewPager.setAdapter(adapter);
viewPager.setAutoPlay(true);
}

}

ViewPagerAdapter.java

import android.content.Context;
import android.support.v4.view.PagerAdapter;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;

import com.bumptech.glide.Glide;

/**

• Created by WZH on 2018/4/14.
  */

public class ViewPagerAdapter extends PagerAdapter {
private String[] resIds = {
//最后一张图片
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772064849&di=7502440dd81352d3e3d584eb810e0acc&imgtype=0&src=http%3A%2F%2Fimage.tianjimedia.com%2FuploadImages%2F2012%2F265%2F5432CKKPF561_1000x500.jpg”,
//正真的5张图片
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772064850&di=dd3588fdf916fce1527f7b53cc536293&imgtype=0&src=http%3A%2F%2Fimage.tianjimedia.com%2FuploadImages%2F2012%2F088%2F9KF35LBMFO74.jpg”,
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772064854&di=165a16c1167b38b067b3c82cb830c347&imgtype=0&src=http%3A%2F%2Fattachments.gfan.com%2Fforum%2Fattachments2%2F201303%2F18%2F110902j0e5zjwj0yutt00j.jpg”,
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772064877&di=dac68b830070fb6dbf1a9d71fc6b2772&imgtype=0&src=http%3A%2F%2Fi3.download.fd.pchome.net%2Fg1%2FM00%2F0D%2F18%2FoYYBAFS8sGGIUf9wAAJfpTlwpsgAACPGwFaL6cAAl-9928.jpg”,
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772294591&di=9633b23326710637bda3b511c87e0fdb&imgtype=jpg&src=http%3A%2F%2Fimg0.imgtn.bdimg.com%2Fit%2Fu%3D1163084700%2C3470735618%26fm%3D214%26gp%3D0.jpg”,
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772064849&di=7502440dd81352d3e3d584eb810e0acc&imgtype=0&src=http%3A%2F%2Fimage.tianjimedia.com%2FuploadImages%2F2012%2F265%2F5432CKKPF561_1000x500.jpg”,
//第一张图片
“https://timgsa.baidu.com/timg?image&quality=80&size=b9999_10000&sec=1523772064850&di=dd3588fdf916fce1527f7b53cc536293&imgtype=0&src=http%3A%2F%2Fimage.tianjimedia.com%2FuploadImages%2F2012%2F088%2F9KF35LBMFO74.jpg”,
};

private Context context ;
public ViewPagerAdapter(Context context) {
this.context = context ;
}

@Override
public int getCount() {
return resIds.length;
}

@Override
public Object instantiateItem(ViewGroup container, int position) {
View view = View.inflate(context, R.layout.vp_item, null);
ImageView imageView = (ImageView) view.findViewById(R.id.image);
Glide.with(context)
.load(resIds[position])
.into(imageView);
// imageView.setImageResource(resIds[position]);
//添加到容器中
container.addView(view);
return view;
}

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

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

// bg_while.xml

<?xml version="1.0" encoding="utf-8"?>

//bg_gray.xml

<?xml version="1.0" encoding="utf-8"?>

//bg_dot.xml

<?xml version="1.0" encoding="utf-8"?>

效果图

###最后

em android:drawable=“@drawable/bg_while” android:state_enabled=“true” />

效果图

[外链图片转存中…(img-zUDaSPoe-1726634666418)]

[外链图片转存中…(img-CTHgIT2C-1726634666418)]

###最后