viewpager 简介及大量页面加载的方法推荐
先介绍下父类PagerAdapter，包含主要方法 instantiateItem初始化每个页面的view，这个用的比较少
viewPager = (ViewPager) findViewById(R.id.viewpager);
LayoutInflater inflater=getLayoutInflater();
view1 = inflater.inflate(R.layout.layout1, null);
view2 = inflater.inflate(R.layout.layout2,null);
view3 = inflater.inflate(R.layout.layout3, null);
viewList = new ArrayList<View>();// 将要分页显示的View装入数组中
viewList.add(view1);
viewList.add(view2);
viewList.add(view3);
PagerAdapter pagerAdapter = new PagerAdapter() {
@Override
public boolean isViewFromObject(View arg0, Object arg1) {
return arg0 == arg1;
}
@Override
public int getCount() {
return viewList.size(); //界面总的个数
}
@Override
public void destroyItem(ViewGroup container, int position,
Object object) {
container.removeView(viewList.get(position)); //移除view
}
@Override
public Object instantiateItem(ViewGroup container, int position) {
// TODO Auto-generated method stub
container.addView(viewList.get(position));
return viewList.get(position);
}
};
viewPager.setAdapter(pagerAdapter);
2类FragmentPagerAdapter用于保存少量的view,因为内存不会自行回收
List<Fragment> fragments=new ArrayList<Fragment>();
fragments.add(new Fragment1()); //不同布局的
fragments.add(new Fragment2());
FragAdapter adapter = new FragAdapter(getSupportFragmentManager(), fragments);
ViewPager vp = (ViewPager)findViewById(R.id.viewpager);
vp.setAdapter(adapter);
public class Fragment1 extends Fragment {
@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
Bundle savedInstanceState) {
// 布局初始化 数据加载之类的操作
View view=inflater.inflate(R.layout.layout2, container, false);
return view;
}
}
public class FragAdapter extends FragmentPagerAdapter {
private List<Fragment> mFragments;
public FragAdapter(FragmentManager fm,List<Fragment> fragments) {
super(fm);
// TODO Auto-generated constructor stub
mFragments=fragments;
}
@Override
public Fragment getItem(int arg0) {
// TODO Auto-generated method stub
return mFragments.get(arg0);
}
@Override
public int getCount() {
// TODO Auto-generated method stub
return mFragments.size();
}
}
3，FragmentStatePagerAdapter用于页面多的内存只保留3个界面
ArrayList<Fragment> fragmentList = new ArrayList<Fragment>();
for (int i = 0; i < 280; i++) {
MainFragment first = new MainFragment();
fragmentList.add(first); //布局一样数据不一样的界面
}
wikiAdapter = new MyFrageStatePagerAdapter(getSupportFragmentManager());
wikipediaPager.setAdapter(wikiAdapter);
public class MyFrageStatePagerAdapter extends FragmentStatePagerAdapter {
public MyFrageStatePagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
return MainFragment.newInstance(position); //为了传递当前界面index便于进行初始化
}
@Override
public int getCount() {
return fragmentList.size(); //总的界面数
}
}
//自定义获得界面及传入当前界面的值，初始化界面
public class MainFragment extends Fragment {
private int mNum;
public static MainFragment newInstance(int num) {
MainFragment f = new MainFragment();
Bundle args = new Bundle();
args.putInt("num", num);
f.setArguments(args);
return f;
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mNum = getArguments() != null ? getArguments().getInt("num") : 1;
}
View view;
@Override
public View onCreateView(LayoutInflater inflater,ViewGroup container,Bundle savedInstanceState) {
// TODO Auto-generated method stub
view = inflater.inflate(R.layout.wikipedia_pager_item, container,false);
initView(view,MainActivity.wikiList.get(mNum));
return view;
}
｝
FragmentPagerAdapter 继承自 PagerAdapter。相比通用的 PagerAdapter，该类更专注于每一页均为 Fragment 的情况。如文档所述，该类内的每一个生成的 Fragment 都将保存在内存之中，因此适用于那些相对静态的页，数量也比较少的那种；
如需要处理很多页，数据动态性较大，占用内存多的情况，使用FragmentStatePagerAdapter。
当然PagerAdapter也可以处理很多页面的，用循环队列来节省内存，例子如下
viewpager总是会预加载后面的界面，所以要让控件本身去找到对于的view和数据 date.index让对应view加载对应数据
package cn.new1.cloudnurse.pregnancy.main.adapter;
public class WikipediaPagerAdapter extends PagerAdapter{
//布局的view
private List<ScrollView> contentViewList = new LinkedList<ScrollView>();
private int pagerCount; //循环的个数
Context context;
public WikipediaPagerAdapter(Context context, int pagerCount) {
this.context = context;
this.pagerCount = pagerCount;// * 2;
for (int i = 0; i < pagerCount; i++) {
ScrollView scrollView = (ScrollView) View.inflate(context, R.layout.wikipedia_pager_item, null);
contentViewList.add(scrollView);
}
}
WikiPediaData date;
@Override
public void draw(int arg0, Object arg1) {
// WikiPediaData date;
try {
JSONObject jsonObject = new JSONObject((String)arg1);
date = new WikiPediaData();
date.date = jsonObject.optString("currentDate");
date.babychange = jsonObject.optString("v_baby_changes");
date.momchange = jsonObject.optString("v_mom_changes");
showView(date);
} catch (JSONException e) {
e.printStackTrace();
}
}
private void showView(final WikiPediaData date){
//获取对应数据的view然后加载数据显示
ScrollView scrollView = contentViewList.get(date.index%pagerCount);
dateTv = (TextView) scrollView.findViewById(R.id.wikipedia_date);
babyChangeTv = FindView.byId(scrollView, R.id.wikipedia_baby_change);
});
dateTv.setText(date.date);
babyChangeTv.setText(date.babychange);
}
@Override
public int getCount() {
return PregnancyParam.GESTATIONAL_DAY_COUNT; //无数个确保viewpager的数量可以一直累计
}
@Override
public boolean isViewFromObject(View view, Object obj) {
return view == obj;
}
private TextView dateTv; //日期
private TextView babyChangeTv; //宝贝变化
public static int indexCurrent = 0;
@Override
public Object instantiateItem(View view, int index) {
//要初始化的view
ViewGroup parent = (ViewGroup) contentViewList.get(index%pagerCount).getParent();
WikiPediaDb db = new WikiPediaDb(context);
WikiPediaData tmpData = db.getContactList(index+"");
if (parent != null) { //循环队列加载 部分内存会相同 最好确保不能相邻 viewpager内存实时缓存3个界面
} else {
((ViewPager) view).addView(contentViewList.get(index%pagerCount),0);
}
indexCurrent = index%pagerCount;
return contentViewList.get(index%pagerCount);
}
@Override
public void destroyItem(View view, int index, Object obj) {
((ViewPager) view).removeView(contentViewList.get(index%pagerCount)); //移除view
}
@Override
public int getItemPosition(Object object) {
// TODO Auto-generated method stub
return POSITION_UNCHANGED;
}
}
综合多页面数据变化大的推荐使用FragmentStatePagerAdapter