即使我设置oViewPager.setOffsetscreenPageLimit(0),我的视图寻呼机仍然在可见页面的每侧加载1个屏幕外页面。
如何使其仅在用户滑动到页面时加载页面
如果有帮助,我的适配器:
public class MainPagerAdapter extends FragmentPagerAdapter {
protected static final String[] CONTENT = new String[] { "page 1", "page 2", "page 3", "page 4", };
private int mCount = CONTENT.length;
public MainPagerAdapter(FragmentManager fm) {
super(fm);
}
@Override
public Fragment getItem(int position) {
//return TestFragment.newInstance(CONTENT[position % CONTENT.length]);
return MainFragment.newInstance(position);
}
@Override
public int getCount() {
return mCount;
}
@Override
public CharSequence getPageTitle(int position) {
return MainPagerAdapter.CONTENT[position % CONTENT.length];
}
public void setCount(int count) {
if (count > 0 && count <= 10) {
mCount = count;
notifyDataSetChanged();
}
}
}
另一种选择是使用OnPageChangeListener
,每当发生页面更改时,在片段中调用刷新方法。
这将要求您设置更高的OffScreenPageLimit
,但每次看到片段时都会更新。
pager.setOnPageChangeListener(new OnPageChangeListener() {
@Override
public void onPageSelected(int position){
((MyRefreshableFragment)pager.getAdapter().getItem(position)).refresh();
}
@Override
public void onPageScrolled(int arg0, float arg1, int arg2) {}
@Override
public void onPageScrollStateChanged(int arg0) {}
});
如何让它只在用户滑动到页面时加载页面?
编写自己的ViewPager
。正如Jani的回答所指出的,ViewPager
的屏幕外页面每侧的最小限制为1。
这是滑动动画顺利工作所必需的。否则,如果我们必须等待您为下一页设置UI,无论您需要多长时间才能建立UI,用户的滑动都将被冻结,或者滑动到空白内容。
你不能这么做。您将得到如下错误:"请求的屏幕外页面限制0太小;默认为1"。但在这里你可以找到更多关于它的信息:ViewPager.setOffsetscreenPageLimit(0)没有';t按预期工作
我使用Loader并初始化onPageSelected
中每个片段的Loader。
在片段中添加此方法
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
// load data here resumePlayer();
}else{
// fragment is no longer visible pausePlayer();
}
}
有源代码
/**
* Set the number of pages that should be retained to either side of the
* current page in the view hierarchy in an idle state. Pages beyond this
* limit will be recreated from the adapter when needed.
*
* <p>This is offered as an optimization. If you know in advance the number
* of pages you will need to support or have lazy-loading mechanisms in place
* on your pages, tweaking this setting can have benefits in perceived smoothness
* of paging animations and interaction. If you have a small number of pages (3-4)
* that you can keep active all at once, less time will be spent in layout for
* newly created view subtrees as the user pages back and forth.</p>
*
* <p>You should keep this limit low, especially if your pages have complex layouts.
* This setting defaults to 1.</p>
*
* @param limit How many pages will be kept offscreen in an idle state.
*/
public void setOffscreenPageLimit(int limit) {
if (limit < DEFAULT_OFFSCREEN_PAGES) {//DEFAULT_OFFSCREEN_PAGES = 1
Log.w(TAG, "Requested offscreen page limit " + limit + " too small; defaulting to " +
DEFAULT_OFFSCREEN_PAGES);
limit = DEFAULT_OFFSCREEN_PAGES;
}
if (limit != mOffscreenPageLimit) {
mOffscreenPageLimit = limit;
populate();
}
}
您可以通过复制视图寻呼机的源来自定义视图寻呼机,然后更改此方法
像这个
public class LazyViewPager extends ViewGroup {
private static final String TAG = "LazyViewPager";
private static final boolean DEBUG = false;
private static final boolean USE_CACHE = false;
private static final int DEFAULT_OFFSCREEN_PAGES = 0;//change default to load one page,no offset,ViewPager is 1,so cache 2 Fragment
private static final int MAX_SETTLE_DURATION = 600; // ms
我知道这是一个很晚的答案,但看在上帝的份上,你不必像别人建议的那样编写自己的寻呼机。
让我们从头开始:
viewpager的工作原理:
默认情况下,它会在内存的两侧保留一个项目,这样就不必每次都创建它。
第一个解决方案:
mViewPager.setOffscreenPageLimit(0);
结果是:
请求的屏幕外页面限制0太小;默认为1
第二个解决方案:
您希望在用户实际可见时更新片段,因此请使用以下方法:
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (isVisibleToUser) {
//Do something like
//adapter.notifyDataSetChanged();
}
}
希望它能在未来帮助到别人!!!
经过几轮工作,我找到了解决方案。这是完美的工作。每个选项卡片段类都实现了这些代码步骤。
private boolean loadData = false;
@Override
public void setUserVisibleHint(boolean isVisibleToUser) {
super.setUserVisibleHint(isVisibleToUser);
if (this.isVisible() && isVisibleToUser ) {
loadData = true;
// Load your data or call web services
performDataRequestAsyncTask();
}
}
和In-onCreateView加载相同的数据或调用相同的web服务,如下面的
if(!loadData && YourMainFragment.yourMainFragment.getCurrentTab() == CURRENT_TAB_INDEX){
// Load your data or call web services
performDataRequestAsyncTask();
}
在初始化视图页面的YourMainFragment中,添加此方法以获取currentTab
public int getCurrentTab(){
if(mViewPager != null) return mViewPager.getCurrentItem();
else return -1;
}