我正在使用Xamarin工作室开发Android应用程序，但这并不重要。
我使用pageViewer上传片段（12或多或少）。对于一个显示片段，我使用webView显示本地html页面，并且向左滑动，webview内容将更改为下一个。
所以，即使我在我的代码中使用了不同的任务，在第五个幻想中也会出现内存问题。
我的问题是：当我没有显示片段时，有没有办法'分离'片段？他们不能留在我的记忆中吗？
全部谢谢
这是我的代码，N.B：Java答案也加入了
protected override void OnCreate (Bundle bundle)
{
base.OnCreate (bundle);
SetContentView (Resource.Layout.BookView);
_loader = ProgressDialog.Show (this, "Loading...", "Please wait...", true);
//return chapters count
chapters = 12 //example
//var dp = (int)Resources.DisplayMetrics.Density;
_layout = FindViewById<DrawerLayout> (Resource.Id.drawer_layout);
_view = FindViewById<ViewPager>(Resource.Id.bView);
_view.SetBackgroundColor (Color.White);
_currentAdapter = new AwesomeFragmentAdapter (SupportFragmentManager, path, name, chapters, this, _view);
_view.Adapter = _currentAdapter;
_view.OffscreenPageLimit = chapters;
List<int> positions = new List<int> ();
_view.PageSelected += (object sender, ViewPager.PageSelectedEventArgs e) => {
//get details
var page_load = new Task (() => {
//return an object with the chapter details
_chap = object;
});
page_load.Start();
//find the webview
_web = (WebView)_view.FindViewWithTag(300 + e.Position);
WebSettings setting = _web.Settings;
setting.CacheMode = CacheModes.Default;
setting.JavaScriptEnabled = true;
setting.BuiltInZoomControls = true;
setting.DisplayZoomControls = false;
setting.PluginsEnabled = true;
setting.SetPluginState(WebSettings.PluginState.On);
//setting.JavaScriptCanOpenWindowsAutomatically = true;
if (positions.Contains(e.Position)) {
_web.ClearCache(true);
_web.ClearView();
}
//Start when the scroll is finished
_view.PageScrollStateChanged += (object sendero, ViewPager.PageScrollStateChangedEventArgs ex) => {
if (ex.State == 0 ) {
if (positions.Contains(e.Position)) {
//_web.Reload(); --> doesn't work
//Doesn't reload the .js animations
_web.LoadUrl ("file://" + path + "/" + _chap.Name);
} else {
_web.LoadUrl ("file://" + path + "/" + _chap.Name);
positions.Add(e.Position);
}
}
};
};
}
public class BWebClient : WebViewClient
{
int _position;
string _path;
Activity _parent;
ViewPager _pager;
string _chapName;
public BWebClient (int position, string Path, Activity Parent, ViewPager Pager, string ChapName){
_position = position;
_parent = Parent;
_path = Path;
_pager = Pager;
_chapName = ChapName;
}
public override void OnPageFinished (WebView view, string url)
{
base.OnPageFinished (view, url);
view.ScrollTo (0, _position);
}
public override bool ShouldOverrideUrlLoading (WebView view, string url)
{
if (url.StartsWith ("navigate")) {
string destination = url.Substring (url.IndexOf ("navigate://") + "navigate://".Length);
int DestinationChapter = Int32.Parse (destination.Substring (0, destination.IndexOf("_")));
int l = destination.IndexOf("_") + 1;
int b = destination.Length - l;
int DestinationPage = Int32.Parse (destination.Substring (l,b));
if (DestinationPage == 0) {
_pager.SetCurrentItem(DestinationChapter ,true);
WebView _web = (WebView)_pager.FindViewWithTag(300 + DestinationChapter);
_web.LoadUrl ("file://" + _path + "/" + _chapName);
}
} else if (url.StartsWith ("pdf")) {
string file_path = System.IO.Path.Combine (_path, url.Substring (url.IndexOf ("pdf://") + "pdf://".Length));
Android.Net.Uri pdfFile = Android.Net.Uri.FromFile (new Java.IO.File (file_path));
Intent pdfIntent = new Intent (Intent.ActionView);
pdfIntent.SetDataAndType (pdfFile, "application/pdf");
_parent.StartActivity (pdfIntent);
}
return true;
}
}
public class AwesomeFragmentAdapter : FragmentPagerAdapter
{
string _path;
string _filename;
int _chapters;
Activity _parent;
FileUtilities _fUtils;
ViewPager _pager;
public AwesomeFragmentAdapter (Android.Support.V4.App.FragmentManager fm,
string path,
string filename,
int chapters,
Activity parent,
FileUtilities FUtils,
ViewPager Pagers): base(fm)
{
_path = path;
_filename = filename;
_chapters = chapters;
_parent = parent;
_fUtils = FUtils;
_pager = Pagers;
}
public override int Count
{
/* --- return chapter count --- */
get { return _chapters;}
}
public override Android.Support.V4.App.Fragment GetItem(int _position)
{
/* --- get specific item --- */
return new AwesomeFragment (_path, _filename, _position, _parent, _fUtils, _pager);
}
}
public class AwesomeFragment : Android.Support.V4.App.Fragment
{
string _path;
WebView web_view;
string _filename;
int _position;
Activity _parent;
BanjiChapter _chap;
FileUtilities _fUtils;
ViewPager _pager;
public AwesomeFragment () {}
public AwesomeFragment (string path,
string filename,
int position,
Activity parent,
FileUtilities FUtils,
ViewPager Pager)
{
_path = path;
_filename = filename;
_position = position;
_parent = parent;
_fUtils = FUtils;
_pager = Pager;
}
public override View OnCreateView (LayoutInflater inflater, ViewGroup container, Bundle savedInstanceState)
{
/* --- Create the view --- */
var view = inflater.Inflate (Resource.Layout.BookWebView, container, false);
//return the chapter
_chap = _fUtils.ReturnChapterDetails(_filename, _position);
web_view = view.FindViewById<WebView> (Resource.Id.webview);
web_view.SetWebViewClient(new BanjiWebClient(_position,_path,_parent, _pager, _chap.Name ));
web_view.SetBackgroundColor(Color.Transparent);
web_view.Settings.JavaScriptEnabled = true;
web_view.Tag = 300 + _position;
switch(Resources.DisplayMetrics.DensityDpi){
case Android.Util.DisplayMetricsDensity.Medium:
{
web_view.SetLayerType (LayerType.Software, null);
break;
}
case Android.Util.DisplayMetricsDensity.High:
{
web_view.SetLayerType (LayerType.Hardware, null);
break;
}
case Android.Util.DisplayMetricsDensity.Xhigh:
{
web_view.SetLayerType (LayerType.Hardware, null);
break;
}
}
if (_chap.Background == null) {
view.SetBackgroundColor (Color.White);
} else {
view.SetBackgroundDrawable (new BitmapDrawable (BitmapFactory.DecodeByteArray (_chap.Background, 0, _chap.Background.Length)));
}
if (_position == 0) {
web_view.LoadUrl ("file://" + _path + "/" + _chap.Name);
}
return view;
}
public BChapter GetCurrentBChapter()
{
return _chap;
}
}
编辑：
BookView.axml
<?xml version="1.0" encoding="utf-8"?>
<android.support.v4.widget.DrawerLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/drawer_layout"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:background="#ffececec">
<!-- The main content view -->
<FrameLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/mainView">
<android.support.v4.view.ViewPager
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/bookView" />
<ImageButton
android:layout_height="wrap_content"
android:layout_width="wrap_content"
android:layout_gravity="left|center"
android:background="@null"
android:id="@+id/menuButton"
/>
</FrameLayout>
<!-- The navigation drawer -->
<LinearLayout
android:id="@+id/left_menu"
android:layout_width="250dp"
android:layout_height="match_parent"
android:choiceMode="singleChoice"
android:layout_gravity="start"
android:divider="@android:color/transparent"
android:dividerHeight="0dp"
android:background="#111">
<Button
android:id="@+id/backStep"
android:layout_width="fill_parent"
android:layout_height="wrap_content"
style="@style/button_text"
android:background="#ff000000"
android:fitsSystemWindows="false" />
<Space
android:layout_width="fill_parent"
android:layout_height="wrap_content" />
<ScrollView
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/screllArea">
<LinearLayout
android:layout_width="match_parent"
android:layout_height="match_parent"
android:id="@+id/ThumbLayout" />
</ScrollView>
</LinearLayout>
</android.support.v4.widget.DrawerLayout>
BookWebView
<?xml version="1.0" encoding="utf-8"?>
<WebView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="@+id/webview"
android:layout_width="match_parent"
android:layout_height="match_parent" />
答案 0 :(得分：1)
使用FragmentStatePagerAdapter代替;它旨在通过在片段不可见时销毁片段来最小化内存开销，仅保存片段的状态信息。
来自开发者文档：
This version of the pager is more useful when there are a large number of pages, working more like a list view. When pages are not visible to the user, their entire fragment may be destroyed, only keeping the saved state of that fragment. This allows the pager to hold on to much less memory associated with each visited page as compared to FragmentPagerAdapter at the cost of potentially more overhead when switching between pages.