如何防止重新加载 Webview 页面

Question

我创建了一个应用程序，其中有 3 个选项卡来使用片段显示网页。每次我从选项卡 1 切换到选项卡 2 然后返回选项卡 1 时，选项卡 1 都会重新加载。我搜索了 google，但我发现解决方案不起作用。到目前为止，我已经试过了：

 @Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
mWebView.saveState(outState);
}
@Override
public void onActivityCreated(Bundle savedInstanceState) {
super.onActivityCreated(savedInstanceState);
mWebView.restoreState(savedInstanceState); 
}

还有这个：

 <activity ...
      android:launchMode="singleInstance"
    android:alwaysRetainTaskState="true">

这是我的主要内容Activity

import android.annotation.TargetApi;
import android.os.Build;
import android.os.Bundle;
import android.support.v4.view.ViewPager;
import android.support.v7.app.ActionBarActivity;
import android.support.v7.widget.Toolbar;
import android.view.Menu;
import android.view.MenuItem;

import com.tech.slidechat.adaptor.SlidingTabLayout;
import com.tech.slidechat.adaptor.TabsPagerAdapter;

 @TargetApi(Build.VERSION_CODES.HONEYCOMB)
 public class MainActivity extends ActionBarActivity {
 SlidingTabLayout tabs;
 ViewPager viewPager;
 TabsPagerAdapter adapter;

 Toolbar toolbar;

CharSequence Titles[]={ "tab1", "tab2", "tab3" };
int Numboftabs =3;

@TargetApi(Build.VERSION_CODES.ICE_CREAM_SANDWICH)
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

     toolbar = (Toolbar) findViewById(R.id.tool_bar);
    setSupportActionBar(toolbar);

    adapter = new TabsPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs);
    // Assigning ViewPager View and setting the adapter
    viewPager = (ViewPager) findViewById(R.id.pager);
    viewPager.setAdapter(adapter);
    // Assiging the Sliding Tab Layout View
    tabs = (SlidingTabLayout) findViewById(R.id.tabs);
    tabs.setDistributeEvenly(true);
    tabs.setCustomTabColorizer(new SlidingTabLayout.TabColorizer() {
        @Override
        public int getIndicatorColor(int position) {
            return getResources().getColor(R.color.tabsScrollColor);
        }

        @Override
        public int getDividerColor(int i) {
            return 0;
        }
    });

    tabs.setViewPager(viewPager);
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

这是我的 Webview 片段之一：

  import android.os.Bundle;
  import android.support.v4.app.Fragment;
  import android.view.KeyEvent;
  import android.view.LayoutInflater;
  import android.view.View;
  import android.view.ViewGroup;
  import android.webkit.WebChromeClient;
  import android.webkit.WebView;
  import android.webkit.WebViewClient;
  import android.widget.ProgressBar;

  public class GamesFragment extends Fragment {

private ProgressBar progress;


@Override
public View onCreateView(LayoutInflater inflater, ViewGroup container,
                         Bundle savedInstanceState) {

    View rootView = inflater.inflate(R.layout.fragment_games, container, false);

    String url = "http://myurl.com";
    WebView myWebView  = (WebView) rootView.findViewById(R.id.webViewGames);
    myWebView.setWebChromeClient(new myWebViewClient());
    myWebView.getSettings().setJavaScriptEnabled(true);
    progress = (ProgressBar) rootView.findViewById(R.id.progressBar);
    progress.setMax(100);
    myWebView.loadUrl(url);


    myWebView.setWebViewClient(new WebViewClient() {

        @Override
        public boolean shouldOverrideUrlLoading(WebView View, String url) {
            View.loadUrl(url);
            GamesFragment.this.progress.setProgress(0);
            return true;
        }
    });


    myWebView.setOnKeyListener(new android.view.View.OnKeyListener()

    {
        @Override
        public boolean onKey(View v, int keyCode, KeyEvent event) {
            if (event.getAction() == KeyEvent.ACTION_DOWN) {
                WebView webView = (WebView) v;

                switch (keyCode) {
                    case KeyEvent.KEYCODE_BACK:
                        if (webView.canGoBack()) {
                            webView.goBack();
                            return true;
                        }
                        break;
                }
            }

            return false;
        }
    });
    return rootView;

}


private class myWebViewClient extends WebChromeClient {
    @Override
    public void onProgressChanged(WebView view, int newProgress) {
        GamesFragment.this.setValue(newProgress);
        super.onProgressChanged(view, newProgress);
    }
}

public void setValue(int progress) {
    this.progress.setProgress(progress);
}


}

一件有趣的事情是，每当我使用 Tab1 和 Tab2 时，它们都不会重新加载，但是当我切换到 Tab3 然后返回到 Tab1 时，只有它会重新加载。

任何帮助将不胜感激。

Answer 1

您可以尝试添加：

viewPager.setOffscreenPageLimit(2);

根据文档，setOffscreenPageLimit 是：

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.

...

You should keep this limit low, especially if your pages have complex >layouts. This setting defaults to 1.

默认值为 1，因此当您转到选项卡 3 时，当前选项卡左侧有两个选项卡，因此会重新创建选项卡 1。

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