Android WebView最佳优化（WebView池）

前言

说到优化是个老生常谈的话题了，如内存泄露这种，只要遵循一定的编码规则，大部分能避免。本文说下WebView优化，如何大幅提高WebView加载网页速度。

WebView优化方法总结如下：

• WebView 动态加载和销毁
• 独立的web进程，与主进程隔开，解决任何webview内存泄漏之类的问题
• 实现WebView复用
• DNS解析优化（接口与网页主域名一致）
• 离线预推，下发离线包，并增量更新
• 网页按节点局部刷新
• 自定义实现图片资源缓存
• 加载本地网页

本文主要说明如何实现WebView复用（WebView池），基于X5 WebView优化。X5与原生的WebView相比，本身已经做了很多加载优化，如果加上WebView池，加载效果更加明显，给人丝滑般流畅。网上的WebView池方案基本没有考虑视图缓存问题，即复用WebView时，加载新页面，存在历史浏览页面问题。

优化
国际规则，贴上核心代码：

WebViewPool：

package com.sjl.bookmark.util;

import android.view.ViewGroup;

import com.sjl.bookmark.app.MyApplication;
import com.sjl.bookmark.widget.X5WebView;

import java.util.ArrayList;
import java.util.List;


public class WebViewPool {
    private static List<WebVieWrap> webViewPool = new ArrayList<>();

    private static int maxSize = 2;


    private WebViewPool() {
        webViewPool = new ArrayList<>();

    }

    private static volatile WebViewPool instance = null;

    public static WebViewPool getInstance() {
        if (instance == null) {
            synchronized (WebViewPool.class) {
                if (instance == null) {
                    instance = new WebViewPool();
                }
            }
        }
        return instance;
    }

    /**
     * webView 初始化
     * 最好放在application onCreate里
     */
    public static void init() {
        for (int i = 0; i < maxSize; i++) {
            X5WebView webView = new X5WebView(MyApplication.getContext());
            WebVieWrap webVieWrap = new WebVieWrap();
            webVieWrap.x5WebView = webView;
            webViewPool.add(webVieWrap);
        }
    }


    /**
     * 获取webView
     */
    public synchronized X5WebView getWebView() {
        if (webViewPool.size() < maxSize) {
            return buildWebView();
        }
        X5WebView x5WebView = checkWebView();
        if (x5WebView != null) {
            return x5WebView;
        }
        //再次判断
        if (webViewPool.size() < maxSize) {
            return buildWebView();
        }
        try {
            wait(2 * 1000);
            x5WebView = getWebView();
            return x5WebView;
        } catch (Exception e) {
        }
        throw new RuntimeException("webView池已满");
    }


    private  X5WebView checkWebView() {
        for (int i = webViewPool.size() - 1; i >= 0; i--) {
            WebVieWrap webVieWrap = webViewPool.get(i);
            if (webVieWrap.inUse) {
                continue;
            }
            X5WebView x5WebView = webVieWrap.x5WebView;
            webVieWrap.inUse = true;
            return x5WebView;
        }
        return null;
    }


    /**
     * 回收webView
     * @param webView
     */
    public synchronized void recycleWebView(X5WebView webView) {
        for (int i = 0; i < webViewPool.size(); i++) {
            WebVieWrap webVieWrap = webViewPool.get(i);
            X5WebView temp = webVieWrap.x5WebView;
            if (webView == temp) {
                temp.stopLoading();
                temp.setWebChromeClient(null);
                temp.setWebViewClient(null);
                temp.clearHistory();
//                temp.clearCache(true);
                temp.loadUrl("about:blank");
                temp.pauseTimers();
                webVieWrap.inUse = false;
                break;
            }
        }
        notifyAll();
    }

    /**
     * 创建webView
     * @return
     */
    private X5WebView buildWebView() {
        X5WebView webView = new X5WebView(MyApplication.getContext());
        WebVieWrap webVieWrap = new WebVieWrap();
        webVieWrap.x5WebView = webView;
        webViewPool.add(webVieWrap);
        return webView;
    }


    /**
     * 销毁连接池
     */
    public static void destroyPool() {
        try {
            if (webViewPool.size() == 0) {
                return;
            }
            for (WebVieWrap webVieWrap : webViewPool) {
                X5WebView webView = webVieWrap.x5WebView;
                webView.destroy();
            }
            webViewPool.clear();
        } catch (Exception e) {
            e.printStackTrace();
        }

    }


    /**
     * 回收webView ,解绑
     *
     * @param webView 需要被回收的webView
     */
    public void recycleWebView(ViewGroup view, X5WebView webView) {
        if (view != null && webView != null){
            recycleWebView(webView);
            view.removeView(webView);

        }
    }

    /**
     * 设置webView池个数
     *
     * @param size webView池个数
     */
    public void setMaxPoolSize(int size) {
        maxSize = size;
    }

    public static class WebVieWrap {
        public X5WebView x5WebView;
        public boolean inUse;

    }
}

X5WebView:

public class X5WebView extends WebView {

  
    public X5WebView(Context arg0) {
        this(arg0,null);
    }


    public X5WebView(Context arg0, AttributeSet arg1) {
        super(arg0, arg1);
        setBackgroundColor(85621);
        if (!isInEditMode()) {
            initView(arg0);
        }
        initWebViewSettings();
        this.getView().setClickable(true);
        this.getView().setOverScrollMode(View.OVER_SCROLL_ALWAYS);

    }

    private void initView(Context context) {

        LogUtils.i(getX5WebViewExtension() == null ? "Sys Core" : "X5  Core:" + QbSdk.getTbsVersion(getContext()));

    }

    private void initWebViewSettings() {
        WebSettings webSettings = this.getSettings();
        webSettings.setAllowFileAccess(true);
        webSettings.setLayoutAlgorithm(LayoutAlgorithm.NARROW_COLUMNS);
        webSettings.setSupportZoom(true);
        webSettings.setBuiltInZoomControls(true);
        webSettings.setDisplayZoomControls(false); //隐藏原生的缩放控件
        webSettings.setUseWideViewPort(true);
        webSettings.setSupportMultipleWindows(false);
        webSettings.setLoadWithOverviewMode(true);
        webSettings.setAppCacheEnabled(true);
        webSettings.setDatabaseEnabled(true);
        webSettings.setDomStorageEnabled(true);
        webSettings.setJavaScriptEnabled(true);
        webSettings.setGeolocationEnabled(true);
        webSettings.setAppCacheMaxSize(Long.MAX_VALUE);
        webSettings.setAppCachePath(this.getContext().getDir("appcache", 0).getPath());
        webSettings.setDatabasePath(this.getContext().getDir("databases", 0).getPath());
        webSettings.setGeolocationDatabasePath(this.getContext().getDir("geolocation", 0)
                .getPath());
        webSettings.setPluginState(WebSettings.PluginState.ON_DEMAND);
        //this.getSettingsExtension().setPageCacheCapacity(IX5WebSettings.DEFAULT_CACHE_CAPACITY);//extension// settings 的设计
    }

  
}

Activity或Fragment使用伪代码：

  private boolean clear;
  
 @Override
    protected void onCreate(@Nullable Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
      	//mViewParent 为 FrameLayout，动态添加WebView到FrameLayout中
	   mWebView = WebViewPool.getInstance().getWebView();
	   mViewParent.addView(mWebView, new FrameLayout.LayoutParams(
	                FrameLayout.LayoutParams.MATCH_PARENT,
	                FrameLayout.LayoutParams.MATCH_PARENT));
	    mWebView.setWebViewClient(new WebViewClient() {
        
            @Override
            public void doUpdateVisitedHistory(WebView webView, String s, boolean b) {
            	//处理历史视图问题
                if (clear){
                    webView.clearHistory();
                    clear = false;
                }
            }
        });
    }
   
        

  @Override
    protected void onDestroy() {
        super.onDestroy();
        WebViewPool.getInstance().recycleWebView(mViewParent,mWebView);
        mWebView = null;
       /* if (mWebView != null) {
            mWebView.release();
        }*/
    }

关于X5 教程参考：https://x5.tencent.com/docs/access.html