Android WebView的加载超时处理

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原文链接：http://www.cnblogs.com/sepsun/archive/2012/05/06/2486583.html

文章标签：

#移动开发 #java #ui

本文介绍了一种在Android的WebView中实现超时处理的方法，通过自定义WebViewClient并使用Timer进行页面加载超时检测，以及PhoneGap中类似的超时处理策略。

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上个月公司项目需要在WebView中支持超时处理，然后就开始翻api，非常奇怪的是Google竟然没有超时的这项设置。随后又Google到处查阅有没有现成的例子，结果还是一无所获。好吧，还是自己动手写个吧，先直接上代码。

package com.test.js2java;

import java.util.Timer;
import java.util.TimerTask;

import android.app.Activity;
import android.graphics.Bitmap;
import android.os.Bundle;
import android.os.Handler;
import android.os.Message;
import android.util.Log;
import android.view.Window;
import android.webkit.WebSettings;
import android.webkit.WebView;
import android.webkit.WebViewClient;


public class TestJsActivity extends Activity {
    private long timeout = 5000;

    private WebView mWebView;

    private Handler mHandler = new Handler();

    private Timer timer;

    @Override
    public void onCreate(Bundle icicle) {
        super.onCreate(icicle);
        requestWindowFeature(Window.FEATURE_NO_TITLE);
        setContentView(R.layout.main);
        mWebView = (WebView) findViewById(R.id.webview);
        WebSettings webSettings = mWebView.getSettings();
        webSettings.setJavaScriptEnabled(true);
        webSettings.setAllowFileAccess(true);
        mWebView.setWebViewClient(new WebViewClient() {
            /*
             * 创建一个WebViewClient,重写onPageStarted和onPageFinished
             * 
             * 
             * onPageStarted中启动一个计时器,到达设置时间后利用handle发送消息给activity执行超时后的动作.
             * 
             */
            @Override
            public void onPageStarted(WebView view, String url, Bitmap favicon) {
                Log.d("testTimeout", "onPageStarted...........");
                // TODO Auto-generated method stub
                super.onPageStarted(view, url, favicon);
                timer = new Timer();
                TimerTask tt = new TimerTask() {
                    @Override
                    public void run() {
                        /*
                         * 超时后,首先判断页面加载进度,超时并且进度小于100,就执行超时后的动作
                         */
                        if (TestJsActivity.this.mWebView.getProgress() < 100) {
                            Log.d("testTimeout", "timeout...........");
                            Message msg = new Message();
                            msg.what = 1;
                            mHandler.sendMessage(msg);
                            timer.cancel();
                            timer.purge();
                        }
                    }
                };
                timer.schedule(tt, timeout, 1);
            }

            /**
             * onPageFinished指页面加载完成,完成后取消计时器
             */
            @Override
            public void onPageFinished(WebView view, String url) {
                // TODO Auto-generated method stub
                super.onPageFinished(view, url);
                Log.d("testTimeout", "onPageFinished+++++++++++++++++++++++++");
                Log.d("testTimeout", "+++++++++++++++++++++++++"
                        + TestJsActivity.this.mWebView.getProgress());
                timer.cancel();
                timer.purge();
            }
        });
        mWebView.loadUrl("http://image.baidu.com/i?ct=201326592&cl=2&nc=1&lm=-1&st=-1&tn=baiduimage&istype=2&fm=index&pv=&z=0&word=%D7%C0%C3%E6&s=0");
    }
}

其中要注意的是onPageFinished的两点，第一点，官方是这样解释的：

Notify the host application that a page has finished loading. This method is called only for main frame. When onPageFinished() is called, the rendering picture may not be updated yet. To get the notification for the new Picture, use onNewPicture(WebView, Picture).

也就是说，程序只认为DOM加载完成就完成了，正在加载的图片不在这个范围之内。

第二点是，如果在JS文件中又动态去加载另一JS，onPageFinished方法会在所有的JS全部加载完毕后才调用。

最近又在研究PhoneGap，突然发现它里面也有个超时处理。顺便贴上关键代码

public class DroidGap extends Activity implements CordovaInterface {

// Flag indicates that a loadUrl timeout occurred
    int loadUrlTimeout = 0;

// LoadUrl timeout value in msec (default of 20 sec)
    protected int loadUrlTimeoutValue = 20000;

          ...........
// Load URL on UI thread
final DroidGap me = this;


// Create a timeout timer for loadUrl
                final int currentLoadUrlTimeout = me.loadUrlTimeout;
                Runnable runnable = new Runnable() {
                    public void run() {
                        try {
                            synchronized(this) {
                                wait(me.loadUrlTimeoutValue);
                            }
                        } catch (InterruptedException e) {
                            e.printStackTrace();
                        }

                        // If timeout, then stop loading and handle error
                        if (me.loadUrlTimeout == currentLoadUrlTimeout) {
                            me.appView.stopLoading();
                            LOG.e(TAG, "DroidGap: TIMEOUT ERROR! - calling webViewClient");
                            me.webViewClient.onReceivedError(me.appView, -6, "The connection to the server was unsuccessful.", url);
                        }
                    }
                };
                Thread thread = new Thread(runnable);
                thread.start();
                me.appView.loadUrl(url);

          ...........

}