Android入门笔记 - 网络通信 - WebKit

今天来接触一下android中自带的浏览器控件 WebView。

先上一张效果图：

    
 

分为上中下三个部分，上面是EditText和Button，中间区域是WebView,下面是一个进度条显示网页加载进度。

1. layout/ activity_main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"    xmlns:tools="http://schemas.android.com/tools"    android:layout_width="match_parent"    android:layout_height="match_parent"    android:orientation="vertical"    tools:context=".MainActivity" >    <LinearLayout        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_gravity="center"        android:layout_weight="0"        android:orientation="horizontal" >        <EditText            android:id="@+id/et_address"            android:layout_width="0dp"            android:layout_height="wrap_content"            android:layout_weight="1"            android:hint="url"            android:singleLine="true" />        <Button            android:id="@+id/btn_loadurl"            android:layout_width="wrap_content"            android:layout_height="wrap_content"            android:text="跳转" />    </LinearLayout>    <WebView        android:id="@+id/web"        android:layout_width="match_parent"        android:layout_height="0dp"        android:layout_weight="1" />    <ProgressBar        android:id="@+id/progress"        style="?android:attr/progressBarStyleHorizontal"        android:layout_width="match_parent"        android:layout_height="wrap_content"        android:layout_weight="0" /></LinearLayout>

2. MainActivity.java :

package com.example.ch8_03_webkit;import android.os.Bundle;import android.app.Activity;import android.app.AlertDialog;import android.content.Context;import android.content.DialogInterface;import android.graphics.Bitmap;import android.util.Log;import android.view.Menu;import android.view.View;import android.webkit.JsResult;import android.webkit.WebChromeClient;import android.webkit.WebView;import android.webkit.WebViewClient;import android.widget.Button;import android.widget.EditText;import android.widget.ProgressBar;import android.widget.Toast;public class MainActivity extends Activity {private static final String TAG = "MainActivity";private final Activity mActivity = this;private Context mContext = this;private Button mBtnLoadUrl;private WebView mWebView;private EditText mEtUrl;private ProgressBar mProgressBar;@Overrideprotected void onCreate(Bundle savedInstanceState) {super.onCreate(savedInstanceState);setContentView(R.layout.activity_main);mEtUrl = (EditText) findViewById(R.id.et_address);mBtnLoadUrl = (Button) findViewById(R.id.btn_loadurl);mWebView = (WebView) findViewById(R.id.web);mProgressBar = (ProgressBar) findViewById(R.id.progress);mProgressBar.setVisibility(View.GONE);initWebView(mWebView);mBtnLoadUrl.setOnClickListener(new LoadurlListener());}    class LoadurlListener implements View.OnClickListener {        @Override        public void onClick(View v) {            String url = mEtUrl.getText().toString();            if (url != null && !url.equals("")) {                if (!url.contains("http://") && !url.contains("file:///")) {                    url = "http://" + url;                }                openUrl(url);            } else {                showToast("url不能为空");            }        }    }private void initWebView(WebView webview) {mWebView.getSettings().setJavaScriptEnabled(true);mWebView.getSettings().setAllowFileAccess(true);mWebView.getSettings().setBuiltInZoomControls(true);mWebView.setWebViewClient(new WebViewClient() {public boolean shouldOverrideUrlLoading(WebView view, String url) {view.loadUrl(url);return true;}@Overridepublic void onPageFinished(WebView view, String url) {// TODO Auto-generated method stubsuper.onPageFinished(view, url);}@Overridepublic void onPageStarted(WebView view, String url, Bitmap favicon) {// TODO Auto-generated method stubsuper.onPageStarted(view, url, favicon);}});webview.setWebChromeClient(new WebChromeClient() {public void onProgressChanged(WebView view, int progress) {mProgressBar.setProgress(progress);if (progress == 100) {mProgressBar.setVisibility(View.GONE);} else {mProgressBar.setVisibility(View.VISIBLE);}}@Overridepublic void onReceivedTitle(WebView view, String title) {mActivity.setTitle(title);super.onReceivedTitle(view, title);}@Overridepublic boolean onJsAlert(WebView view, String url, String message,final JsResult result) {AlertDialog.Builder builder = new AlertDialog.Builder(mContext);builder.setTitle("提示对话框");builder.setMessage(message);builder.setPositiveButton("OK",new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog,int which) {result.confirm();}});builder.setCancelable(true);builder.create();builder.show();return true;}@Overridepublic boolean onJsConfirm(WebView view, String url,String message, final JsResult result) {AlertDialog.Builder builder = new AlertDialog.Builder(mContext);builder.setTitle("可选择对话框");builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {result.confirm();}});builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {result.cancel();}});builder.setCancelable(true);builder.create();builder.show();return true;}});}@Overridepublic void onBackPressed() {if (mWebView.canGoBack()) {mWebView.goBack();return;}super.onBackPressed();}private void openUrl(String url) {mWebView.loadUrl(url);}private void showToast(String words) {Toast.makeText(mContext, words, Toast.LENGTH_SHORT).show();}@Overridepublic boolean onCreateOptionsMenu(Menu menu) {getMenuInflater().inflate(R.menu.main, menu);return true;}}

WebView常用方法：

WebView. loadUrl( String url) ： 加载网页

WebView. canGoBack() ,  WebView.goBack()  ：判断是否可回退， 网页回退

WebView中可通过 getSetting() 方法获取到设置，可以做网页的相应设置，比如是否相应 javascript，是否可访问文件，设置是否可缩放等等：

        mWebView.getSettings().setJavaScriptEnabled(true);        mWebView.getSettings().setAllowFileAccess(true);        mWebView.getSettings().setBuiltInZoomControls(true);

WebView通过设置WebViewClient设置加载网页方式，网页加载完毕，网页开始加载时的动作：

mWebView.setWebViewClient(new WebViewClient() {public boolean shouldOverrideUrlLoading(WebView view, String url) {view.loadUrl(url);return true;}@Overridepublic void onPageFinished(WebView view, String url) {// TODO Auto-generated method stubsuper.onPageFinished(view, url);}@Overridepublic void onPageStarted(WebView view, String url, Bitmap favicon) {// TODO Auto-generated method stubsuper.onPageStarted(view, url, favicon);}});

WebView还可通过设置WebChromeClient设置更详细的细致的配置，比如加载进度，html的title，相应js等：

webview.setWebChromeClient(new WebChromeClient() {public void onProgressChanged(WebView view, int progress) {mProgressBar.setProgress(progress);if (progress == 100) {mProgressBar.setVisibility(View.GONE);} else {mProgressBar.setVisibility(View.VISIBLE);}}@Overridepublic void onReceivedTitle(WebView view, String title) {mActivity.setTitle(title);super.onReceivedTitle(view, title);}@Overridepublic boolean onJsAlert(WebView view, String url, String message,final JsResult result) {AlertDialog.Builder builder = new AlertDialog.Builder(mContext);builder.setTitle("提示对话框");builder.setMessage(message);builder.setPositiveButton("OK",new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog,int which) {result.confirm();}});builder.setCancelable(true);builder.create();builder.show();return true;}@Overridepublic boolean onJsConfirm(WebView view, String url,String message, final JsResult result) {AlertDialog.Builder builder = new AlertDialog.Builder(mContext);builder.setTitle("可选择对话框");builder.setPositiveButton("OK", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {result.confirm();}});builder.setNegativeButton("Cancel", new DialogInterface.OnClickListener() {@Overridepublic void onClick(DialogInterface dialog, int which) {result.cancel();}});builder.setCancelable(true);builder.create();builder.show();return true;}});

WebView中的方法太多，大家可以自己去查。

这里需要注意的是，打开本地html文件和服务器上的html文件方式是不一样的：

服务器：  http:// www.baidu.com

本地 :  file:/// android_asset/ test.html