android的WebView、WebViewClient、WebChromeClient的关系

在WebView的设计中，不是什么事都要WebView类干的，有些杂事是分给其他人的，这样WebView专心干好自己的解析、渲染工作就行了。WebViewClient就是帮助WebView处理各种通知、请求事件的，具体来说包括：

onLoadResource、onPageStart、onPageFinish、onReceiveError、onReceivedHttpAuthRequest；

WebChromeClient是辅助WebView处理Javascript的对话框，网站图标，网站title，加载进度等

onCloseWindow(关闭WebView)、onCreateWindow()、onJsAlert (WebView上alert是弹不出来东西的，需要定制你的WebChromeClient处理弹出)、onJsPrompt、onJsConfirm、onProgressChanged、onReceivedIcon、onReceivedTitle；

下面看看这三者之间的应用关系；

package EOE.android.demo1;
import java.io.FileOutputStream;
import android.app.Activity;
import android.app.AlertDialog;
import android.app.AlertDialog.Builder;
import android.content.DialogInterface;
import android.graphics.Bitmap;
import android.graphics.Canvas;
import android.graphics.Picture;
import android.os.Bundle;
import android.view.KeyEvent;
import android.view.View;
import android.webkit.JsPromptResult;
import android.webkit.JsResult;
import android.webkit.WebChromeClient;
import android.webkit.WebViewClient;
import android.widget.Button;
import android.widget.Toast;

public class MainWebView3 extends Activity {

/** Called when the activity is first created. */

@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);

// 定义UI组件
Button b1 = (Button) findViewById(R.id.Button01);
Button b2 = (Button) findViewById(R.id.Button02);
Button b3 = (Button) findViewById(R.id.Button03);
final WebView wv = (WebView) findViewById(R.id.WebView01);

// 覆盖默认后退按钮的作用，替换成WebView里的查看历史页面
wv.setOnKeyListener(new View.OnKeyListener() {
@Override
public boolean onKey(View v, int keyCode, KeyEvent event) {
if (event.getAction() == KeyEvent.ACTION_DOWN) {
if ((keyCode == KeyEvent.KEYCODE_BACK) && wv.canGoBack()) {
wv.goBack();
return true;
}
}
return false;
}

});

// 设置支持Javascript

wv.getSettings().setJavaScriptEnabled(true);

// 定义并绑定按钮单击监听器

b1.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {

// 加载URL assets目录下的内容可以用 "[url=file:///android_asset]file:///android_asset[/url]" 前缀

wv.loadUrl("[url=file:///android_asset/html/test1.html]file:///android_asset/html/test1.html[/url]");

}

});

// 定义并绑定按钮单击监听器

b2.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {

// 加载URL assets目录下的内容可以用 "[url=file:///android_asset]file:///android_asset[/url]" 前缀

wv.loadUrl("[url=file:///android_asset/html/test3.html]file:///android_asset/html/test3.html[/url]");

}

});

// 定义并绑定按钮单击监听器

b3.setOnClickListener(new View.OnClickListener() {

@Override
public void onClick(View v) {

Picture pic = wv.capturePicture();

int width = pic.getWidth();

int height = pic.getHeight();

if (width > 0 && height > 0) {

Bitmap bmp = Bitmap.createBitmap(width, height, Bitmap.Config.ARGB_8888);

Canvas canvas = new Canvas(bmp);

pic.draw(canvas);

try {

String fileName = "sdcard/" + System.currentTimeMillis() + ".png";

FileOutputStream fos = new FileOutputStream(fileName);

if (fos != null) {

bmp.compress(Bitmap.CompressFormat.PNG, 90, fos);

fos.close();

}

Toast.makeText(getApplicationContext(), "截图成功，文件名是：" + fileName, Toast.LENGTH_SHORT).show();

} catch (Exception e) {

e.printStackTrace();

}

}

}

});

// 创建WebViewClient对象

WebViewClient wvc = new WebViewClient() {

@Override
public boolean shouldOverrideUrlLoading(WebView view, String url) {

Toast.makeText(getApplicationContext(), "WebViewClient.shouldOverrideUrlLoading", Toast.LENGTH_SHORT) .show();

// 使用自己的WebView组件来响应Url加载事件，而不是使用默认浏览器器加载页面

wv.loadUrl(url);

// 记得消耗掉这个事件。给不知道的朋友再解释一下，Android中返回True的意思就是到此为止吧,事件就会不会冒泡传递了，我们称之为消耗掉

return true;

}

@Override
public void onPageStarted(WebView view, String url, Bitmap favicon) {

Toast.makeText(getApplicationContext(), "WebViewClient.onPageStarted", Toast.LENGTH_SHORT).show();

super.onPageStarted(view, url, favicon);

}

@Override
public void onPageFinished(WebView view, String url) {
Toast.makeText(getApplicationContext(), "WebViewClient.onPageFinished", Toast.LENGTH_SHORT).show();

super.onPageFinished(view, url);

}

@Override
public void onLoadResource(WebView view, String url) {

Toast.makeText(getApplicationContext(), "WebViewClient.onLoadResource", Toast.LENGTH_SHORT).show();

super.onLoadResource(view, url);

}

};

// 设置WebViewClient对象

wv.setWebViewClient(wvc);

// 创建WebViewChromeClient

WebChromeClient wvcc = new WebChromeClient() {

// 处理Alert事件

@Override
public boolean onJsAlert(WebView view, String url, String message, final JsResult result) {

// 构建一个Builder来显示网页中的alert对话框

Builder builder = new Builder(MainWebView3.this);

builder.setTitle("计算1+2的值");

builder.setMessage(message);

builder.setPositiveButton(android.R.string.ok, new AlertDialog.OnClickListener() {

@Override
public void onClick(DialogInterface dialog, int which) {

result.confirm();

}

});

builder.setCancelable(false);

builder.create();

builder.show();

return true;

}

@Override
public void onReceivedTitle(WebView view, String title) {

MainWebView3.this.setTitle("可以用onReceivedTitle()方法修改网页标题");

super.onReceivedTitle(view, title);

}

// 处理Confirm事件

@Override
public boolean onJsConfirm(WebView view, String url, String message, final JsResult result) {

Builder builder = new Builder(MainWebView3.this);

builder.setTitle("删除确认");

builder.setMessage(message);

builder.setPositiveButton(android.R.string.ok, new AlertDialog.OnClickListener() {

@Override
public void onClick(DialogInterface dialog, int which) {

result.confirm();

}

});

builder.setNeutralButton(android.R.string.cancel, new AlertDialog.OnClickListener() {

@Override
public void onClick(DialogInterface dialog, int which) {

result.cancel();

}

});

builder.setCancelable(false);

builder.create();

builder.show();

return true;

}

// 处理提示事件

@Override
public boolean onJsPrompt(WebView view, String url, String message, String defaultValue,

JsPromptResult result) {

// 看看默认的效果

return super.onJsPrompt(view, url, message, defaultValue, result);

}

};

// 设置setWebChromeClient对象

wv.setWebChromeClient(wvcc);

}

}

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