Android中WebView加载网页设置进度条

<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"  tools:context=".MainActivity"  android:orientation="vertical"  >  <RelativeLayout  android:layout_width="match_parent"  android:layout_height="40dp"  android:background="#1B9A16"      />      <ProgressBar   android:id="@+id/progressBar1"   style="?android:attr/progressBarStyleHorizontal"   android:layout_width="match_parent"   android:layout_height="3dip"   android:progressDrawable="@drawable/pg"   android:visibility="gone"     />   <WebView   android:id="@+id/webview1"   android:layout_below="@id/progressBar1"   android:layout_width="match_parent"   android:layout_height="match_parent" />  </LinearLayout> 

<layer-list xmlns:android="http://schemas.android.com/apk/res/android" >   <item android:id="@android:id/background">   <shape>    <corners android:radius="2dp" />    <gradient     android:angle="270"     android:centerColor="#E3E3E3"     android:endColor="#E6E6E6"     android:startColor="#C8C8C8" />   </shape>  </item>  <item android:id="@android:id/progress">   <clip>    <shape>     <corners android:radius="2dp" />     <gradient      android:centerColor="#4AEA2F"      android:endColor="#31CE15"      android:startColor="#5FEC46" />         </shape>   </clip>  </item>  </layer-list> 

package com.example.webview;  import android.os.Bundle; import android.app.Activity; import android.transition.Visibility; import android.view.KeyEvent; import android.view.Menu; import android.view.View; import android.view.Window; import android.webkit.WebChromeClient; import android.webkit.WebSettings; import android.webkit.WebView; import android.webkit.WebViewClient; import android.widget.ProgressBar;  public class MainActivity extends Activity {    private WebView webView;  private ProgressBar pg1;  @Override  protected void onCreate(Bundle savedInstanceState) {   super.onCreate(savedInstanceState);   requestWindowFeature(Window.FEATURE_NO_TITLE);   setContentView(R.layout.activity_main);   init();   webView.loadUrl("http://www.baidu.com");  }   private void init() {   // TODO 自动生成的方法存根   webView=(WebView) findViewById(R.id.webview1);   pg1=(ProgressBar) findViewById(R.id.progressBar1);      webView.setWebViewClient(new WebViewClient(){    //覆写shouldOverrideUrlLoading实现内部显示网页    @Override    public boolean shouldOverrideUrlLoading(WebView view, String url) {     // TODO 自动生成的方法存根     view.loadUrl(url);     return true;    }   });   WebSettings seting=webView.getSettings();   seting.setJavaScriptEnabled(true);//设置webview支持javascript脚本   webView.setWebChromeClient(new WebChromeClient(){    @Override    public void onProgressChanged(WebView view, int newProgress) {     // TODO 自动生成的方法存根          if(newProgress==100){      pg1.setVisibility(View.GONE);//加载完网页进度条消失     }     else{      pg1.setVisibility(View.VISIBLE);//开始加载网页时显示进度条      pg1.setProgress(newProgress);//设置进度值     }         }   });     }     //设置返回键动作（防止按返回键直接退出程序)  @Override  public boolean onKeyDown(int keyCode, KeyEvent event) {   // TODO 自动生成的方法存根   if(keyCode==KeyEvent.KEYCODE_BACK) {    if(webView.canGoBack()) {//当webview不是处于第一页面时，返回上一个页面     webView.goBack();     return true;    }    else {//当webview处于第一页面时,直接退出程序     System.exit(0);    }          }   return super.onKeyDown(keyCode, event);  }    }