在Webview中加载ProgresBar

Question

我有问题。 我在main2activity中做一个progressbar。 应用程序启动，但其网站载入进度栏时不会消失。 而我的应用程序崩溃。 请帮忙！ ：* 我想更正我的代码，因为这是了解错误发生的最佳方法。 谢谢！

有代码：

package musial.pzstis.com.pzstiz; 

import android.app.Activity; 
import android.graphics.Bitmap; 
import android.os.Bundle; 
import android.view.KeyEvent; 
import android.view.View; 
import android.webkit.WebSettings; 
import android.webkit.WebView; 
import android.webkit.WebViewClient; 
import android.widget.ProgressBar; 

/* 
* Demo of creating an application to open any URL inside the application and clicking on any link from that URl 
should not open Native browser but that URL should open in the same screen. 

- Load WebView with progress bar 
*/ 
public class Main2Activity extends Activity { 
    /** Called when the activity is first created. */ 

    WebView myWebView; 
    ProgressBar progressBar; 

    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.activity_main2); 

     myWebView = (WebView) findViewById(R.id.webView); 
     progressBar = (ProgressBar) findViewById(R.id.progressBar7); 

     myWebView.setWebViewClient(new myWebClient()); 
     myWebView.getSettings().setJavaScriptEnabled(true); 
     WebSettings webSettings = myWebView.getSettings(); 
     myWebView.loadUrl("https://docs.google.com/viewer?url=http%3A%2F%2Fpzstiz.swiebodzin.pl%2Fzastepstwa%2FPZSTiZ_zastepstwa.pdf"); 
     webSettings.setBuiltInZoomControls(true); 
     webSettings.setSupportZoom(true); 
     myWebView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE); 
     myWebView.getSettings().setRenderPriority(WebSettings.RenderPriority.HIGH); 

    } 

    public class myWebClient extends WebViewClient 
    { 
     @Override 
     public void onPageStarted(WebView view, String url, Bitmap favicon) { 
      // TODO Auto-generated method stub 
      super.onPageStarted(view, url, favicon); 
     } 

     @Override 
     public boolean shouldOverrideUrlLoading(WebView view, String url) { 
      // TODO Auto-generated method stub 
      progressBar.setVisibility(View.VISIBLE); 
      view.loadUrl(url); 
      return true; 

     } 

     @Override 
     public void onPageFinished(WebView view, String url) { 
      // TODO Auto-generated method stub 
      super.onPageFinished(view, url); 

      progressBar.setVisibility(View.GONE); 
     } 
    } 

    // To handle "Back" key press event for WebView to go back to previous screen. 
    @Override 
    public boolean onKeyDown(int keyCode, KeyEvent event) 
    { 
     if ((keyCode == KeyEvent.KEYCODE_BACK) && myWebView.canGoBack()) { 
      myWebView.goBack(); 
      return true; 
     } 
     return super.onKeyDown(keyCode, event); 
    } 
} 

有日志：

02-14 20:43:38.592 20262-20299/musial.pzstis.com.pzstiz E/EGL_emulation: tid 20299: eglSurfaceAttrib(1174): error 0x3009 (EGL_BAD_MATCH) 
02-14 20:43:44.672 20262-20262/musial.pzstis.com.pzstiz E/AndroidRuntime: FATAL EXCEPTION: main 
                      Process: musial.pzstis.com.pzstiz, PID: 20262 
                      java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.ProgressBar.setVisibility(int)' on a null object reference 
                       at musial.pzstis.com.pzstiz.Main2Activity$myWebClient.onPageFinished(Main2Activity.java:66) 
                       at com.android.webview.chromium.WebViewContentsClientAdapter.onPageFinished(WebViewContentsClientAdapter.java:531) 
                       at org.chromium.android_webview.AwContentsClientCallbackHelper$MyHandler.handleMessage(AwContentsClientCallbackHelper.java:188) 
                       at android.os.Handler.dispatchMessage(Handler.java:102) 
                       at android.os.Looper.loop(Looper.java:154) 
                       at android.app.ActivityThread.main(ActivityThread.java:6119) 
                       at java.lang.reflect.Method.invoke(Native Method) 
                       at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:886) 
                       at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:776) 
02-14 20:43:44.777 1569-4538/system_process E/EGL_emulation: tid 4538: eglSurfaceAttrib(1174): error 0x3009 (EGL_BAD_MATCH) 

Answer 1

那么，你得到了与进度的空指针异常，我将封装每次访问这种形式的进度：

if(progressBar == null) 
    progressBar = (ProgressBar) findViewById(R.id.progressBar7); 
if(progressBar) 
    progressBar.setVisibility(View.GONE); 

实现在vour代码：

public class Main2Activity extends Activity { 
/** Called when the activity is first created. */ 

WebView myWebView; 
ProgressBar progressBar; 

@Override 
public void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main2); 

    myWebView = (WebView) findViewById(R.id.webView); 
    progressBar = (ProgressBar) findViewById(R.id.progressBar7); 

    myWebView.setWebViewClient(new myWebClient(this)); 
    myWebView.getSettings().setJavaScriptEnabled(true); 
    WebSettings webSettings = myWebView.getSettings(); 
    myWebView.loadUrl("https://docs.google.com/viewer?url=http%3A%2F%2Fpzstiz.swiebodzin.pl%2Fzastepstwa%2FPZSTiZ_zastepstwa.pdf"); 
    webSettings.setBuiltInZoomControls(true); 
    webSettings.setSupportZoom(true); 
    myWebView.getSettings().setCacheMode(WebSettings.LOAD_NO_CACHE); 
    myWebView.getSettings().setRenderPriority(WebSettings.RenderPriority.HIGH); 

} 

public class myWebClient extends WebViewClient 
{ 

    privat Activity main2ac; 
    ProgressBar progressBar; 

    public myWebClient(Activity handle){ 
     main2ac = handle; 
    } 

    @Override 
    public void onPageStarted(WebView view, String url, Bitmap favicon) { 
     // TODO Auto-generated method stub 
     super.onPageStarted(view, url, favicon); 
    } 

    @Override 
    public boolean shouldOverrideUrlLoading(WebView view, String url) { 
    // TODO Auto-generated method stub 

     if(progressBar == null) 
      progressBar = (ProgressBar)main2ac.findViewById(R.id.progressBar7); 
     if(progressBar) 
      progressBar.setVisibility(View.VISIBLE); 
     view.loadUrl(url); 
     return true; 
    } 

    @Override 
    public void onPageFinished(WebView view, String url) { 
     // TODO Auto-generated method stub 
     super.onPageFinished(view, url); 

     if(progressBar == null) 
      progressBar = (ProgressBar)main2ac.findViewById(R.id.progressBar7); 
     if(progressBar) 
      progressBar.setVisibility(View.GONE); 
    } 
} 

Answer 2

通行证进度您的自定义网页视图：

myWebView.setWebViewClient(new myWebClient(progressBar)); 

更改myWebClient类这样的：

public class myWebClient extends WebViewClient { 
    private ProgressBar progressBar; 

    public myWebClient(ProgressBar progressBar) { 
     this.progressBar=progressBar; 
     progressBar.setVisibility(View.VISIBLE); 
    } 
    @Override 
    public boolean shouldOverrideUrlLoading(WebView view, String url) { 
     // TODO Auto-generated method stub 
     view.loadUrl(url); 
     return true; 
    } 

    @Override 
    public void onPageFinished(WebView view, String url) { 
     // TODO Auto-generated method stub 
     super.onPageFinished(view, url); 
     progressBar.setVisibility(View.GONE); 
    } 
} 

希望这有助于。