Android WebView停止點擊返回

Question

我的webview模塊不工作。每當我嘗試從任何網頁導航，應用程序崩潰給出以下錯誤

"Unfortunately the app has stopped". 

任何人都可以請解釋是什麼原因？

public class MainActivity extends ActionBarActivity { 
WebView myWebView; 
@Override 
protected void onCreate(Bundle savedInstanceState) 
{ 
    super.onCreate(savedInstanceState); 
    setContentView(R.layout.activity_main); 
    WebView mainWebView = (WebView) findViewById(R.id.mainWebView); 

    WebSettings webSettings = mainWebView.getSettings(); 
    webSettings.setJavaScriptEnabled(true); 

    mainWebView.setWebViewClient(new MyCustomWebViewClient()); 
    mainWebView.setScrollBarStyle(View.SCROLLBARS_INSIDE_OVERLAY); 

    mainWebView.loadUrl("http://nahdaschools.com/v4/index.php/apps"); 
} 

private class MyCustomWebViewClient extends WebViewClient 
{ 
    @Override 
    public boolean shouldOverrideUrlLoading(WebView view, String url) 
    { 
     view.loadUrl(url); 
     return true; 
    } 

} 

@Override 
public void onBackPressed() { 
    if (myWebView.copyBackForwardList().getCurrentIndex() > 0) { 
     myWebView.goBack(); 
    } 
    else { 
     // Your exit alert code, or alternatively line below to finish 
     super.onBackPressed(); // finishes activity 
    } 
}} 

Answer 1

有了這個，你將可以參加你最近的活動。

 @Override 
     public void onBackPressed() { 

     super.onBackPressed(); 
      moveTaskToBack(false);// finishes activity 
     } 

}} 

Answer 2

@Override 
    public boolean onKeyDown(int keyCode, KeyEvent event) { 

    if(event.getAction() == KeyEvent.ACTION_DOWN){ 
     switch(keyCode) 
     { 
     case KeyEvent.KEYCODE_BACK: 
     if(myWebView.canGoBack()){ 
       myWebView.goBack(); 
     } 
     else{ 
      finish(); 
      } 
      return true; 
     } 

     } 
     return super.onKeyDown(keyCode, event); 
      }