java - 自定义对话框执行 NPE

Question

我将警报和对话框放在单独的类中以防止困惑。在我的 Activity 中，我有一个 webView，HTML 文档有一个在 Android 中执行自定义对话框的按钮。我使用 JavaScriptInterface 在 HTML 文档中的 JavaScript 函数和 Android Java 方法之间进行通信。除了这个自定义对话框之外，这一切都可以很好地处理我的 toast 消息和彼此之间的其他功能。

更新:

我做了一些改变，现在至少我得到了一个我无法遵循的 NPE。我将 Dialog 方法移至 JavaInterface，以使其更易于调试和其他一些更改；请参阅代码中的注释。

我不知道我做错了什么。我在 LogCat 中没有收到此错误信息；只是强制关闭应用程序...？请查看下面我的代码。

感谢您的帮助!!

日志猫:

Miss a drag as we are waiting for WebCore's response for touch down. threadid=9: thread exiting with uncaught exception (group=0x4024ee20) FATAL EXCEPTION: WebViewCoreThread java.lang.NullPointerException
at android.app.Activity.findViewById(Activity.java:1745) at com.andaero.JavaScriptInterface.onCreateDialog(JavaScriptInterface.java:45) at android.app.Activity.onCreateDialog(Activity.java:2758) at android.app.Activity.createDialog(Activity.java:936) at android.app.Activity.showDialog(Activity.java:2851) at android.app.Activity.showDialog(Activity.java:2810) at com.andaero.JavaScriptInterface.showDashBoard(JavaScriptInterface.java:32) at android.webkit.WebViewCore.nativeTouchUp(Native Method) at android.webkit.WebViewCore.nativeTouchUp(Native Method) at android.webkit.WebViewCore.access$3600(WebViewCore.java:52) at android.webkit.WebViewCore$EventHub$1.handleMessage(WebViewCore.java:1340) at android.os.Handler.dispatchMessage(Handler.java:99) at android.os.Looper.loop(Looper.java:132) at android.webkit.WebViewCore$WebCoreThread.run(WebViewCore.java:723)
at java.lang.Thread.run(Thread.java:1020)

警报和对话框类:

public class AlertsAndDialogs extends Activity
{

    public final int CATEGORY_ID = 0;

   . . . 
  //Moved to the JavaScriptInterface Class ----->
   /* protected Dialog onCreateDialog(int id)
      {
      Dialog dialog;
      switch (id)
      {
        case CATEGORY_ID:

        AlertDialog.Builder builder;
        Context mContext = this;
        LayoutInflater inflater = (LayoutInflater) mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
        View layout = inflater.inflate(R.layout.dashboard_dialog, (ViewGroup) findViewById(R.id.webView));

        builder = new AlertDialog.Builder(mContext);
        builder.setView(layout);
        dialog = builder.create();
        break;

        default:
        dialog = null;
      }
      return dialog;
      }*/

}  

JavaScriptInterface 类:

public class JavaScriptInterface extends AlertsAndDialogs
{
    public final int CATEGORY_ID = 0;
    Context mContext;

    /** Instantiate the interface and set the context */
    JavaScriptInterface(Context c)
    {
    mContext = c;
    }

    . . .

     /** Show the DashBoard from the web page */
    public void showDashBoard()
    {
    showDialog(CATEGORY_ID);
    }

    protected Dialog onCreateDialog(int id)
    {
    Dialog dialog;
    switch (id)
    {
        case CATEGORY_ID:

        AlertDialog.Builder builder;
        //Context mContext = this;
        LayoutInflater inflater = (LayoutInflater)     mContext.getSystemService(LAYOUT_INFLATER_SERVICE);
        View layout = inflater.inflate(R.layout.dashboard_dialog, (ViewGroup) findViewById(R.id.layout_root));

        builder = new AlertDialog.Builder(mContext);
        builder.setView(layout);
        dialog = builder.create();
        break;

        default:
        dialog = null;
    }
    return dialog;
    }
    . . . 
}

在包含 WebView 的主 Activity 中:

. . .
myWebView.addJavascriptInterface(new JavaScriptInterface(this), "Android");
. . .

HTML 函数:

<script type="text/javascript">
    function showDashBoardFunction() {
        Android.showDashBoard();
    }
</script>

Answer 1

尝试设置

View layout = inflater.inflate(R.layout.dashboard_dialog, (ViewGroup) findViewById(R.id.layout_root));

到

View layout = inflater.inflate(R.layout.dashboard_dialog, null);

我发现将 View 附加到容器很少(如果有的话)有效，并且假设“layout_root”与您的 Activity 有关，对话框无论如何都无法找到此 View 。