android context 空指针 问题

Question

LoginDialog l=new LoginDialog();

l.LoginDialog2(M.this);
我写了个LoginDialog类 如下 结果 老是 报错

            public class LoginDialog extends Activity implements OnClickListener {
private Context mcontext=null;
 public void LoginDialog2 (Context context) {  

        this.mcontext = context;  

        LayoutInflater layoutInflater = LayoutInflater.from(context);  
        View longinDialogView = layoutInflater.inflate(MResource.getIdByName(getApplication(), "layout", "logindialog"), null);  

        //获取布局中的控件  
        EditText mUserName = (EditText)longinDialogView.findViewById( MResource.getIdByName(getApplication(), "id", "edit_username"));  
        EditText  mPassword = (EditText)longinDialogView.findViewById( MResource.getIdByName(getApplication(), "id", "edit_password"));  

        //创建一个AlertDialog对话框  
        AlertDialog longinDialog = new AlertDialog.Builder(context)  
            .setTitle("登录框")  
            .setView(longinDialogView)                //加载自定义的对话框式样  
            .setPositiveButton("确定",  this)  
            .setNeutralButton("取消", this)  
            .create();    

        longinDialog.show();
    }
@Override
public void onClick(DialogInterface arg0, int arg1) {
    // TODO Auto-generated method stub

} 

}
错误提示 java.lang.NullPointerException

Answer 1

你没有走构造，context是怎么传进来呢