控制android弹出框不消失(用到反射的方法)

Android中的弹出框在被点击时， 无论点击哪个按钮都会关闭窗口。 但是有的情况下我们不需要立即关闭窗口。下面的情况是弹出框中要求用户输入文件名， 并在点击确定时检查文件名的合法性， 不合法则提示用户重新输入， 弹出框要保持在界面上。 点击取消时弹出框消失。 这里通过对控件的反射来实现： 
/**our button handler**/ 
    private ButtonHandler bHandler; 

//pop up dialog with own button handler 
    private void popUpDialog(AlertDialog dialog) { 
        /* 
         * alert dialog's default handler will always close dialog whenever user 
         * clicks on which button. we have to replace default handler with our 
         * own handler for blocking close action. 
         * Reflection helps a lot. 
         */ 
        try { 
            Field field = dialog.getClass().getDeclaredField("mAlert"); 
            field.setAccessible(true); 
            
            //retrieve mAlert value 
            Object obj = field.get(dialog); 
            field = obj.getClass().getDeclaredField("mHandler"); 
            field.setAccessible(true); 
            //replace mHandler with our own handler 
            field.set(obj, bHandler); 
        } catch (SecurityException e) { 
            Debug.error(e.getMessage()); 
        } catch (NoSuchFieldException e) { 
            Debug.error(e.getMessage()); 
        } catch (IllegalArgumentException e) { 
            Debug.error(e.getMessage()); 
        } catch (IllegalAccessException e) { 
            Debug.error(e.getMessage()); 
        } 
        
        //we can show this dialog now. 
        dialog.show(); 
    } 
    /* 
     * define our own button handler, do not deal with dismiss message. 
     */ 
    class  ButtonHandler  extends  Handler { 

         private  WeakReference<DialogInterface> mDialog; 

         public ButtonHandler(DialogInterface dialog) { 
            mDialog = new WeakReference<DialogInterface>(dialog); 
         } 

         public void handleMessage(Message msg) { 
             switch (msg.what) { 
                 case DialogInterface.BUTTON_POSITIVE: 
                 case DialogInterface.BUTTON_NEGATIVE: 
                 case DialogInterface.BUTTON_NEUTRAL: 
                    ((DialogInterface.OnClickListener) msg.obj).onClick(mDialog 
                            .get(), msg.what); 
                     break ; 
            } 
        } 
    } 

然后创建一个AlertDialog时如下去调用： 
//create dialog 
            mDialog = new AlertDialog.Builder(mContext) 
            .setView(selectImageView) 
            .setNegativeButton(android.R.string.cancel, mOnDialogClickListener) 
            .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() { 
                public void onClick(DialogInterface dialog, int arg1) { 
                    //check input file name 
                    if (isValidFileName(fileNameInput.getText().toString())) { 
                        String fileName = fileNameInput.getText().toString().trim(); 
                        mediaList.get(0).setName(fileName); 
                        saveMedia(mediaList); 
                        dialog.dismiss(); 
                    } else { 
                        Toast.makeText(mContext, R.string.invalid_file_name, 1500).show(); 
                    } 
                    
                } 
            }).create(); 
mOnDialogClickListener用来处理关闭窗口事件： 
/* 
     * cancel dialog listener 
     */ 
    OnClickListener mOnDialogClickListener = new DialogInterface.OnClickListener() { 
        public void onClick(DialogInterface dialog, int buttonId) { 
            switch (buttonId) { 
                case DialogInterface.BUTTON_NEGATIVE: 
                    dialog.dismiss(); 
                    break; 
                case DialogInterface.BUTTON_POSITIVE: 
                    
                    break; 
            } 
            
        } 
    };