如何禁用AlertDialog内的按钮？跟进问题

Question

我昨天问了这个问题(http://stackoverflow.com/questions/7392321/how-do-you-disable-a-button-inside-of-an-alertdialog)并相应地修改了我的代码...今天早上我跑了模拟器中的代码并收到了NPE.这是代码:

public void monster() {
        int playerint = settings.getPlayerInt();
        int monsterint = settings.getMonsterInt();



        AlertDialog.Builder alertbox = new AlertDialog.Builder(this);
        alertbox.setMessage("You have Encountered a Monster");

        alertbox.setPositiveButton("Fight!",
                new DialogInterface.OnClickListener() {

                    // do something when the button is clicked
                    public void onClick(DialogInterface arg0, int arg1) {
                        createMonster();
                        fight();

                    }
                });

        alertbox.setNeutralButton("Try to Outwit",
                new DialogInterface.OnClickListener() {

                    // do something when the button is clicked
                    public void onClick(DialogInterface arg0, int arg1) {
                        // This should not be static
//                      createTrivia();
                        trivia();

                    }
                });

        // Return to Last Saved CheckPoint
        alertbox.setNegativeButton("Run Away!",
                new DialogInterface.OnClickListener() {

                    // do something when the button is clicked
                    public void onClick(DialogInterface arg0, int arg1) {
//                      runAway();
                    }
                });

这就是问题出现的地方

// show the alert box
            alertbox.show();
            AlertDialog dialog = alertbox.create();
            Button button = dialog.getButton(AlertDialog.BUTTON_NEUTRAL);
            if(monsterint > playerint) {
                button.setEnabled(false);
            }
        }

谁知道我做错了什么？

Answer 1

你有两个问题.第一个是你应该调用show(),并create()分别这样.你实际做的是隐式创建一个AlertDialog并显示它alertbox.show(),然后在它下面创建一个AlertDialog你用来操作按钮的秒.让我们尽量保持对Builder的直接调用.

而且,更直接的原因是你的NPE崩溃,在AlertDialog陆地上按钮本身实际上并没有被创建,直到AlertDialog准备好显示(基本上,之后AlertDialog.show()被称为......再次,不要与AlertDialog.Builder.show()方法混淆).为了AlertDialog您的目的,您需要在显示对话框后获取并操作按钮状态.以下是对最终代码部分的修改,修复了此问题:

//Create the AlertDialog, and then show it
AlertDialog dialog = alertbox.create();
dialog.show();
//Button is not null after dialog.show()
Button button = dialog.getButton(AlertDialog.BUTTON_NEUTRAL);
if(monsterint > playerint) {
    button.setEnabled(false);
}

HTH