Android - 自定义对话框在定义多个按钮时抛出NullPointerException

Question

这是定义我的自定义对话框的代码。当我显示此对话框时，它会在注释行中抛出NullPointerException。

    protected Dialog onCreateDialog (int id) {
    Dialog dialog = null;
        switch (id) {
        case DIALOG_SUCCESS_ID:

            Context thisContext = this;

            dialog = new Dialog(thisContext);

            dialog.setContentView(R.layout.win_dialog);
            dialog.setTitle("Stage One");

            TextView timeScore = (TextView) dialog.findViewById(R.id.TimeScore);
            timeScore.setText (elapsedTimeSec + "s");
            TextView bestScore = (TextView) dialog.findViewById(R.id.BestScore);
            bestScore.setText ("Best Score: (n/a)");

            Button retry = (Button) dialog.findViewById(R.id.Retry);
            retry.setOnClickListener(new View.OnClickListener() {
                public void onClick (View v) {
                    Intent retry = new Intent(v.getContext(), LevelOne.class);
                    startActivityForResult(retry, 0);
                    finish();
                }
            });

            Button menu = (Button) dialog.findViewById (R.id.ReturnToMenu);

            //Throws NullPointerException at this line
            menu.setOnClickListener(new View.OnClickListener() {
                public void onClick (View v) {
                    Intent menu = new Intent(v.getContext(), Menu.class);
                    startActivityForResult(menu, 0);
                    finish();
                }
            });
            break;
        case DIALOG_GAMEOVER_ID:
            break;
        default:
            dialog = null;
        }
        return dialog;
}

但是当我删除菜单按钮和menu.SetOnClickListener（）方法时，它工作正常！我的重试按钮也顺利工作。为什么我不能添加多个按钮？为什么会抛出异常？

Answer 1

看起来dialog.findViewById (R.id.ReturnToMenu);返回null。你能检查一下你确实有一个ID正确的按钮吗？我猜你的“返回菜单”按钮ID中有一个错字。