alertDialog.getButton()方法给出了空指针异常android

Question

我打算用layout_weight = 1创建3个按钮,对自定义对话框不感兴趣.所以我写了下面的代码.它不工作.总是是按钮给我null.这段代码怎么了？

  AlertDialog dialog= new AlertDialog.Builder(this).create();
            dialog.setIcon(R.drawable.alert_icon);
            dialog.setTitle("title");
            dialog.setMessage("Message");
            dialog.setButton(AlertDialog.BUTTON_POSITIVE,"Yes", new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface arg0, int arg1) {
                                                }
            });
            Button yesButton = dialog.getButton(AlertDialog.BUTTON_POSITIVE);
            Log.w("Button",""+yesButton);//here getting null
            LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT, 1f);
            yesButton.setLayoutParams(layoutParams);
            dialog.show();

此致,Android开发人员.

Answer 1

在这里查看答案:http://code.google.com/p/android/issues/detail？id = 6360

正如评论#4中所述,您必须先调用show()对话框才能访问按钮,但事先无法使用它们.有关如何在准备就绪后立即修改按钮的自动解决方案,请参阅Mickeys应答

Answer 2

这对我有用:

AlertDialog alertDialog = new AlertDialog.Builder(this)
                .setMessage(message)
                .setCancelable(true)
                .setPositiveButton("Yes",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                            //do smthng
                        })
                .setNegativeButton("No", new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        //do snthn
                    }
                }).create();

        alertDialog.setOnShowListener(new OnShowListener() {
            @Override
            public void onShow(DialogInterface dialog) {                    //
                Button positiveButton = ((AlertDialog) dialog)
                        .getButton(AlertDialog.BUTTON_POSITIVE);
                positiveButton.setBackgroundDrawable(getResources()
                        .getDrawable(R.drawable.btn_default_holo_dark));

                Button negativeButton = ((AlertDialog) dialog)
                        .getButton(AlertDialog.BUTTON_NEGATIVE);
                positiveButton.setBackgroundDrawable(getResources()
                        .getDrawable(R.drawable.btn_default_holo_dark));
            }
        });

        alertDialog.show(); 

只有在这个顺序,可以调用alertDialog.setOnShowListener后create()

Answer 3

谢谢维厄。但是为了新开发人员的理解目的，我正在下面重写代码

AlertDialog dialog= new AlertDialog.Builder(this).create();             
dialog.setIcon(R.drawable.alert_icon);             
dialog.setTitle("title");            
dialog.setMessage("Message");             
dialog.setButton(AlertDialog.BUTTON_POSITIVE,"Yes", new DialogInterface.OnClickListener() {                 
    @Override                 
    public void onClick(DialogInterface arg0, int arg1) {                                                
    }             
}); 
dialog.show(); 
Button yesButton = dialog.getButton(AlertDialog.BUTTON_POSITIVE);             
Log.w("Button",""+yesButton); //here getting null             
LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(LayoutParams.FILL_PARENT, LayoutParams.WRAP_CONTENT, 1f);             
yesButton.setLayoutParams(layoutParams);