Question

这是我的代码

@Override
public void onClick(View v) {
final AlertDialog.Builder adb = new AlertDialog.Builder(getApplicationContext());
adb.setView(LayoutInflater.from(getApplicationContext()).inflate(R.layout.custom, null));

adb.setPositiveButton("Add",new android.content.DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int arg1) {

                DatePicker datePicker = (DatePicker)findViewById(R.id.datePicker);

                java.util.Date date = null;
                Calendar cal = GregorianCalendar.getInstance();
                cal.set(datePicker.getYear(),datePicker.getMonth(), datePicker.getDayOfMonth());
                date = cal.getTime();
            }                  
        });             
adb.show();
}

我在这行中有NullPointerException，我认为datePicker不是findById，因为我使用AlertDialog.Builder。

cal.set（datePicker.getYear（），datePicker.getMonth（），datePicker.getDayOfMonth（））;

我尝试使用adb.findViewById();，但这是一个错误（方法findViewById（int）未定义类型AlertDialog.Builder）。你能帮帮我吗？

Answer 1

更改

DatePicker datePicker = (DatePicker)findViewById(R.id.datePicker);

这一行

DatePicker datePicker = (DatePicker)adb.findViewById(R.id.datePicker);

...............

试试这个：

final AlertDialog.Builder adb = new AlertDialog.Builder(this);
final View view = LayoutInflater.from(getApplicationContext()).inflate(R.layout.main1, null);
adb.setView(view);
final Dialog dialog;
adb.setPositiveButton("Add",new android.content.DialogInterface.OnClickListener() {
    public void onClick(DialogInterface dialog, int arg1) {

        DatePicker datePicker = (DatePicker)view.findViewById(R.id.datePicker1);

        java.util.Date date = null;
        Calendar cal = GregorianCalendar.getInstance();
        cal.set(datePicker.getYear(),datePicker.getMonth(), datePicker.getDayOfMonth());
        date = cal.getTime();
    }                  
});   
dialog = adb.create();
dialog.show();

Answer 2

使用DatePicker参数搜索dialog：

DatePicker datePicker = (DatePicker) ((Dialog) dialog).findViewById(R.id.datePicker);

Answer 3

我认为这可能是问题，

final AlertDialog.Builder adb = new AlertDialog.Builder(getApplicationContext());
adb.setView(LayoutInflater.from(getApplicationContext()).inflate(R.layout.custom,null));

使用以下方法为视图充气并使用视图对象获取ID。

 LayoutInflater factory = LayoutInflater.from(this);
    final View textEntryView = factory.inflate(R.layout.alert_dialog_text_entry, null);

DatePicker datePicker = (DatePicker)textEntryView.findViewById(R.id.datePicker1);

示例：

protected Dialog onCreateDialog() {
    LayoutInflater factory = LayoutInflater.from(this);
    final View textEntryView = factory.inflate(R.layout.alert_dialog_text_entry, null);
    return new AlertDialog.Builder(TicTacToe.this)
        //.setIconAttribute(android.R.attr.alertDialogIcon)
        .setTitle(getTitleText())
        .setView(textEntryView)
        .setPositiveButton("JOIN GAME", new DialogInterface.OnClickListener() {
            public void onClick(DialogInterface dialog, int whichButton) {
                try
                {
                    EditText et = (EditText)findViewById(R.id.username_edit);
                        playerName = et.getText().toString();
                }
                catch (Exception e)
                {
                }
            }
        })
        .create();
return null;

}

Answer 4

In my case: First I must call the

dialog.show(),

and only after it I was able to use

dialog.findviewById(R.id.myID).

If I missed to call the show(), than I got a null back with findViewByID.

Answer 5

项目清理和重建为我修复了这个错误（在Xamarin上）。

在AlertDialog.Builder中使用findViewById（）时出现NullPointerException

5 个答案: