我是一个初学者安卓程序员,我有这个问题。
我有一个课程如下...
import java.util.Calendar;
import android.app.AlertDialog;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.os.Bundle;
import android.widget.DatePicker;
public class DatePickerFragment extends DialogFragment implements
DatePickerDialog.OnDateSetListener {
private int year;
private int month;
private int day;
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Use the current date as the default date in the picker
final Calendar c = Calendar.getInstance();
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH);
int day = c.get(Calendar.DAY_OF_MONTH);
// Create a new instance of DatePickerDialog and return it
return new DatePickerDialog(getActivity(),
AlertDialog.THEME_DEVICE_DEFAULT_DARK, this, year, month, day);
}
public void onDateSet(DatePicker view, int year, int month, int day) {
this.setYear(year);
this.setMonth(month);
this.setDay(day);
System.out.println(day+""+month+""+year);
// Do something with the date chosen by the user
}
public int getYear() {
return year;
}
public void setYear(int year) {
this.year = year;
}
public int getMonth() {
return month;
}
public void setMonth(int month) {
this.month = month;
}
public int getDay() {
return day;
}
public void setDay(int day) {
this.day = day;
}
}
在我的主要活动中,我有一个带有侦听器的按钮,当我按下它时,它会调用这个类并调出对话框/日期选择器,如下所示:
setDoBButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
DatePickerFragment newFragment = new DatePickerFragment();
newFragment.show(getFragmentManager(), "datePicker");
}
});
我的问题是,一旦我单击按钮并出现对话框,在我设置日期并调用onDateSet
后,我无法使用我的 getter 将日期分配给我的主要活动中的任何变量,因为onclick
没有等待我完成在对话框中设置日期。
例如,如果我的听众是这样的...
setDoBButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
DatePickerFragment newFragment = new DatePickerFragment();
newFragment.show(getFragmentManager(), "datePicker");
int x = newFragment.getDay();
}
});
它不起作用,因为对话框将显示,然后getDay
会立即被调用,因为它在onclick
但尚未在对话框中设置日期。那么我该如何解决这个问题呢?
非常感谢。
使用接口。
在 DatePickerFragment
中定义接口。在活动类中实现接口并使用相同的接口。
检查"与活动通信"下的主题。
http://developer.android.com/guide/components/fragments.html
例:
public class MainActivity extends Activity implements DatePickerFragment.TheListener{
Button b;
TextView tv;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b= (Button) findViewById(R.id.button1);
tv= (TextView) findViewById(R.id.textView1);
b.setOnClickListener(new OnClickListener()
{
@Override
public void onClick(View arg0) {
// TODO Auto-generated method stub
DialogFragment picker = new DatePickerFragment();
picker.show(getFragmentManager(), "datePicker");
}
});
}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.main, menu);
return true;
}
@Override
public void returnDate(String date) {
// TODO Auto-generated method stub
tv.setText(date);
}
}
日期选取器片段
public class DatePickerFragment extends DialogFragment
implements DatePickerDialog.OnDateSetListener {
TheListener listener;
public interface TheListener{
public void returnDate(String date);
}
@Override
public Dialog onCreateDialog(Bundle savedInstanceState) {
// Use the current date as the default date in the picker
final Calendar c = Calendar.getInstance();
int year = c.get(Calendar.YEAR);
int month = c.get(Calendar.MONTH);
int day = c.get(Calendar.DAY_OF_MONTH);
listener = (TheListener) getActivity();
// Create a new instance of DatePickerDialog and return it
return new DatePickerDialog(getActivity(), this, year, month, day);
}
@Override
public void onDateSet(DatePicker view, int year, int month, int day) {
Calendar c = Calendar.getInstance();
c.set(year, month, day);
SimpleDateFormat sdf = new SimpleDateFormat("yyyy-MM-dd");
String formattedDate = sdf.format(c.getTime());
if (listener != null)
{
listener.returnDate(formattedDate); // instead of date set the day
}
}
}
在上面的例子中,你在DaterPicker中有接口
public interface TheListener{
public void returnDate(String date);
}
然后
listener.returnDate(formattedDate);
然后在活动类中实现侦听器
implements DatePickerFragment.TheListener
实现该方法
@Override
public void returnDate(String date) {
// TODO Auto-generated method stub
tv.setText(date); // date is available here
}
创建一个名为 assign 变量或类似方法的方法并在onclick
调用该方法
setDoBButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
DatePickerFragment newFragment = new DatePickerFragment();
newFragment.show(getFragmentManager(), "datePicker");
assign_variables();
}
});
private void assign_variables(){
int x = newFragment.getDay();
}
或
创建类似go_on
的static class variable
private static final boolean go_on = true;
现在在你onclick
添加一个无限循环
setDoBButton.setOnClickListener(new OnClickListener() {
public void onClick(View v) {
DatePickerFragment newFragment = new DatePickerFragment();
newFragment.show(getFragmentManager(), "datePicker");
while(go_on){}
}
});
然后随心所欲地完成作业
int x = newFragment.getDay();
int y = newFragment.getTime();
go_on = false; //and set the boolean to false
现在它将打破 while 循环,您可以获得分配的内容
注意:只要确保你不会以一些死锁或ANR错误告终