有一个叫做圆圈的课。它包含circleID，circleGeometry和circlePath属性。
public class Circle
{
public string ID {get; set;}
public EllipseGeometry circleGeometry {get; set;}
public Path circlePath {get; set;}
}
现在，我尝试为圆圈设置ZIndex值。例如，它将是2。
Canvas.SetZIndex(someCircleID.circlePath,2);
但我有这样的警告：
＆＃34;通过派生类型＆＃34;
调用静态方法
有人可以解释一下这是什么意思吗？
答案 0 :(得分：8)
SetZIndex在Panel类上定义，Canvas派生自SetZIndex。编译器正在生成警告，说明您在子类型上使用静态方法。这不是一个真正的问题，但在某些方面使用时可能会导致混淆。由于var ftpRequest = (FtpWebRequest) HttpWebRequest.Create("ftp://my.ftp.com");
无效返回，这不应该是一个问题。
但想象一下：
Create WebRequest实际上是HttpWebRequest的静态方法，但在FtpWebRequest上使用，因为它是派生类型，而可能这样做。所以，您希望它是一个正在生成的Web请求，对吗？但它不是，它会生成SetZIndex，因为它在URI中指定。
修改
我想指出的是，通常情况下，编译器警告是有原因的，也就是存在这种情况。只要在Canvas类中没有创建Canvas的重载，呼叫就是安全的。但正如@SriramSakthivel在评论中指出的那样，如果在此过程中，您或其他任何人在new类（使用 import java.text.DateFormat;
import java.text.ParseException;
import java.text.SimpleDateFormat;
import java.util.Calendar;
import java.util.Date;
import java.util.TimeZone;
import android.app.Activity;
import android.app.AlarmManager;
import android.app.DatePickerDialog;
import android.app.Dialog;
import android.content.BroadcastReceiver;
import android.content.Context;
import android.content.Intent;
import android.content.IntentFilter;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.CalendarView;
import android.widget.DatePicker;
import android.widget.DatePicker.OnDateChangedListener;
import android.widget.TextView;
import android.widget.Toast;
public class DatePickerExample extends Activity {
private TextView Output;
private Button changeDate;
private Boolean mEnableNativeCalGridView = null;
String timeZone;
public static TimeZone tz;
private int year;
private int month;
DatePickerDialog d;
public Calendar c;
SimpleDateFormat sdf;
private int day;
public static IntentFilter s_intentFilter;
static final int DATE_PICKER_ID = 1111;
static{
s_intentFilter = new IntentFilter();
s_intentFilter.addAction(Intent.ACTION_TIME_TICK);
s_intentFilter.addAction(Intent.ACTION_TIMEZONE_CHANGED);
s_intentFilter.addAction(Intent.ACTION_TIME_CHANGED);
}
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
registerReceiver(m_timeChangedReceiver, s_intentFilter);
Output = (TextView) findViewById(R.id.Output);
changeDate = (Button) findViewById(R.id.changeDate);
// sdf = new SimpleDateFormat("EEE, MMM d, ''yy");//Wed, Jul 4, '01
// Show current date
Output.setText(new StringBuilder()
// Month is 0 based, just add 1
.append(month + 1).append("-").append(day).append("-")
.append(year).append(" "));
// Button listener to show date picker dialog
changeDate.setOnClickListener(new OnClickListener() {
@SuppressWarnings("deprecation")
@Override
public void onClick(View v) {
// On button click show datepicker dialog
showDialog(DATE_PICKER_ID);
}
});
}
@Override
protected void onPrepareDialog(int id, Dialog dialog) {
switch (id) {
case DATE_PICKER_ID:
((DatePickerDialog) dialog).updateDate(
c.get(Calendar.YEAR),
c.get(Calendar.MONTH),
c.get(Calendar.DAY_OF_MONTH));
}
}
@Override
protected Dialog onCreateDialog(int id) {
switch (id) {
case DATE_PICKER_ID:
// open datepicker dialog.
// set date picker for current date
// add pickerListener listner to date picker
sdf = new SimpleDateFormat("EEE MMM dd HH:mm:ss z yyyy");
tz = TimeZone.getDefault();
System.out.println("TimeZone "+tz.getDisplayName(false, TimeZone.SHORT)+" Timezon id :: " +tz.getID());
timeZone = tz.getDisplayName(false, TimeZone.SHORT);
c= Calendar.getInstance();
c.setTimeZone(tz);
year = c.get(Calendar.YEAR);
month = c.get(Calendar.MONTH);
day = c.get(Calendar.DAY_OF_MONTH);
d = new DatePickerDialog(DatePickerExample.this, pickerListener, year, month,day);
setMinMaxdate();
return d;
}
return null;
}
////////////////////Fix for issue on OS 5.1 //////////////////////
public long getDateFormatted(String date){
String givenDateString = date;
long timeInMilliseconds = 0;
try {
Date mDate = sdf.parse(givenDateString);
timeInMilliseconds = mDate.getTime();
System.out.println("Date in milli :: " + timeInMilliseconds);
} catch (ParseException e) {
e.printStackTrace();
}
return timeInMilliseconds;
}
//////////////////////////////////////////
private DatePicker.OnDateChangedListener newchange= new OnDateChangedListener(){
@Override
public void onDateChanged(DatePicker view,
int year, int monthOfYear,int dayOfMonth) {
Toast.makeText(getApplicationContext(),
"onDateChanged", Toast.LENGTH_SHORT).show();
}};
DatePicker datePicker;
public void setMinMaxdate() {
//Time zone calculation
//TimeZone.setDefault(tz);
///////////////////////
long calEvtEndDate= getDateFormatted("Sun May 31 23:59:59 "+timeZone+" 2015");//System.currentTimeMillis();
long calEvtStartDate= getDateFormatted("Wed May 13 00:00:00 "+timeZone+" 2015");//System.currentTimeMillis()/2;
// long calEvtEndDate = getDateFormatted("Sun, may 31, '15");
//long calEvtStartDate = getDateFormatted("Wed, may 13, '15");
if(d != null){
datePicker = d.getDatePicker();
if(mEnableNativeCalGridView != null){
datePicker.setCalendarViewShown(mEnableNativeCalGridView.booleanValue());
}
// If Start Date is Greater than End Date then we are showing from valid StartDate
// value and we are not setting the maxdate.
if (calEvtStartDate > calEvtEndDate) {
datePicker.setMinDate(calEvtStartDate);
} else {
if (calEvtStartDate > 0) { // If Only ValidStart date is provided, then setting the minDate.
datePicker.setMinDate(calEvtStartDate);
}
if (calEvtEndDate > 0) { // If Only ValidEnd date is provided, then setting the maxDate.
datePicker.setMaxDate(calEvtEndDate);
}
}
}
}
@Override
protected void onResume() {
// TODO Auto-generated method stub
super.onResume();
System.out.println("-------resumed");
}
public DatePickerDialog.OnDateSetListener pickerListener = new DatePickerDialog.OnDateSetListener() {
// when dialog box is closed, below method will be called.
@Override
public void onDateSet(DatePicker view, int selectedYear,
int selectedMonth, int selectedDay) {
//view.updateDate(year, month, day);
System.out.println("---------------datesetchange");
year = selectedYear;
month = selectedMonth;
day = selectedDay;
// Show selected date
Output.setText(new StringBuilder().append(month + 1)
.append("-").append(day).append("-").append(year)
.append(" "));
}
};
public void onDestroy() {
super.onDestroy();
unregisterReceiver(m_timeChangedReceiver);
}
private final BroadcastReceiver m_timeChangedReceiver = new BroadcastReceiver() {
@Override
public void onReceive(Context context, Intent intent) {
final String action = intent.getAction();
if (action.equals(Intent.ACTION_TIME_CHANGED) ||
action.equals(Intent.ACTION_TIMEZONE_CHANGED))
{
System.out.println("timezone changed---"+action.toString());
tz = TimeZone.getDefault();
System.out.println("TimeZone "+tz.getDisplayName(false, TimeZone.SHORT)+" Timezon id :: " +tz.getID());
timeZone = tz.getDisplayName(false, TimeZone.SHORT);
// Intent intent1 = getIntent();
// finish();
// startActivity(intent1);
showDialog(DATE_PICKER_ID);
}
}
};
}修饰符）中添加了任何扩展方法或静态方法，它将会不再输出所需的结果，你必须意识到这一点。
答案 1 :(得分：2)
这意味着方法SetZIndex是在类Canvas的基类型上定义的，但您可以使用后者来调用它。你最好使用基类。