Question

我有一个类

类别：StatusEventChangeDto ::

public class StatusEventChangeDto {

    protected String address;
    DutyState status;
    protected double latitude,longitude;
    protected long time;



    public StatusEventChangeDto()
    {}

    public StatusEventChangeDto(double latitude, double longitude, String address, long time, DutyState status)
    {
        this.latitude = latitude;
        this.longitude = longitude;
        this.address = address;
        this.time = time;
        this.status = status;
    }

    public String getAddress() {
        return address;
    }

    public void setAddress(String address) {
        this.address = address;
    }

    public long getTime() {
        return time;
    }

    public void setTime(long time) {
        this.time = time;
    }

    public DutyState getStatus() {
        return status;
    }

    public void setStatus(DutyState status) {
        this.status = status;
    }
    public double getLatitude() {
        return latitude;
    }

    public void setLatitude(double latitude) {
        this.latitude = latitude;
    }

    public double getLongitude() {
        return longitude;
    }

    public void setLongitude(double longitude) {
        this.longitude = longitude;
    }

    @Override
    public String toString()
    {
        StringBuffer sb = new StringBuffer();
        sb.append("Lat : "+latitude+"\n");
        sb.append("Long : "+longitude+"\n");
        sb.append("Address : "+address+"\n");
        sb.append("Time : "+time+"\n");
        sb.append("Status : "+status+"\n");
        return sb.toString();
    }
}

还有一个课程

类别：StatusEventDurationChangeDto

public class StatusEventDurationChangeDto extends StatusEventChangeDto
{
    private Duration duration;

    public StatusEventDurationChangeDto()
    {
    }

    public Duration getDuration() {
        return duration;
    }

    public void setDuration(Duration duration) {
        this.duration = duration;
    }

    public String toString() {

        StringBuffer sb = new StringBuffer(super.toString());

        PeriodFormatter formatter = new PeriodFormatterBuilder()
                .appendHours()
                .appendSuffix("h")
                .appendMinutes()
                .appendSuffix("m")
                .toFormatter();
        String formatted = formatter.print(duration.toPeriod());
        sb.append("Duration : "+formatted+"\n");

        return sb.toString();
    }
}

我在这里输入类似于上面的两个类似

StatusEventChangeDto event1 = new StatusEventChangeDto(17.45, 78.45, "hyderabad, Telangana", now.minusHours(1).getMillis(), ONDUTY);
StatusEventChangeDto event2 = new StatusEventChangeDto(17.48, 78.50, "hyderabad, Telangana", now.minusHours(2).getMillis(), OFFDUTY);



StatusEventDurationChangeDto duration1 = (StatusEventDurationChangeDto)event1;
 duration1.setDuration(new Duration(now, now.minusHours(1)));
 StatusEventDurationChangeDto duration2 = (StatusEventDurationChangeDto) event2;
 duration2.setDuration(new Duration(now, now.minusHours(2)));

当我运行这个时，我得到了类型转换异常

帮助我的家伙

Answer 1

您无法将event1和event1投射到StatusEventDurationChangeDto，因为此变量已链接到对象StatusEventChangeDto的实例，但不会延伸StatusEventDurationChangeDto反之亦然

Answer 2

问题在于：

StatusEventDurationChangeDto duration1 =（StatusEventDurationChangeDto）event1;

您无法将event1 / 2的对象强制转换为StatusEventDurationChangeDto，因为event1 / event2属于StatusEventChangeDto类型（您自己定义的类）

我认为您应该将该课程视为＆＃34; USER DEFINED DATA TYPE＆＃34;。您应该首先采用类和类型转换的完整概念。

Answer 3

你有

StatusEventDurationChangeDto将StatusEventChangeDto扩展为

表示StatusEventDurationChangeDto是一个StatusEventChangeDto，因此您可以将StatusEventDurationChangeDto强制转换为StatusEventChangeDto，但不能将StatusEventChangeDto强制转换为StatusEventDurationChangeDto。

一般规则是，您可以在层次结构中向下投射某些东西而不是反过来。

如何在Android中输入类型？

3 个答案: