android - 单例构造函数使我的应用程序崩溃

Question

我正在测试应用程序的模型层，并且想向列表中添加元素。但是，每当我尝试向数据模型中添加一些数据时，应用程序就会崩溃。我找不到原因。

我的数据模型代码。

public class DataModel {


private List<Log> logs;
private static DataModel instance;
private Context ctx;


//Singleton constructor
private DataModel()
{
   //This makes it crash
   logs.add(new Log("1234","sms", 123545, 1, 0));

   //Load logs from database - Not done yet.

}

public static DataModel getInstance()
{
    if (instance == null)
    {
        //Creates the instance
        instance = new DataModel();
    }
    return instance;
}

我的日志代码

public class Log {


private String phonenumber;
private String type;
private long date;
private int incoming;
private int outgoing;
private long id;

//Constructor for incoming sms or call
public Log( String Phonenumber, String Type, long Date, int Incoming, int Outgoing)
{

    this.phonenumber = Phonenumber;
    this.type = Type;
    this.date = Date;
    this.incoming = Incoming;
    this.outgoing = Outgoing;
}


public long getId()
{
    return id;
}

public void setId(long id)
{
    this.id = id;
}

public String getPhonenumber()
{
    return phonenumber;
}

public void setPhonenumer(String phonenumber)
{
    this.phonenumber = phonenumber;
}

public String getType()
{
    return type;
}

public void setType(String type)
{
    this.type = type;
}

public long getDate()
{
    return date;
}

public void setDate(long date)
{
    this.date = date;
}

public int getIncoming()
{
    return incoming;
}

public void setIncoming(int incoming)
{

    this.incoming = incoming;

}

public int getOutgoing()
{
    return outgoing;
}

public void setOutgoing (int outgoing)
{

    this.outgoing = outgoing;
}

Answer 1

您没有初始化logs。执行以下语句时其null:

logs.add(new Log("1234","sms", 123545, 1, 0));

更改:

private List<Log> logs;

至:

private List<Log> logs = new ArrayList<Log>();