为什么从 Java 添加到 Android 中的 SQLite 数据库的日期值始终为空？

Question

我绝对是 Android 的初学者。我在处理 Android 中的日期时遇到问题。现在我将一个值从 EditText 字段插入到 SQLite table 列，该列是日期数据库日期。添加到数据库时它始终为空。我的代码有什么问题？

我的数据库助手class

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "todo.db";
    private static final String TABLE_NAME = "task";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_DESCRIPTION = "description";
    private static final String COLUMN_DATE ="date";
    private static final String COLUMN_DONE = "done";
    private static final String CREATE_TABLE = "CREATE TABLE "+TABLE_NAME+" ("+COLUMN_ID+" INTEGER PRIMARY KEY AUTOINCREMENT,"+COLUMN_DESCRIPTION+" TEXT,"+
    COLUMN_DATE+" DATE,"+COLUMN_DONE+" BOOLEAN)";
    SQLiteDatabase db;

    public DatabaseHelper(Context context)
    {
        super(context,DATABASE_NAME,null,DATABASE_VERSION);
    }


    @Override
    public void onCreate(SQLiteDatabase db)
    {
        this.db = db;
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String query = "DROP TABLE IF EXISTS "+TABLE_NAME;
        db.execSQL(query);
        this.onCreate(db);
    }

    public  void insertTask(Task task)
    {
        db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_DESCRIPTION,task.getDescription());
        values.put(COLUMN_DATE,task.getDate().toString());
        values.put(COLUMN_DONE,Boolean.FALSE.toString());
        db.insert(TABLE_NAME, null, values);
        db.close();
    }
}

这是我在Fragment中的保存方法

public void saveTask()
    {
        String description = tfDescription.getText().toString();
        String date = tfDate.getText().toString();

        if(description.isEmpty())
        {
            Toast.makeText(getActivity().getBaseContext(),"Description is required",Toast.LENGTH_SHORT).show();
        }
        else if(date.isEmpty())
        {
            Toast.makeText(getActivity().getBaseContext(),"Date is required",Toast.LENGTH_SHORT).show();
        }
        else if(description.length()<getResources().getInteger(R.integer.min_description_length))
        {
            String minChar = String.valueOf(getResources().getInteger(R.integer.min_description_length));
            Toast.makeText(getActivity().getBaseContext(),"Description should be minium "+minChar+" characters",Toast.LENGTH_SHORT).show();
        }
        else{
            //check date
            SimpleDateFormat format = new SimpleDateFormat("MM/dd/yyyy");
            boolean parseOk = false;
            Date taskDate = new Date();
            try{
                taskDate = format.parse(date);
                Task task = new Task();
                task.setDescription(description);
                task.setDate(taskDate);
                dbHelper.insertTask(task);
                parseOk = true;
            }
            catch(ParseException e)
            {
                parseOk = false;
            }

            if(parseOk)
            {
                //insert task to database
                Toast.makeText(getActivity().getBaseContext(),"Task saved",Toast.LENGTH_SHORT).show();
            }
            else{
                Toast.makeText(getActivity().getBaseContext(),"Invalid date format",Toast.LENGTH_SHORT).show();
            }
        }
    }

这是我的任务class

public class Task {
    private int Id;
    private String Description;
    private java.util.Date TaskDate;
    private boolean Done;

    public void setId(int Id)
    {
        this.Id = Id;
    }

    public int getId()
    {
        return this.Id;
    }

    public void setDescription(String Description)
    {
        this.Description = Description;
    }

    public String getDescription()
    {
        return this.Description;
    }

    public void setDate(Date taskDate)
    {
        this.TaskDate = taskDate;
    }

    public Date getDate(){
        return this.TaskDate;
    }

    public void setDone(Boolean done)
    {
        this.Done = done;
    }

    public Boolean getDone()
    {
        return this.Done;
    }
}

这是我完整的 DatabaseHelper class

public class DatabaseHelper extends SQLiteOpenHelper {

    private static final int DATABASE_VERSION = 1;
    private static final String DATABASE_NAME = "todo.db";
    private static final String TABLE_NAME = "task";
    private static final String COLUMN_ID = "id";
    private static final String COLUMN_DESCRIPTION = "description";
    private static final String COLUMN_DATE ="date";
    private static final String COLUMN_DONE = "done";
    private static final String CREATE_TABLE = "CREATE TABLE "+TABLE_NAME+" ("+COLUMN_ID+" INTEGER PRIMARY KEY AUTOINCREMENT,"+COLUMN_DESCRIPTION+" TEXT,"+
    COLUMN_DATE+" DATE,"+COLUMN_DONE+" BOOLEAN)";
    SQLiteDatabase db;

    public DatabaseHelper(Context context)
    {
        super(context,DATABASE_NAME,null,DATABASE_VERSION);
    }


    @Override
    public void onCreate(SQLiteDatabase db)
    {
        this.db = db;
        db.execSQL(CREATE_TABLE);
    }

    @Override
    public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
        String query = "DROP TABLE IF EXISTS "+TABLE_NAME;
        db.execSQL(query);
        this.onCreate(db);
    }

    public  void insertTask(Task task)
    {
        db = getWritableDatabase();
        ContentValues values = new ContentValues();
        values.put(COLUMN_DESCRIPTION,task.getDescription());
        values.put(COLUMN_DATE,task.getDate().toString());
        values.put(COLUMN_DONE,Boolean.FALSE.toString());
        db.insert(TABLE_NAME, null, values);
        db.close();
    }
}

为什么我的日期值在数据库中总是空的？文本字段的输入格式为 MM/dd/yyyy for date.

Answer 1

我遇到过一次这个问题，当时我疯了，我的特殊问题是日期的格式。首先再次检查这一行，并确保它具有获取值：字符串日期 = tfDate.getText().toString();

如果正确，在插入数据库之前将日期格式化为"yyyy-MM-dd"。

类似的东西（内部任务 class）：

public String getDateStr()
{
    SimpleDateFormat dateFormat = new SimpleDateFormat("yyyy-MM-dd");
    String date = dateFormat.format(this.TaskDate);
    return date;
}

Answer 2

我试了很多方法。我试图通过格式化为 yyyy-MM-dd 来插入日期。但是它不能正常工作。

The best way to do it are:

1-将Taskclass的taskDate属性的数据类型转换为String，而数据库中的数据类型为Date。但这是一种推荐的方式。效果很好。

2- 在数据库中将日期存储为 BIGINT。因此，Task class 的属性的数据类型将为 Long。这也是推荐的方式。

I used the first option.

为什么从 Java 添加到 Android 中的 SQLite 数据库的日期值始终为空？

Why date value added from Java to SQLite database in Android is always null?

java

sqlite

android

android-sqlite