在 Android Studio 上使用 Calendar.getInstance() 时如何插入和填充 DateTime

Question

我是 Android 编程的新手。 我的应用有问题，

当我尝试使用Calendar.getInstance() 向数据库中插入一些日期时，我将数据库上的日期列设置为long 并成功添加了日期。但值很奇怪。

当我想在Listview 上显示日期时，我尝试从数据库中选择日期，日期显示奇怪的值，不是像 11-09-2015 等日期格式，而是“2046” ”或“2036”。

我对此完全感到困惑，我在 StackOverflow 上进行了搜索，有一些示例，但它使用 DatePicker，在这里我想我没有使用 DatePicker。

我不知道我到底需要做什么。 请高手帮帮我， 之前谢谢。

注意。这是我的NewTransaction.java 代码（我用来选择日期的活动）：

public class NewTransaction extends ActionBarActivity {
Button btnIDate;
Button btnIAdd;
Button btnICancel;
RadioButton RdIncome;
RadioButton RdOutcome;
EditText txtAmount, txtCashflow, txtType;
DatabaseHelper dbHelper = new DatabaseHelper(this);
SQLiteDatabase db;
MainActivity mainAct = new MainActivity();
int year_x, month_x, day_x;
static final int DIALOG_ID=0;
public static long dateSelected;
public static Integer intAmount = null;
public static String month;
private boolean isUpdateTrans;
private String id, transname, transamount, transtype, transdate, transcategid;

//new trans ad tf salah fi input tgl
@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_new_transaction);
    txtAmount = (EditText)findViewById(R.id.txtAmount);
    txtCashflow = (EditText)findViewById(R.id.txtCashflow);
    txtType = (EditText)findViewById(R.id.txtType);
    RdIncome = (RadioButton)findViewById(R.id.RdBtnIncome);
    RdOutcome = (RadioButton)findViewById(R.id.RdBtnOutcome);

    String catSelected = mainAct.getCatSelected();

    onButtonClickButtonListener(catSelected);
    selectDate();
    showDialogOnClick();
    //kena null object dsni entah knapa
    Bundle bundle= getIntent().getExtras();
    if(bundle!= null) {
        isUpdateTrans = getIntent().getExtras().getBoolean("update");
        if (isUpdateTrans) {
            System.out.print("isUpdate di NewTrans");
            id = getIntent().getExtras().getString("TransId");
            transname = getIntent().getExtras().getString("TransName");
            transamount = getIntent().getExtras().getString("TransAmount");
            transtype = getIntent().getExtras().getString("TransType");
            transdate = getIntent().getExtras().getString("CategDate");
            transcategid = getIntent().getExtras().getString("CategCategId");
            txtCashflow.setText(transname);
            txtType.setText(transtype);
            txtAmount.setText(transamount);
            btnIDate.setText(transdate);

        }
    }
}

private void selectDate(){
    final Calendar cal = Calendar.getInstance();
    year_x = cal.get(Calendar.YEAR);
    month_x = cal.get(Calendar.MONTH);
    day_x = cal.get(Calendar.DAY_OF_MONTH);
    switchMonth(month_x);
    btnIDate = (Button)findViewById(R.id.btnDate);
    btnIDate.setText("Date : " + day_x + "-" + month + "-" + year_x);
    //dateSelected = (year_x+month_x+day_x);
}

public void showDialogOnClick(){
    btnIDate = (Button)findViewById(R.id.btnDate);
    btnIDate.setOnClickListener(
            new View.OnClickListener() {
                @Override
                public void onClick(View v) {
                    showDialog(DIALOG_ID);
                }
            }
    );

}

@Override
protected Dialog onCreateDialog(int id){
    if (id == DIALOG_ID)
            return  new DatePickerDialog(this, dpickerListener , year_x, month_x, day_x);
    return null;

}

private String switchMonth(Integer month_x){
    switch(month_x){
        case 1 : month = "Jan";
            break;
        case 2 : month = "Feb";
            break;
        case 3 : month = "Mar";
            break;
        case 4 : month = "Apr";
            break;
        case 5 : month = "Mei";
            break;
        case 6 : month = "Jun";
            break;
        case 7 : month = "Jul";
            break;
        case 8 : month = "Aug";
            break;
        case 9 : month = "Sep";
            break;
        case 10 : month = "Okt";
            break;
        case 11 : month = "Nov";
            break;
        case 12 : month = "Des";
            break;
    }
    return month;
}

public DatePickerDialog.OnDateSetListener dpickerListener
        = new DatePickerDialog.OnDateSetListener() {
    @Override
    public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
        year_x= year;
        month_x = monthOfYear + 1;
        day_x = dayOfMonth;
        switchMonth(month_x);
        btnIDate = (Button)findViewById(R.id.btnDate);
        btnIDate.setText("Date : " + day_x + "-" + month + "-" + year_x);
        //Toast.makeText(NewTransaction.this, year_x + "/" + month_x + "/" + day_x, Toast.LENGTH_LONG).show();
        dateSelected = view.getCalendarView().getDate();
        Toast.makeText(NewTransaction.this, "Date " + dateSelected, Toast.LENGTH_LONG).show();
        DateFormat.getDateInstance().format(myDatePicker.getCalendarView().getDate());
    }
};

private void clearText(){
    txtCashflow.clearComposingText();
    txtAmount.clearComposingText();
    txtType.clearComposingText();

}

public void onButtonClickButtonListener(final String catSelected){
        btnIAdd = (Button)findViewById(R.id.btnAddTrans);
        btnIAdd.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        if(RdIncome.isChecked()){
                            txtType.setText("Income");
                        }else{
                            txtType.setText("Outcome");
                        }
                        if (isUpdateTrans) {
                            //update
                            Toast.makeText(NewTransaction.this, "Clicked", Toast.LENGTH_LONG).show();
                            intAmount = Integer.parseInt(txtAmount.getText().toString());
                            boolean isInserted = dbHelper.updateTransData(id, txtCashflow.getText().toString(),
                                    intAmount, txtType.getText().toString(), dateSelected, catSelected, null);
                            if (isInserted == true) {
                                Toast.makeText(NewTransaction.this, "Updated", Toast.LENGTH_LONG).show();
                                clearText();
                                Intent intent = new Intent(
                                        NewTransaction.this,
                                        ViewCashflow.class
                                );
                                startActivity(intent);
                            } else
                                Toast.makeText(NewTransaction.this, "Not Inserted", Toast.LENGTH_LONG).show();
                        } else {
                            //insert
                            Toast.makeText(NewTransaction.this, "Clicked", Toast.LENGTH_LONG).show();
                            intAmount = Integer.parseInt(txtAmount.getText().toString());
                            boolean isInserted = dbHelper.insertTransData(txtCashflow.getText().toString(),
                                    intAmount, txtType.getText().toString(), dateSelected, catSelected, null);
                            if (isInserted == true) {
                                Toast.makeText(NewTransaction.this, "Inserted", Toast.LENGTH_LONG).show();
                                clearText();
                                Intent intent = new Intent(
                                        NewTransaction.this,
                                        ViewCashflow.class
                                );
                                startActivity(intent);
                            } else
                                Toast.makeText(NewTransaction.this, "Not Inserted", Toast.LENGTH_LONG).show();
                        }
                    }
                });

        btnICancel = (Button)findViewById(R.id.btnCancelTrans);
        btnICancel.setOnClickListener(
                new View.OnClickListener() {
                    @Override
                    public void onClick(View v) {
                        Intent intent = new Intent(
                                NewTransaction.this,
                                MainActivity.class
                        );
                        startActivity(intent);
                    }
                }
        );
}

@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_new_transaction_, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

Answer 1

使用此函数获取当前日期。它将以dd-MM-yyyy 格式格式化日期。

private static void selectDate() {
        Calendar cal = Calendar.getInstance();
        SimpleDateFormat df = new SimpleDateFormat("dd-MM-yyyy");
        String date = df.format(cal.getTime());
        System.out.println(date);

}

编辑

使用DatePickerDialog

        DatePickerDialog dp = new DatePickerDialog(mContext, new DatePickerDialog.OnDateSetListener() {
            @Override
            public void onDateSet(DatePicker view, int year, int monthOfYear, int dayOfMonth) {
                Log.e("date", year + ":" + monthOfYear + ":" + dayOfMonth);
            }
        }, cal.get(Calendar.YEAR), cal.get(Calendar.MONTH),cal.get(Calendar.DAY_OF_MONTH));

        dp.show();