Android:DatePicker textview DMY格式并希望将其保存为YMD格式

我有一个可点击的文本视图，并且有一个日期选择器对话框。然后，日期选择器将textview中的日期设置为日、月、年格式。 我想以年、月、日的格式存储它。 我希望它在textview中显示为DMY，但在SQLITE中它必须存储为YDM。 我使用了下面的方法，但它给了我非法的例外

private void updateDisplay() {
    date.setText(new StringBuilder()
            .append(mDay).append("-")
            .append(mMonth + 1).append("-")
            .append(mYear));   
String datepicker = date_tv.getText().toString();
SimpleDateFormat sdf= new SimpleDateFormat("yyyy-MM-dd", java.util.Locale.getDefault());
datepicker = sdf.format(date_tv);
cv = new ContentValues();
cv.put(DBAdapter.COLUMN_METER_DATE, datepicker);

它给了我以下的错误

02-26 08:42:07.114: E/AndroidRuntime(5109): FATAL EXCEPTION: main
02-26 08:42:07.114: E/AndroidRuntime(5109): Process: com.example.mscprojectimagebuttons, PID: 5109
02-26 08:42:07.114: E/AndroidRuntime(5109): java.lang.IllegalArgumentException: Bad class: class android.widget.TextView
02-26 08:42:07.114: E/AndroidRuntime(5109):     at java.text.DateFormat.format(DateFormat.java:296)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at java.text.Format.format(Format.java:93)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at com.example.mscprojectimagebuttons.MeterFragment$2.onClick(MeterFragment.java:98)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at android.view.View.performClick(View.java:4438)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at android.view.View$PerformClick.run(View.java:18422)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at android.os.Handler.handleCallback(Handler.java:733)
 02-26 08:42:07.114: E/AndroidRuntime(5109):    at android.os.Handler.dispatchMessage(Handler.java:95)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at android.os.Looper.loop(Looper.java:136)
 02-26 08:42:07.114: E/AndroidRuntime(5109):    at android.app.ActivityThread.main(ActivityThread.java:5017)
02-26 08:42:07.114: E/AndroidRuntime(5109):     at java.lang.reflect.Method.invokeNative(Native Method)
 02-26 08:42:07.114: E/AndroidRuntime(5109):    at java.lang.reflect.Method.invoke(Method.java:515)
 02-26 08:42:07.114: E/AndroidRuntime(5109):    at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:779)
 02-26 08:42:07.114: E/AndroidRuntime(5109):    at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:595)
 02-26 08:42:07.114: E/AndroidRuntime(5109):    at dalvik.system.NativeStart.main(Native Method)

替换

datepicker = sdf.format(date_tv);

借

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还是有同样的问题。尝试此操作后出现相同错误

datepicker = sdf.format(datepicker);