Separate date format string from date hint string in MaterialDatePicker for better hints.

Resolves #695

PiperOrigin-RevId: 279095896
(cherry picked from commit c097d3d)

Author: ldjcmu

lib/java/com/google/android/material/datepicker/DateFormatTextWatcher.java

@@ -29,24 +29,21 @@
 
 abstract class DateFormatTextWatcher implements TextWatcher {
 
-  private final String pattern;
+  private final String formatHint;
   private final DateFormat dateFormat;
   @NonNull private final TextInputLayout textInputLayout;
   private final CalendarConstraints constraints;
-  private final String invalidFormat;
   private final String outOfRange;
 
   DateFormatTextWatcher(
-      String pattern,
+      String formatHint,
       DateFormat dateFormat,
       @NonNull TextInputLayout textInputLayout,
       CalendarConstraints constraints) {
-    this.pattern = pattern;
+    this.formatHint = formatHint;
     this.dateFormat = dateFormat;
     this.textInputLayout = textInputLayout;
     this.constraints = constraints;
-    this.invalidFormat =
-        textInputLayout.getContext().getString(R.string.mtrl_picker_invalid_format);
     this.outOfRange = textInputLayout.getContext().getString(R.string.mtrl_picker_out_of_range);
   }
 
@@ -79,7 +76,17 @@ public void onTextChanged(@NonNull CharSequence s, int start, int before, int co
         onInvalidDate();
       }
     } catch (ParseException e) {
-      textInputLayout.setError(String.format(invalidFormat, pattern));
+      String invalidFormat =
+          textInputLayout.getContext().getString(R.string.mtrl_picker_invalid_format);
+      String useLine =
+          String.format(
+              textInputLayout.getContext().getString(R.string.mtrl_picker_invalid_format_use),
+              formatHint);
+      String exampleLine =
+          String.format(
+              textInputLayout.getContext().getString(R.string.mtrl_picker_invalid_format_example),
+              dateFormat.format(new Date(UtcDates.getTodayCalendar().getTimeInMillis())));
+      textInputLayout.setError(invalidFormat + "\n" + useLine + "\n" + exampleLine);
       onInvalidDate();
     }
   }

lib/java/com/google/android/material/datepicker/RangeDateSelector.java

@@ -179,11 +179,9 @@ public View onCreateTextInputView(
     EditText startEditText = startTextInput.getEditText();
     EditText endEditText = endTextInput.getEditText();
 
-    String pattern = root.getResources().getString(R.string.mtrl_picker_text_input_date_format);
     invalidRangeStartError = root.getResources().getString(R.string.mtrl_picker_invalid_range);
 
-    SimpleDateFormat format = UtcDates.getSimpleFormat(pattern);
-    format.setLenient(false);
+    SimpleDateFormat format = UtcDates.getTextInputFormat();
 
     if (selectedStartItem != null) {
       startEditText.setText(format.format(selectedStartItem));
@@ -194,8 +192,10 @@ public View onCreateTextInputView(
       proposedTextEnd = selectedEndItem;
     }
 
+    String formatHint = UtcDates.getTextInputHint(root.getResources(), format);
+
     startEditText.addTextChangedListener(
-        new DateFormatTextWatcher(pattern, format, startTextInput, constraints) {
+        new DateFormatTextWatcher(formatHint, format, startTextInput, constraints) {
 
           @Override
           void onValidDate(@Nullable Long day) {
@@ -211,7 +211,7 @@ void onInvalidDate() {
         });
 
     endEditText.addTextChangedListener(
-        new DateFormatTextWatcher(pattern, format, endTextInput, constraints) {
+        new DateFormatTextWatcher(formatHint, format, endTextInput, constraints) {
           void onValidDate(@Nullable Long day) {
             proposedTextEnd = day;
             updateIfValidTextProposal(startTextInput, endTextInput, listener);

lib/java/com/google/android/material/datepicker/SingleDateSelector.java

@@ -100,17 +100,15 @@ public View onCreateTextInputView(
 
     TextInputLayout dateTextInput = root.findViewById(R.id.mtrl_picker_text_input_date);
     EditText dateEditText = dateTextInput.getEditText();
-
-    String pattern = root.getResources().getString(R.string.mtrl_picker_text_input_date_format);
-    SimpleDateFormat format = UtcDates.getSimpleFormat(pattern);
-    format.setLenient(false);
+    SimpleDateFormat format = UtcDates.getTextInputFormat();
+    String formatHint = UtcDates.getTextInputHint(root.getResources(), format);
 
     if (selectedItem != null) {
       dateEditText.setText(format.format(selectedItem));
     }
 
     dateEditText.addTextChangedListener(
-        new DateFormatTextWatcher(pattern, format, dateTextInput, constraints) {
+        new DateFormatTextWatcher(formatHint, format, dateTextInput, constraints) {
 
           @Override
           void onValidDate(@Nullable Long day) {

lib/java/com/google/android/material/datepicker/UtcDates.java

@@ -15,7 +15,10 @@
  */
 package com.google.android.material.datepicker;
 
+import com.google.android.material.R;
+
 import android.annotation.TargetApi;
+import android.content.res.Resources;
 import android.os.Build.VERSION_CODES;
 import androidx.annotation.NonNull;
 import java.text.DateFormat;
@@ -90,6 +93,26 @@ private static DateFormat getFormat(int style, Locale locale) {
     return format;
   }
 
+  static SimpleDateFormat getTextInputFormat() {
+    String pattern =
+        ((SimpleDateFormat) DateFormat.getDateInstance(DateFormat.SHORT, Locale.getDefault()))
+            .toLocalizedPattern()
+            .replaceAll("\\s+", "");
+    SimpleDateFormat format = new SimpleDateFormat(pattern, Locale.getDefault());
+    format.setTimeZone(UtcDates.getTimeZone());
+    format.setLenient(false);
+    return format;
+  }
+
+  static String getTextInputHint(Resources res, SimpleDateFormat format) {
+    String formatHint = format.toLocalizedPattern();
+    String yearChar = res.getString(R.string.mtrl_picker_text_input_year_abbr);
+    String monthChar = res.getString(R.string.mtrl_picker_text_input_month_abbr);
+    String dayChar = res.getString(R.string.mtrl_picker_text_input_day_abbr);
+
+    return formatHint.replaceAll("d", dayChar).replaceAll("M", monthChar).replaceAll("y", yearChar);
+  }
+
   static SimpleDateFormat getSimpleFormat(String pattern) {
     return getSimpleFormat(pattern, Locale.getDefault());
   }

lib/java/com/google/android/material/datepicker/res/values/strings.xml

@@ -29,13 +29,16 @@
   <string name="mtrl_picker_text_input_date_range_start_hint" description="Label for the start date in a range selected by the user [CHAR_LIMIT=60]">Start date</string>
   <string name="mtrl_picker_text_input_date_range_end_hint" description="Label for the end date in a range selected by the user [CHAR_LIMIT=60]">End date</string>
   <!-- TODO(b/134174653): internationalize date format strings -->
-  <string name="mtrl_picker_date_format" description="The format for how a date will be shown to the user, with the year included [CHAR_LIMIT=16]">MMM dd, yyyy</string>
-  <string name="mtrl_picker_date_format_without_year" description="The format for how a date will be shown to the user, without the year included [CHAR_LIMIT=16]">MMM dd</string>
-  <string name="mtrl_picker_text_input_date_format" description="The format for how the user should enter a date via text input [CHAR_LIMIT=16]">MM/dd/yyyy</string>
+  <string name="mtrl_picker_text_input_year_abbr" description="A 1 character abbreviation for year. It will be part of a string such as dd/mm/yyyy or mm/dd/yyyy or y.mm.dd. [CHAR_LIMIT=1]">y</string>
+  <string name="mtrl_picker_text_input_month_abbr" description="A 1 character abbreviation for month. It will be part of a string such as dd/mm/yyyy or mm/dd/yyyy or y.mm.dd. [CHAR_LIMIT=1]">m</string>
+  <string name="mtrl_picker_text_input_day_abbr" description="A 1 character abbreviation for day. It will be part of a string such as dd/mm/yyyy or mm/dd/yyyy or y.mm.dd. [CHAR_LIMIT=1]">d</string>
   <string name="mtrl_picker_save" description="Confirms the selection [CHAR_LIMIT=12]">Save</string>
   <string name="mtrl_picker_invalid_range" description="Notifies the user that the two entered dates do not represent a valid range of dates [CHAR_LIMIT=36]">Invalid range.</string>
   <string name="mtrl_picker_out_of_range" description="Notifies the user that the entered date is outside the allowed range [CHAR_LIMIT=36]">Out of range: %1$s</string>
-  <string name="mtrl_picker_invalid_format" description="Indicates that the user entered date cannot be parsed because its format is wrong. The user should instead use the format after the colon. Includes a line break [CHAR_LIMIT=54]">Invalid format.\nUse: %1$s</string>
+
+  <string name="mtrl_picker_invalid_format" description="Indicates that the user entered date cannot be parsed because its format is wrong. [CHAR_LIMIT=36]">Invalid format.</string>
+  <string name="mtrl_picker_invalid_format_use" description="Tells a user what format is expected for their date entry. [CHAR_LIMIT=18]">Use: %1$s</string>
+  <string name="mtrl_picker_invalid_format_example" description="Tells a user what an example valid entry looks like. [CHAR_LIMIT=18]">Example: %1$s</string>
 
   <string name="mtrl_picker_toggle_to_calendar_input_mode" description="a11y string to indicate this button changes the input mode to a calendar [CHAR_LIMIT=NONE]">Switch to calendar input mode</string>
   <string name="mtrl_picker_toggle_to_text_input_mode" description="a11y string to indicate this button changes the input mode to a text field [CHAR_LIMIT=NONE]">Switch to text input mode</string>