[MaterialTimePicker] Pre-fill hour and minute edit texts in text input mode

Resolves #2862

PiperOrigin-RevId: 478507649

Author: paulfthomas

lib/java/com/google/android/material/timepicker/ChipTextInputComboView.java

@@ -106,9 +106,6 @@ public void setChecked(boolean checked) {
     chip.setVisibility(checked ? GONE : VISIBLE);
     if (isChecked()) {
       ViewUtils.requestFocusAndShowKeyboard(editText);
-      if (!TextUtils.isEmpty(editText.getText())) {
-        editText.setSelection(editText.getText().length());
-      }
     }
   }
 
@@ -118,10 +115,11 @@ public void toggle() {
   }
 
   public void setText(CharSequence text) {
-    chip.setText(formatText(text));
-    if (!TextUtils.isEmpty(editText.getText())) {
+    String formattedText = formatText(text);
+    chip.setText(formattedText);
+    if (!TextUtils.isEmpty(formattedText)) {
       editText.removeTextChangedListener(watcher);
-      editText.setText(null);
+      editText.setText(formattedText);
       editText.addTextChangedListener(watcher);
     }
   }

lib/java/com/google/android/material/timepicker/TimePickerTextInputKeyController.java

@@ -112,6 +112,8 @@ private boolean onMinuteKeyPress(int keyCode, KeyEvent event, EditText editText)
       return true;
     }
 
+    clearPrefilledText(editText);
+
     return false;
   }
 
@@ -133,6 +135,15 @@ private boolean onHourKeyPress(int keyCode, KeyEvent event, EditText editText) {
       return true;
     }
 
+    clearPrefilledText(editText);
+
     return false;
   }
+
+  // Improve UX by auto-clearing existing text when entering new time
+  private void clearPrefilledText(EditText editText) {
+    if (editText.getSelectionStart() == 0 && editText.length() == 2) {
+      editText.getText().clear();
+    }
+  }
 }

lib/javatests/com/google/android/material/timepicker/TimePickerTextInputKeyControllerTest.java

@@ -77,6 +77,50 @@ public void controller_pressingBackSpace_switchesToHour() {
     assertThat(timeModel.selection).isEqualTo(HOUR);
   }
 
+  @Test
+  public void controller_clearPrefilledText_shouldClearWhenSelection0() {
+    EditText editText = hourInput.getTextInput().getEditText();
+    editText.setText("00");
+    editText.setSelection(0);
+    pressKeys(editText, KeyEvent.KEYCODE_0);
+    shadowOf(getMainLooper()).idle();
+
+    assertThat(editText.getText().length()).isEqualTo(0);
+  }
+
+  @Test
+  public void controller_clearPrefilledText_shouldNotClearWhenSelection1() {
+    EditText editText = hourInput.getTextInput().getEditText();
+    editText.setText("00");
+    editText.setSelection(1);
+    pressKeys(editText, KeyEvent.KEYCODE_0);
+    shadowOf(getMainLooper()).idle();
+
+    assertThat(editText.getText().length()).isEqualTo(2);
+  }
+
+  @Test
+  public void controller_clearPrefilledText_shouldNotClearWhenSelection2() {
+    EditText editText = hourInput.getTextInput().getEditText();
+    editText.setText("00");
+    editText.setSelection(2);
+    pressKeys(editText, KeyEvent.KEYCODE_0);
+    shadowOf(getMainLooper()).idle();
+
+    assertThat(editText.getText().length()).isEqualTo(2);
+  }
+
+  @Test
+  public void controller_clearPrefilledText_shouldNotClearWhenPartialText() {
+    EditText editText = hourInput.getTextInput().getEditText();
+    editText.setText("0");
+    editText.setSelection(0);
+    pressKeys(editText, KeyEvent.KEYCODE_0);
+    shadowOf(getMainLooper()).idle();
+
+    assertThat(editText.getText().length()).isEqualTo(1);
+  }
+
   private static void pressKeys(EditText editText, int... keycodes) {
     for (int key : keycodes) {
       editText.dispatchKeyEvent(new KeyEvent(0, 0, KeyEvent.ACTION_DOWN, key, 0));