Add VersatileTextPreference

At the time being, it serves two purposes:

  * It supports changing input type via android:inputType XML
    attribute, which can help the keyboard app with choosing a more
    suitable keyboard layout.

  * If continuousValidator is set, it is used to prevent the user from
    entering invalid data. On each text change, the validator is run;
    if it throws, the Ok button gets disabled.

It was designed as a drop-in replacement of EditTextPreference with the
extra functionality disabled by default. Additional functionality can be
added as needed.

Author: oakkitten

AnkiDroid/src/main/java/com/ichi2/anki/preferences/VersatileTextPreference.kt

@@ -0,0 +1,85 @@
+/*
+ * This program is free software; you can redistribute it and/or modify it under
+ * the terms of the GNU General Public License as published by the Free Software
+ * Foundation; either version 3 of the License, or (at your option) any later
+ * version.
+ *
+ * This program is distributed in the hope that it will be useful, but WITHOUT ANY
+ * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR A
+ * PARTICULAR PURPOSE. See the GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License along with
+ * this program. If not, see <http://www.gnu.org/licenses/>.
+ */
+
+package com.ichi2.anki.preferences
+
+import android.content.Context
+import android.content.DialogInterface
+import android.util.AttributeSet
+import android.view.View
+import android.widget.EditText
+import androidx.appcompat.app.AlertDialog
+import androidx.appcompat.widget.AppCompatEditText
+import androidx.core.widget.addTextChangedListener
+import androidx.preference.EditTextPreference
+import androidx.preference.EditTextPreferenceDialogFragmentCompat
+import kotlin.jvm.Throws
+
+/**
+ * A drop-in alternative to [EditTextPreference] with some extra functionality.
+ *
+ *   * It supports changing input type via `android:inputType` XML attribute,
+ *     which can help the keyboard app with choosing a more suitable keyboard layout.
+ *     For the list of available input types, see [TextView.getInputType].
+ *
+ *   * If [continuousValidator] is set, the dialog uses it to prevent user
+ *     from entering invalid data. On each text change, the validator is run;
+ *     if it throws, the Ok button gets disabled.
+ */
+open class VersatileTextPreference(context: Context, attrs: AttributeSet?) :
+    EditTextPreference(context, attrs), DialogFragmentProvider {
+
+    fun interface Validator {
+        @Throws(Exception::class) fun validate(value: String)
+    }
+
+    val referenceEditText = AppCompatEditText(context, attrs)
+
+    var continuousValidator: Validator? = null
+
+    override fun makeDialogFragment() = VersatileTextPreferenceDialogFragment()
+}
+
+open class VersatileTextPreferenceDialogFragment : EditTextPreferenceDialogFragmentCompat() {
+
+    private val versatileTextPreference get() = preference as VersatileTextPreference
+
+    protected lateinit var editText: EditText
+
+    // This changes input type first, as it resets the cursor,
+    // And only then calls super, which sets up text and moves the cursor to end.
+    //
+    // Positive button isn't present in a dialog until it is shown, which happens around onStart;
+    // for simplicity, obtain it in the listener itself.
+    override fun onBindDialogView(contentView: View) {
+        editText = contentView.findViewById(android.R.id.edit)!!
+        editText.inputType = versatileTextPreference.referenceEditText.inputType
+
+        super.onBindDialogView(contentView)
+
+        versatileTextPreference.continuousValidator?.let { validator ->
+            editText.addTextChangedListener(afterTextChanged = {
+                val alertDialog = dialog as AlertDialog
+                val positiveButton = alertDialog.getButton(DialogInterface.BUTTON_POSITIVE)
+
+                positiveButton?.isEnabled = try {
+                    validator.validate(editText.text.toString())
+                    true
+                } catch (e: Exception) {
+                    false
+                }
+            })
+        }
+    }
+}