Added info and a sample of custom invalidation in input dialogs.

README.md

@@ -804,8 +804,12 @@ take the second error color parameter*
 
 The easiest way to invalidate (enable or disable the EditText based on whether you think the input is acceptable)
 input dialogs is to call `alwaysCallInputCallback()` from the `Builder` so that the callback is invoked
-every time the user changes their input. From there, you can constantly check what they've typed
-and use `setEnabled()` on the `EditText` view (which can be retrieved with `MaterialDialog#getInputEditText()`).
+every time the user changes their input. From there, you can constantly check what they've typed. If you
+decide they shouldn't be able to submit that, you can disable the submit button using this from within the callback:
+
+```java
+dialog.getActionButton(DialogAction.POSITIVE).setEnabled(false);
+```
 
 ---
 

sample/src/main/java/com/afollestad/materialdialogssample/MainActivity.java

@@ -220,6 +220,13 @@ public class MainActivity extends AppCompatActivity implements
             }
         });
 
+        findViewById(R.id.input_custominvalidation).setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                showInputDialogCustomInvalidation();
+            }
+        });
+
         findViewById(R.id.progress1).setOnClickListener(new View.OnClickListener() {
             @Override
             public void onClick(View v) {
@@ -635,6 +642,29 @@ public class MainActivity extends AppCompatActivity implements
                 }).show();
     }
 
+    private void showInputDialogCustomInvalidation() {
+        new MaterialDialog.Builder(this)
+                .title(R.string.input)
+                .content(R.string.input_content_custominvalidation)
+                .inputType(InputType.TYPE_CLASS_TEXT |
+                        InputType.TYPE_TEXT_VARIATION_PERSON_NAME |
+                        InputType.TYPE_TEXT_FLAG_CAP_WORDS)
+                .positiveText(R.string.submit)
+                .alwaysCallInputCallback() // this forces the callback to be invoked with every input change
+                .input(R.string.input_hint, 0, false, new MaterialDialog.InputCallback() {
+                    @Override
+                    public void onInput(MaterialDialog dialog, CharSequence input) {
+                        if (input.toString().equalsIgnoreCase("hello")) {
+                            dialog.setContent("I told you not to type that!");
+                            dialog.getActionButton(DialogAction.POSITIVE).setEnabled(false);
+                        } else {
+                            dialog.setContent(R.string.input_content_custominvalidation);
+                            dialog.getActionButton(DialogAction.POSITIVE).setEnabled(true);
+                        }
+                    }
+                }).show();
+    }
+
     private void showProgressDialog(boolean indeterminate, boolean horizontalIndeterminate) {
         if (indeterminate) {
             new MaterialDialog.Builder(this)

sample/src/main/res/layout/activity_main.xml

@@ -163,6 +163,13 @@
             android:layout_marginTop="@dimen/sample_button_spacing"
             android:text="@string/input" />
 
+        <Button
+            android:id="@+id/input_custominvalidation"
+            android:layout_width="match_parent"
+            android:layout_height="56dp"
+            android:layout_marginTop="@dimen/sample_button_spacing"
+            android:text="@string/input_custominvalidation" />
+
         <Button
             android:id="@+id/progress1"
             android:layout_width="match_parent"

sample/src/main/res/values/strings.xml

@@ -150,6 +150,7 @@
     <!-- Optional button to Skip a PreferenceActivity [CHAR LIMIT=20] -->
     <string name="skip_button_label">Skip</string>
     <string name="input">Input</string>
+    <string name="input_custominvalidation">Input (Custom Invalidation)</string>
     <string name="input_hint">John Appleseed</string>
     <string name="input_content">What\'s your name?</string>
     <string name="simple_list">Simple Dialog (Guidelines Spec)</string>
@@ -160,5 +161,6 @@
     <string name="preference_dialog_title">Dialog Title</string>
     <string name="material_dialog_pref_title">Dialog Preference</string>
     <string name="material_dialog_pref_summary">This is an example of a basic dialog preference that automatically uses Material Dialogs to show the dialog.</string>
+    <string name="input_content_custominvalidation">Do not type hello, or else!</string>
 
 </resources>