File question in composite component doesn't show files in preview mo…

src/question_file.ts

@@ -921,9 +921,8 @@ export class QuestionFileModel extends QuestionFileModelBase {
     super.updateElementCss(reNew);
     this.updateCurrentMode();
   }
-
-  endLoadingFromJson(): void {
-    super.endLoadingFromJson();
+  public onSurveyLoad(): void {
+    super.onSurveyLoad();
     this.updateCurrentMode();
     this.updateActionsVisibility();
     this.loadPreview(this.value);

tests/questionFileTests.ts

@@ -1129,7 +1129,7 @@ QUnit.test("QuestionFile remove file by preview value", function (assert) {
   });
 });
 
-QUnit.test("QuestionFile download file content on preview", function (assert) {
+QUnit.test("QuestionFile download file content on preview, #1", function (assert) {
   var json = {
     showPreviewBeforeComplete: "showAnsweredQuestions",
     elements: [
@@ -1386,7 +1386,7 @@ QUnit.test("Check file question processResponsiveness method", (assert) => {
   assert.equal(question.pageSize, 4);
 });
 
-QUnit.test("QuestionFile download file content on preview", function (assert) {
+QUnit.test("QuestionFile download file content on preview, #2", function (assert) {
   const survey = new SurveyModel({
     elements: [
       { type: "file", name: "q1" },

tests/question_customtests.ts

@@ -16,6 +16,7 @@ import { LocalizableString } from "../src/localizablestring";
 import { PanelModel } from "../src/panel";
 import { StylesManager } from "../src/stylesmanager";
 import { ArrayChanges, Base } from "../src/base";
+import { QuestionFileModel } from "../src/question_file";
 
 export default QUnit.module("custom questions");
 
@@ -2891,3 +2892,54 @@ QUnit.test("Bug with visibleIf with composite.question and panel dynamic. Bug#77
   assert.equal(q2.isVisible, true, "isVisible #3");
   ComponentCollection.Instance.clear();
 });
+QUnit.test("file question in composite component doesn't show preview in preview mode. Bug#7826", function (assert) {
+  ComponentCollection.Instance.add({
+    name: "test",
+    elementsJSON: [
+      {
+        type: "file",
+        name: "file_q",
+        allowMultiple: true,
+        storeDataAsText: false
+      },
+    ]
+  });
+
+  const survey = new SurveyModel({
+    elements: [
+      { type: "test", name: "q1" },
+      { type: "file", name: "q2", storeDataAsText: false }
+    ]
+  });
+  survey.onUploadFiles.add((survey, options) => {
+    options.callback(
+      "success",
+      options.files.map((file) => {
+        return { file: file, content: file.name + "_url" };
+      })
+    );
+  });
+
+  const compQuestion = <QuestionCompositeModel>survey.getQuestionByName("q1");
+  const file_q1 = <QuestionFileModel>compQuestion.contentPanel.getQuestionByName("file_q");
+  const file_q2 = <QuestionFileModel>survey.getQuestionByName("q2");
+  file_q1.loadFiles([{ name: "f1", type: "t1" } as any]);
+  file_q2.loadFiles([{ name: "f1", type: "t1" } as any]);
+  assert.equal(file_q1.showPreviewContainer, true, "file_q1 #1");
+  assert.equal(file_q2.showPreviewContainer, true, "file_q2 #1");
+
+  survey.showPreview();
+  assert.equal(survey.state, "preview", "state #1");
+  const compQuestion_preview = <QuestionCompositeModel>survey.getQuestionByName("q1");
+  const file_q1_preview = <QuestionFileModel>compQuestion_preview.contentPanel.getQuestionByName("file_q");
+  const file_q2_preview = <QuestionFileModel>survey.getQuestionByName("q2");
+  assert.equal(file_q1_preview.showPreviewContainer, true, "file_q1_preview #1");
+  assert.equal(file_q2_preview.showPreviewContainer, true, "file_q2_preview #1");
+
+  survey.cancelPreview();
+  assert.equal(survey.state, "running", "state #2");
+  assert.equal(file_q1.showPreviewContainer, true, "file_q1 #1");
+  assert.equal(file_q2.showPreviewContainer, true, "file_q2 #1");
+
+  ComponentCollection.Instance.clear();
+});