Angular Material - Long Textarea Forces Scroll To Top

The issue of the scroll bar jumping to the top when dealing with long text in a textarea is a common problem. This issue is caused by the default behavior of Angular Material's textarea element, where the scrollbar is positioned at the top when the textarea's content overflows.

To prevent the scroll bar from jumping to the top when editing long text in a textarea, you can use the cdkTextareaAutosize directive from Angular's CDK (Component Dev Kit). This directive automatically adjusts the height of the textarea to fit its content and prevents the scroll bar from jumping to the top.

Here's how you can use the cdkTextareaAutosize directive with Angular Material:

1. Install Angular CDK: If you haven't already, install Angular CDK by running the following command:

   bashCopy code
   npm install @angular/cdk
   

2. Import and Add cdkTextareaAutosize Directive: In your Angular component that uses the textarea, import the cdkTextareaAutosize directive and add it to the textarea element.

   htmlCopy code
   <!-- component.html -->
   <mat-form-field>
     <textarea matInput
               cdkTextareaAutosize
               cdkAutosizeMinRows="2"
               cdkAutosizeMaxRows="5"
               [(ngModel)]="longText">
     </textarea>
   </mat-form-field>
   

   In this example, we use cdkAutosizeMinRows and cdkAutosizeMaxRows to set the minimum and maximum number of rows for the textarea. You can adjust these values as per your requirements.

3. Import and Add cdkTextareaAutosize Module: In your app module or a shared module, import and add the CdkTextareaAutosizeModule to the imports array.

   typescriptCopy code
   // app.module.ts or shared.module.ts
   import { NgModule } from '@angular/core';
   import { BrowserModule } from '@angular/platform-browser';
   import { BrowserAnimationsModule } from '@angular/platform-browser/animations';
   import { CdkTextareaAutosizeModule } from '@angular/cdk/text-field';
   
   @NgModule({
     imports: [
       BrowserModule,
       BrowserAnimationsModule,
       CdkTextareaAutosizeModule
     ],
     // Other declarations, providers, etc.
   })
   export class AppModule { }
   

4. Styling (Optional): Depending on your CSS styles and the surrounding layout, you may need to adjust the styles for the mat-form-field and the textarea. By default, Angular Material applies some styles, but you may want to customize it to fit your design.

With the cdkTextareaAutosize directive, the textarea's height will now adjust automatically as you type and prevent the scrollbar from jumping to the top. It provides a smooth user experience when editing long text in the textarea without the scrollbar interrupting the editing process.