[[dynamically-injecting-css]] Dynamically injecting CSS ------------------------- In most cases you will style your components using SASS or CSS and create a theme for the application which you include with the `@Theme` annotation. This is always the preferred way of theming your application. But in some cases this is not enough. Sometimes you will want your user to be able to change some property on-the-fly without providing pre-made class names. To do this you can use CSS style injection. In this example I am going to show you how you can use CSS injection to create an editor which you can use to modify text visually with, a WYSIWYG of sorts. Here is an image of the final component I am going to create: image:img/theme-editor.png[Theme editor] First lets start by defining the UI of the editor component, it looks like this: [source,java] .... private Component createEditor(String text) { Panel editor = new Panel("Text Editor"); editor.setWidth("580px"); VerticalLayout panelContent = new VerticalLayout(); panelContent.setSpacing(true); panelContent.setMargin(new MarginInfo(true, false, false, false)); editor.setContent(panelContent); // Create the toolbar HorizontalLayout toolbar = new HorizontalLayout(); toolbar.setSpacing(true); toolbar.setMargin(new MarginInfo(false, false, false, true)); // Create the font family selector toolbar.addComponent(createFontSelect()); // Create the font size selector toolbar.addComponent(createFontSizeSelect()); // Create the text color selector toolbar.addComponent(createTextColorSelect()); // Create the background color selector toolbar.addComponent(createBackgroundColorSelect()); panelContent.addComponent(toolbar); panelContent.setComponentAlignment(toolbar, Alignment.MIDDLE_LEFT); // Spacer between toolbar and text panelContent.addComponent(new Label("

", ContentMode.HTML)); // The text to edit TextArea textLabel = new TextArea(null, text); textLabel.setWidth("100%"); textLabel.setHeight("200px"); // IMPORTANT: We are here setting the style name of the label, we are going to use this in our injected styles to target the label textLabel.setStyleName("text-label"); panelContent.addComponent(textLabel); return editor; } .... Basically the editor component is a Panel with a text area and some buttons which you can use to modify the text area text with. The important thing here is that we give the text area a style name "text-label". With this style name we will be able to inject CSS styles targeted at that text area and modify colors and fonts of it. Lets next take a look at how the controls in the toolbar is implemented. They are all pretty similar but lets first take a look at how the Font selector was made: [source,java] .... private Component createFontSelect() { final ComboBox select = new ComboBox(null, Arrays.asList("Arial", "Helvetica", "Verdana", "Courier", "Times", "sans-serif")); select.setValue("Arial"); select.setWidth("200px"); select.setInputPrompt("Font"); select.setDescription("Font"); select.setImmediate(true); select.setNullSelectionAllowed(false); select.setNewItemsAllowed(false); select.addValueChangeListener(new ValueChangeListener() { @Override public void valueChange( ValueChangeEvent event ) { // Get the new font family String fontFamily = select.getValue().toString(); // Get the stylesheet of the page Styles styles = Page.getCurrent().getStyles(); // inject the new font size as a style. We need .v-app to override Vaadin's default styles here styles.add(".v-app .v-textarea.text-label { font-family:" + fontFamily + "; }"); } }); return select; } .... The important part here is what is inside the `ValueChangeListener`. Once we get the value from the ComboBox we are ready to inject it to the page so the user can visually see what have changed. To do this we fetch the StyleSheet for the current Page by calling `Page.getCurrent()`. Once we have the current Page we can get its StyleSheet by calling `Page.getstyleSheet()`. Once we got the StyleSheet we are free to inject any CSS string into the page by using `StyleSheet.inject(String css)`. As you see here we use the style name we gave to the TextArea as the selector and apply the font-family attribute to change the font family to the one the user has selected. For the sake of clarity, lets look at how another one, the text color selector, was implemented: [source,java] .... private Component createTextColorSelect( ) { // Colorpicker for changing text color ColorPicker textColor = new ColorPicker("Color", Color.BLACK); textColor.setWidth("110px"); textColor.setCaption("Color"); textColor.addColorChangeListener(new ColorChangeListener() { @Override public void colorChanged( ColorChangeEvent event ) { // Get the new text color Color color = event.getColor(); // Get the stylesheet of the page Styles styles = Page.getCurrent().getStyles(); // inject the new color as a style styles.add(".v-app .v-textarea.text-label { color:" + color.getCSS() + "; }"); } }); return textColor; } .... Again, the important part in this method is in the `ColorChangeListener`. Basically here we do the exactly same thing as we did with the font family except here we are dealing with a color. To change the color of the text we just simply apply the 'color' attribute for text area. The `ColorPicker.Color` even provides us with a convenient method of directly converting the received Color object into a CSS color. And finally, for completeness, here is the full example code which will produce the demo application in the picture above for you to try out: [source,java] .... /** * Imports and package definition omitted */ public class CSSInjectWithColorpicker extends UI { @Override protected void init( VaadinRequest request ) { // Create a text editor Component editor = createEditor("Lorem ipsum dolor sit amet, lacus pharetra sed, sit a " + "tortor. Id aliquam lorem pede, orci ut enim metus, diam nulla mi " + "suspendisse tempor tortor. Eleifend lorem proin, morbi vel diam ut. " + "Tempor est tellus vitae, pretium condimentum facilisis sit. Sagittis " + "quam, ac urna eros est cras id cras, eleifend eu mattis nec." + "Lorem ipsum dolor sit amet, lacus pharetra sed, sit a " + "tortor. Id aliquam lorem pede, orci ut enim metus, diam nulla mi " + "suspendisse tempor tortor. Eleifend lorem proin, morbi vel diam ut. " + "Tempor est tellus vitae, pretium condimentum facilisis sit. Sagittis " + "quam, ac urna eros est cras id cras, eleifend eu mattis nec." + "Lorem ipsum dolor sit amet, lacus pharetra sed, sit a " + "tortor. Id aliquam lorem pede, orci ut enim metus, diam nulla mi " + "suspendisse tempor tortor. Eleifend lorem proin, morbi vel diam ut. " + "Tempor est tellus vitae, pretium condimentum facilisis sit. Sagittis " + "quam, ac urna eros est cras id cras, eleifend eu mattis nec." + "Lorem ipsum dolor sit amet, lacus pharetra sed, sit a " + "tortor. Id aliquam lorem pede, orci ut enim metus, diam nulla mi " + "suspendisse tempor tortor. Eleifend lorem proin, morbi vel diam ut. " + "Tempor est tellus vitae, pretium condimentum facilisis sit. Sagittis " + "quam, ac urna eros est cras id cras, eleifend eu mattis nec."); VerticalLayout content = new VerticalLayout(editor); content.setMargin(true); setContent(content); } /** * Creates a text editor for visually editing text * * @param text The text editor * @return */ private Component createEditor( String text ) { Panel editor = new Panel("Text Editor"); editor.setWidth("580px"); VerticalLayout panelContent = new VerticalLayout(); panelContent.setSpacing(true); panelContent.setMargin(new MarginInfo(true, false, false, false)); editor.setContent(panelContent); // Create the toolbar HorizontalLayout toolbar = new HorizontalLayout(); toolbar.setSpacing(true); toolbar.setMargin(new MarginInfo(false, false, false, true)); // Create the font family selector toolbar.addComponent(createFontSelect()); // Create the font size selector toolbar.addComponent(createFontSizeSelect()); // Create the text color selector toolbar.addComponent(createTextColorSelect()); // Create the background color selector toolbar.addComponent(createBackgroundColorSelect()); panelContent.addComponent(toolbar); panelContent.setComponentAlignment(toolbar, Alignment.MIDDLE_LEFT); // Spacer between toolbar and text panelContent.addComponent(new Label("

", ContentMode.HTML)); // The text to edit TextArea textLabel = new TextArea(null, text); textLabel.setWidth("100%"); textLabel.setHeight("200px"); // IMPORTANT: We are here setting the style name of the label, we are going to use this in our injected styles to // target the label textLabel.setStyleName("text-label"); panelContent.addComponent(textLabel); return editor; } /** * Creates a background color select dialog */ private Component createBackgroundColorSelect( ) { ColorPicker bgColor = new ColorPicker("Background", Color.WHITE); bgColor.setWidth("110px"); bgColor.setCaption("Background"); bgColor.addColorChangeListener(new ColorChangeListener() { @Override public void colorChanged( ColorChangeEvent event ) { // Get the new background color Color color = event.getColor(); // Get the stylesheet of the page Styles styles = Page.getCurrent().getStyles(); // inject the new background color styles.add(".v-app .v-textarea.text-label { background-color:" + color.getCSS() + "; }"); } }); return bgColor; } /** * Create a text color selection dialog */ private Component createTextColorSelect( ) { // Colorpicker for changing text color ColorPicker textColor = new ColorPicker("Color", Color.BLACK); textColor.setWidth("110px"); textColor.setCaption("Color"); textColor.addColorChangeListener(new ColorChangeListener() { @Override public void colorChanged( ColorChangeEvent event ) { // Get the new text color Color color = event.getColor(); // Get the stylesheet of the page Styles styles = Page.getCurrent().getStyles(); // inject the new color as a style styles.add(".v-app .v-textarea.text-label { color:" + color.getCSS() + "; }"); } }); return textColor; } /** * Creates a font family selection dialog */ private Component createFontSelect( ) { final ComboBox select = new ComboBox(null, Arrays.asList("Arial", "Helvetica", "Verdana", "Courier", "Times", "sans-serif")); select.setValue("Arial"); select.setWidth("200px"); select.setInputPrompt("Font"); select.setDescription("Font"); select.setImmediate(true); select.setNullSelectionAllowed(false); select.setNewItemsAllowed(false); select.addValueChangeListener(new ValueChangeListener() { @Override public void valueChange( ValueChangeEvent event ) { // Get the new font family String fontFamily = select.getValue().toString(); // Get the stylesheet of the page Styles styles = Page.getCurrent().getStyles(); // inject the new font size as a style. We need .v-app to override Vaadin's default styles here styles.add(".v-app .v-textarea.text-label { font-family:" + fontFamily + "; }"); } }); return select; } /** * Creates a font size selection control */ private Component createFontSizeSelect( ) { final ComboBox select = new ComboBox(null, Arrays.asList(8, 9, 10, 12, 14, 16, 20, 25, 30, 40, 50)); select.setWidth("100px"); select.setValue(12); select.setInputPrompt("Font size"); select.setDescription("Font size"); select.setImmediate(true); select.setNullSelectionAllowed(false); select.setNewItemsAllowed(false); select.addValueChangeListener(new ValueChangeListener() { @Override public void valueChange( ValueChangeEvent event ) { // Get the new font size Integer fontSize = (Integer) select.getValue(); // Get the stylesheet of the page Styles styles = Page.getCurrent().getStyles(); // inject the new font size as a style. We need .v-app to override Vaadin's default styles here styles.add(".v-app .v-textarea.text-label { font-size:" + String.valueOf(fontSize) + "px; }"); } }); return select; } } .... ref='#n257'>257 258 259 260 261 262 263 264 265 266 267 268 269 270 271 272 273 274 275 276 277 278 279 280 281 282 283 284 285 286 287 288 289 290 291 292 293 294 295 296 297 298 299 300 301 302 303 304 305 306 307 308 309 310 311 312 313 314 315 316 317 318 319 320 321 322 323 324 325 326 327 328 329 330 331 332 333 334 335 336 337 338 339 340 341 342 343 344 345 346 347 348 349 350 351 352 353 354 355 356 357 358 359 360 361 362 363 364 365 366 367 368 369 370 371 372 373 374 375 376 377 378 379 380 381 382 383 384 385 386 387 388 389 390 391 392 393 394 395 396 397 398 399 400 401 402 403 404 405 406 407 408 409 410 411 412 413 414 415 416 417 418 419 420 421 422 423 424 425 426 427 428 429 430 431 432 433 434 435 436 437 438 439 440 441 442 443 444 445 446 447 448 449 450 451 452 453 454 455 456 457 458 459 460 461 462 463 464 465 466 467 468 469 470 471 472 473 474 475 476 477 478 479 480 481 482 483 484 485 486 487 488 489 490 491 492 493 494 495 496 497 498 499 500 501 502 503 504 505 506 507 508 509 510 511 512 513 514 515 516 517 518 519 520 521 522 523 524 525 526 527 528 529 530 531 532 533 534 535 536 537 538 539 540 541 542 543 544 545 546 547 548 549 550 551 552 553 554 555 556 557 558 559 560 561 562 563 564 565 566 567 568 569 570 571 572 573 574 575 576 577 578 579 580 581 582 583 584 585 586 587 588 589 590 591 592 593 594 595 596 597 598 599 600 601 602 603 604 605 606 607 608 609 610 611 612 613 614 615 616 617 618 619 620 621 622 623 624 625 626 627 628 629 630 631 632 633 634 635 636 637 638 639 640 641 642 643 644 645 646 647 648 649 650 651 652 653 654 655 656 657 658 659 660 661 662 663 664 665 666 667 668 669 670 671 672 673 674 675 676 677 678 679