Need help in creating workspace like appinventor


i am working to make a webpage to write program using blockly.

i used the following files to create the workspace:

  • Blockly_compressed.js
  • Blocks_compressed.js
  • javacsript_compressed.js
  • en.js

from the google blockly repository

so i created workspace using


then i got the following workspace

But i need to integrate:

  1. Toolbar like :arrow_right: Screenshot_2020-08-11 MIT App Inventor(2)

  2. Warnings and errors like :arrow_right: Screenshot_2020-08-11 MIT App Inventor(1)

  3. Backpack :arrow_right: Screenshot_2020-08-11 MIT App Inventor

finally the workspace should be as following

i refered to blockly docs but didn't found anything .i found it in app inventor open source github repository but unable to understand the procedure how to integrate in my code using javascript

i need only Blocks part not the designer part from appinventor


Advanced thanks

What have you tried so far? The App Inventor specific extensions to Blockly are stored in the blocklyeditor subdirectory of the sources. You'll want to look at the files related to the backpack, warning indicator, and warning handler.

The toolbar you indicate is a GWT Tree. If you're not comfortable writing Java code, you may want to look for an alternative Tree widget, such as the one provided by the Google Closure Library.

Be aware that our sources are over 3 years out of date with Blockly, so it's probably not as easy as just pulling in our implementations of classes and having them magically work.

Thanks for your response.

so far we checked the above files you mentioned above and imported in my website and tried to integrate the backpack using

    var opts={

	collapse : true,
	disable : true,  
	trashcan : true, 

	css : true, 	
	rtl : false, 
	scrollbars : true, 
	sounds : true, 

`  Blockly.Backpack(Blockly.getMainWorkspace(),opts);`

but after adding above line to code getting this error

i can't the error can u please solve it please

all the code is in javascript only....

i have tried many but same error as this

please can u solve it

Can u help me with this error solving please

Our backpack code relies on an older version of the Blockly Flyout class. You'll probably need to rework some of the code if you're targeting a newer version of Blockly.

Yes thank you now to add backpack in workspace can u get me the procedure please

What I tried is

1.imported backpack.js & backpackflyout.js & workspaceSVG.js

In main js file I created a workspace
var workspace = Blockly.inject('div', options) ;
Blockly.workspaceSVG.prototype.addbackpack() ;

Getting an error i.e.,

this.options.readOnly is undefined

in this function in the WorkspaceSvg.js library

Can u give me a detailed guide to proceed the Integration please

Yes thank you now to add backpack in workspace can u get me the procedure please

What I tried is

1.imported backpack.js & backpackflyout.js & workspaceSVG.js

In main js file I created a workspace
var workspace = Blockly.inject('div', options) ;
Blockly.workspaceSVG.prototype.addbackpack() ;

Getting an error i.e.,

this.options.readOnly is undefined

in this function in the WorkspaceSvg.js library

Can u give me a detailed guide to proceed the Integration please

I'm not sure there's any more detailed integration than the code that is already there that brings together our code and Blockly's code.

What does your options object look like? The error suggests that you haven't constructed it properly.

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i made a try and got the output as below

but with few errors like

typeblock.js:712 Uncaught TypeError: Cannot read property 'ArrayMatcher' of undefined
at typeblock.js:712

and in Blockly.ai_inject function in blocklyeditor.js line number:435

if condition is not working because

in workspace i can see the injected as true
but when i try workspace.injected it returns undefined

when i click on show warnings i get this error

Uncaught TypeError: window.parent.BlocklyPanel_callToggleWarning is not a function
at Blockly.WarningIndicator.onclickWarningToggle (warningIndicator.js:262)
at SVGGElement.e (blockly_compressed.js:18623)

And also the backpack flyout is in black colour

so if it is solved then my project is almost completed

Thank you.................

Typeblock makes use of the Google Closure Library's Autocomplete widget (the ArrayMatcher error). Newer versions of Blockly aren't built on the closure library any more, so you'll need to include that separately. There are also a number of functions that glue our Blockly workspace to the rest of the App Inventor UI. You'll need to mock those out and/or remove that functionality (anything beginning with BlocklyPanel_).

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// Set separators depends on this.multi_ being set correctly

this.setSeparators(opt_separators ||;

this is undefined here

i have done that u told in the first point but i didnt get u the second point in here

and error is like this

inputhanler.js 138 is "this"
inputhandler.js 139 uis the error

if I try to remove that line other error at this.autocomplete , this is undefined occurs then removed it even, got everything good with no errors but also no workspace found

i have tried to export a block as png using below code


  • Exports the block as a PNG file with the Blockly XML code included as a chunk in the PNG.
  • @param {!Blockly.BlockSvg} block the block to export
    Blockly.exportBlockAsPng = function(block) {
    var xml = document.createElement('xml');
    xml.appendChild(Blockly.Xml.blockToDom(block, true));
    var code = Blockly.Xml.domToText(xml);
    svgAsDataUri(block.svgGroup_, block.workspace.getMetrics(), null, function(uri) {
    var img = new Image();
    img.src = uri;
    img.onload = function() {
    var canvas = document.createElement('canvas');
    canvas.width = 2 * img.width;
    canvas.height = 2 * img.height;
    var context = canvas.getContext('2d');
    context.drawImage(img, 0, 0, img.width, img.height, 0, 0, canvas.width, canvas.height);

function download(png) {
for (var i = 0; i < png.chunks.length; i++) {
var phy = [112, 72, 89, 115];
if (png.chunks[i].type == 'pHYs') {
png.chunks.splice(i, 1, new PNG.Chunk(9, 'pHYs', pHY_data, crc32(phy.concat(pHY_data)))); //replacing existing pHYs chunk
} else if (png.chunks[i].type == 'IDAT') {
png.chunks.splice(i, 0, new PNG.Chunk(9, 'pHYs', pHY_data, crc32(phy.concat(pHY_data)))); // adding new pHYs chunk
var blob = png.toBlob();
var a = document.createElement('a'); = (block.getChildren().length === 0 ? block.type : 'blocks') + '.png'; = '_self';
a.href = URL.createObjectURL(blob);
a.addEventListener("click", function(e) {

if (canvas.toBlob === undefined) {
var src = canvas.toDataURL('image/png');
var base64img = src.split(',')[1];
var decoded = window.atob(base64img);
var rawLength = decoded.length;
var buffer = new Uint8Array(new ArrayBuffer(rawLength));
for (var i = 0; i < rawLength; i++) {
buffer[i] = decoded.charCodeAt(i);
var blob = new Blob([buffer], {'type': 'image/png'});
new PNG().readFromBlob(blob, download);
} else {
canvas.toBlob(function (blob) {
new PNG().readFromBlob(blob, download);

but got an error at svgAsDataUri is not a function

unable to rectify it need help
thanks in advance

Hai Mr ewpatton thank q for your guide in developing the appinventor workspace it's done now .

But i am making block from block factory as json do i need to make any changes in it to work with show warning and errors because it's not working properly now

With this solution my project will be completed ..

Thank q so much

could u please help me to how make the code to get variables and procedures and also the warnings&error


i made a try like above got the instance but getting wrong error postioning on the block like in the image above

**when i click on the "show Warnings" it gives an error at this funtion **

Blockly.WarningIndicator.prototype.onclickWarningToggle = function() {




and the error is at line window.parent.BlocklyPanel_callToggleWarning(); Error goes here as parent.BlocklyPanel_callToggleWarning() function not found

when i try for variables all worked fine, but the problem is with "local_declaration_expression" variable and the error is as in below image

also to handle the procedure and the variables on the workspace on drag

i tried a lot to solve this failed can u help me in solving please.........

it will be helpfull if u could make steps to follow in an order please

thank you............

I've already explained previously that any function names starting with BlocklyPanel_ will need to be mocked out. They are provided by the designer side of App Inventor and so you need to provide some naive implementation, even if it does nothing.

As for the other error, you need to grab the code for indented inputs from the App Inventor blockly sources. These are patches on top of Blockly core.

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ok first one is clear

but i didnt get u at the second point
can u please tell me how to do that

and i dont understand why the error indication on the block is at wrong postion
where as warning indication is at correct position

i am missing any mandatory file to import if yes could u tell me what are those
thank you.....

Regarding the second item, we have additional modifications to Blockly that exist as part of our own fork of Blockly ( I've written a port of the indented input functionality on a newer version of Blockly last year, which is available as a pull request against the main Blockly repo. You may be able to apply these patches to the latest version of Blockly and rebuild it. Between our current master and Blockly's master, the Blockly team did a significant refactor of the rendering code. The PR I linked should be compatible with the more recent versions.

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yes i am done, but when i drag a lexical variable on workspace, this happens


i found there is no code for this type of blocks as getting undefined in blockly compressed.js, also i need variable like 'var' as javascript
ex:- var example;
not the android studio variables


if i use the local_declaration_expression i am getting above error

most importantly
how to set variables on events like below

this are my unsolved errors

can u mention the error for each solution please and thank you

Regarding error 1, our variable system works different from Blockly's. If you're using our blocks to build a workspace to create JavaScript, you'll need to write generator code for each of the blocks that goes beyond Blockly's built-in blocks.

Regarding error 2, I've already explained that our version of Blockly has input types beyond what Google provides. I pointed you to the pull request that fixes this, and I explained that you would need to build your own version of Blockly with those changes applied if you wanted this to work. I continue to stand by those claims.

Regarding error 3, I have no idea what you mean by this line of inquiry.

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