How to Make Android Apps 8 : Make An Android App

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Get the Code Here :

( Use version 19 of the emulator to run the app! I made a mistake saying to use 20 in the video )

In this tutorial we take it to the next level. In the last video we designed the interface for our Android conversion app. This time we will create the whole backend and finish the app.

The goal of this tutorial is to show you how to make an entire app in one video. We’ll cover use case descriptions, activity diagrams, class diagrams, flexible ways to solve our conversion problem, dynamically changing classes and much more. If you don’t understand everything don’t worry about it. This tutorial is all about seeing it all so you’ll grasp what is coming next.


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38 responses to “How to Make Android Apps 8 : Make An Android App”

  1. Semir Umut Kurt Avatar

    to be honest that in the beginning I thought that there will be number of equations which are equal to 6 choose 2 combinations

  2. Semir Umut Kurt Avatar

    ActionBarActivity is depreciated , use AppCompatActivity bicoz of somelines we wrote in mainActivity xml and manifest I guess

  3. エレダー Avatar

    too many retard on this world, just destroy the world, your video is already good enough, just have some small problem about code in some of your app, and they ask about zoom?, retard, destroy this world please God

  4. Albin Thomsson Avatar

    I really just find myself trying to memorize functions and keywords, any tips?

  5. Cory No Avatar

    I love these tutorials.
    I would say if Zoom is going to stay make sure that you scroll the file out of zoom that way I can understand the flow of the file and what goes where etc. I think that is the biggest issue for myself. Otherwise thank you so much for putting your time and effort into making these videos! It's much appreciated you're doing a great job!

  6. Eric Ho Avatar

    so many variables, so complicated

  7. Lee Cant Avatar

    I prefer Zooming Derek, I think you'll find people's opinions a rather even on this matter.
    I must say it's a long time since i've seen UML, I guess it's fairly necessary for complex solutions.

    Do you ever find yourself using Pseudocode much?

  8. Krystaphel Reid Avatar

    Hey man, terrific videos! They rock. I'm wanting to build a wallpaper app and I'm not sure how to do it.

    I downloaded 113 different images from google that i want to use in the app, i then added all of them to the drawable folder but when i'm inserting them I realize that android studio is saying the images take up too much space.

    The pictures are 15mb in all. I wanna know how to create an app that can show all of the high quality pictures i downloaded from google, could you do a tutorial for me? Help is needed!

  9. Abit Sen Avatar

    will u do a tutorial on how to build an app where the users of the app will be able to sign up an account for the specific app?

  10. yoav tamir Avatar

    Wow! You are amaizing!
    , i just scrolled through the comment and you accually respond to most people:000
    (:It just shows you really care about your viewers

    continue with geat videos and good luck(;

  11. Jack Dando Avatar

    I'm getting a message that unit and value haven't been initializes in Quantity.java :/

  12. FeeldaFia Avatar

    Why did you add a d after all the values inside of the enum?

    tsp(1.0d), tbs(0.333d), cup(0.0208d), oz(0.1666d), pint(0.0104d), quart(0.0052d),
    gallon(0.0013d), pound(0.0125d), ml(4.9289d), liter(0.0049d), mg(5687.5d), kg(0.0057d)

  13. Richard Melcher Avatar

    It's really distracting when you zoom in and out constantly. I lose my place in the document cant see all your code.

  14. Lucas Wang Avatar

    Hey Derek,
    I really enjoy your videos, but i had a few questions about this program. First, I realize that the conversion is based upon the text in the edittext field. This means that its impossible to put a hint in the field instead of text. Is there a way to fix this and replace the text with a hint? Also, is it ok if I borrow your code for an app I'm working on? I wont graft the code verbatim, but my layout will be the same. Is that fine with you?

  15. Peteman12 Avatar

    I included a button that lets me convert without having to click the spinner again.

    This is the code I used (making a button on the activity_main.xml is pretty simple).

        public void activateConversion(View view) {
            String itemSelectedInSpinner =unitTypeSpinner.getSelectedItem().toString();
            checkIfConvertingFromTsp(itemSelectedInSpinner);

        }

  16. GabbeSWE0 Avatar

    Thank you! Great vid as always. I do like the zoom, I'm watching this on a 5 inch smart phone 🙂

  17. Mohammad Rajaul Islam Avatar

    Hi, Thanks for your nice tutorial. I use Eclipse IDE and I have completed everything according to your video and there is no error. In android Manifest file, I have used:
     <uses-sdk
            android:minSdkVersion="14"
            android:targetSdkVersion="21" />

    and I do not see any error in console but I see, at emulator , Unfortunately  Conversion has stopped.
    Any suggestions please.

  18. Gabriel Cole Avatar

    Derek your videos are very useful. I watched 1/4 of your java tutorial and is awesome.
    In this video tutorial I have an error in the code and it looks like this:
    17779-17779/com.example.android.convertidordeunidades E/AndroidRuntime﹕ FATAL EXCEPTION: main
        java.lang.NumberFormatException: Invalid double: ""
                at java.lang.StringToReal.invalidReal(StringToReal.java:63)
                at java.lang.StringToReal.parseDouble(StringToReal.java:248)
                at java.lang.Double.parseDouble(Double.java:295)
                at com.example.android.convertidordeunidades.MainActivity.updateUnitTypesUsingM(MainActivity.java:106)
                at com.example.android.convertidordeunidades.MainActivity.checkIfConvertingFromM(MainActivity.java:86)
                at com.example.android.convertidordeunidades.MainActivity$1.onItemSelected(MainActivity.java:73)

    line 106 looks like this: double doubleToConvert = Double.parseDouble(amountTextView.getText().toString());
    line 86: updateUnitTypesUsingM(Quantity.Unit.m);
    line 73: checkIfConvertingFromM(itemSelectedInSpinner);

    P.D.: I'm not using the same units that are in the video

  19. Kimti Patel Avatar

    Hi "Not zooming" is much better for me as well, I don't get lost about where you jumping in screen so quickly. But really appreciate your effort for these videos. Thank you

  20. Lucas Wang Avatar

    Please stop zooming in, it makes it harder to follow. Thanks!

  21. Charles Custer Avatar

    Hi Derek, I know I am late to the game, but wanted to thank you so much.  Your video tutorials are great.  On the "To Zoom or Not To Zoom…"  I would vote not to Zoom.  Gets me a bit dizzy.

  22. Ervin Casiguran Avatar

    help +Derek Banas i really do not understand the private Unit(double inTsp) method (or constructor?) 

    i don't quite understand how the byBaseUnit gets instantiated with a value and how .to(Unit newUnit) can call fromBaseUnit and toBaseUnit without instantiating the value of byBaseUnit in public enum Unit

    or if someone could help that would be great..

    i've been trying to understand this for 2 hours now and i still don't quite get it.

  23. Jim Aven Avatar

    Not sure what im missing here. In MainActivity you define updateUnitTextFieldUsingTsp using 3 args. When you place into the updateUnitTypeUsingOther you use 4. This video moves fast but I looked at the code and it reflects the same. What am i missing?

  24. Kevin Gresmer Avatar

    Can you break down whats happening in detail in this return value?

     public Quantity to(Unit newUnit) {
            Unit oldUnit = this.unit;
            return new Quantity(newUnit.fromBaseUnit(oldUnit.toBaseUnit(value)), newUnit);
        }

  25. Felix Garay Avatar

    Android Studio 1.2, Awesome Stuff! I agree its a bit fast paced, but managed to complete the app. Only looked at the link to the code for debugging. I found that the TextViews' id prefixes must match the enum states, tsp, tbs, cup, oz etc.. Otherwise priiiiity goood! Oh… I almost forgot, the Zoomin for me at least is kind bothersome, because I am listening to you type and explain as I type code, and every now an then I get stumped and look up and cant see all the code, so I rewind and pause.

  26. Uzma Rauf Avatar

    Hi Derek,
    I get the error in logCat " W/EGL_emulation﹕ eglSurfaceAttrib not implemented" and nothing gets loaded in spinner. I am using emulator instead of an android device. Couldn't find anything online to fix the issue. I hope you can help.

  27. Webalergy Avatar

    Your tutorials make me wanna hug the hell out of you! Thanks a ton for taking the time to make these videos, you are helping out a lot 🙂 I never programmed before, and 8 videos later I got a textView and 4 buttons and thanks to you I know how to align them and edit them and make them do something 😀 keep up with amazing work, I'll make sure to recommend you to everyone!

  28. Hishmad Abubakar Al Amudi Avatar

    Hi Derek, well,  I got an error in the MainActivity.java, all the R turns red!!! however I am using Android Studio 1.2

  29. Shashank Bhardwaj Avatar

    This is where it got way too tough for me to understand. Hope I can keep up with the videos that follow.

  30. Anders Rapp Avatar

    Wow. After duplicating the same code but changing between tsp and eleven other units for the THOUSAND time…I stopped. I just wanted to learn to use a spinner, not build an app to run an entire dairy farm. 🙂

  31. techtutor Avatar

    Thank you so much for creating the diagram. This simplified everything for all of us!

  32. Felds Liscia Avatar

    I'm sorry for nitpicking but you got me really curious: I noticed you can convert liters to kg; since one is a measurement of volume and the other one of mass, how can you convert from one to the other? it could be done if we are talking about water (1l = 1kg (metric system FTW)), but the ratios are different on the enum. BTW, awesome tutorial as aways!! 🙂

  33. Paulo Henrique Avatar

    "What is working perfectly fine, make the code more readable. Do whatever works for you… Allrighhhht"
    I like the way you talk, it's funny.
    Nice tutorial! 

  34. kevinb123b Avatar

    So my app seems to work fine, but when I click to convert from cups my app shuts down, do you know why this could be?

    NEVERMIND: I figured it out, I had the Unit named cups in my Quantity class, and in my method checkIfConvertingFromTsp I had the "else if" statement having the condition that if the equaled to "cup", I just removed the "s" from my quantity class and in the method and it fixed everything

  35. anton mitkov Avatar

     Sorry for taking your time, but I've got one question. I'm new in Android development and I start learning with your video. And that point of time I'm on that video ( How to Make Android Apps 8 : Make An Android App ), but unfortunately I can't run it on my devise. I'm using HTC oneV – android version 4.0.3, Sense 4.0 also it's written "HTC SDK API level 4.11". In the project my minSDKVersion is 8. So the problem is when I run the app on my phone it says "Sorry but Conversion" stops working.

  36. DERLETSPLAYER Avatar

    Hi Derek,

    thanks for your amazing vids!
    Buuut..beginning at this part i don't understand nothing. I don't know, should i learn Java a bit better?

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