Question Quad is turing black when changing it's texture in unity

I am building an Android application, which will read images from '/sdcard/Documents/' and then display them on a Quad, using unity3D. When I test the app inside Unity in play mode (using images from an external path), the texture of the quad is updated according to the image, but when I build the APK and test it on the device, the quad turns black.

Here's the code I am using:

Code (CSharp):

1. public class ShowImage : MonoBehaviour {
2.    [SerializeField] GameObject quad;
3.    int count = 0;
4.    Material quadMaterial;
5.    string extPath;
6.  
7.    void Start() {
8.        AndroidJavaClass envClass = new AndroidJavaClass("android.os.Environment");
9.        AndroidJavaObject extStorageDir = envClass.CallStatic<AndroidJavaObject>("getExternalStorageDirectory");
10.        extpath = extStorageDir.Call<string>("getAbsolutepath");
11.        quadMaterial = quad.GetComponent<Renderer>().material;
12.    }
13.  
14.    void Update() {
15.        if (File.Exist($"{extPath}/Documents/temp_{count}.png")) {
16.            byte[] imageData = File.ReadAllBytes($"{extPath}/Documents/temp_{count}.png");
17.            Texture2D texture = new Texture2D(2, 2);
18.            // Texture2D texture = new Texture2D(2, 2, TextureFormat.ARG32, true);
19.            texture.LoadImage(imageData);
20.            // ImageConversion.LoadImage(texture, imageData, true);
21.            quadMaterial.mainTexture = texture;
22.            count++;
23.        }
24.    }
25. }

I put some debug statements also, the image is being read, as imageData.Length is returning the correct value. Also, I am not getting any errors, I checked the logs using ADB.

 

Not fully sure, but you can check to see if this post gives any clarity:
https://discussions.unity.com/t/unity-android-build-missing-resources/232905

Other than that I can only recommend revisiting the manual:
https://docs.unity3d.com/Manual/android-BuildProcess.html

 

Sounds like you wrote a bug!!

Stop trying to load one picture per frame (the code above) and get ONE PICTURE loaded and displayed.

Until you have that there's no point in loading one every frame.

Review the paths you're using, the lists of files, etc.

Time to start debugging! Here is how you can begin your exciting new debugging adventures:

You must find a way to get the information you need in order to reason about what the problem is.

Once you understand what the problem is, you may begin to reason about a solution to the problem.

What is often happening in these cases is one of the following:

- the code you think is executing is not actually executing at all
- the code is executing far EARLIER or LATER than you think
- the code is executing far LESS OFTEN than you think
- the code is executing far MORE OFTEN than you think
- the code is executing on another GameObject than you think it is
- you're getting an error or warning and you haven't noticed it in the console window

To help gain more insight into your problem, I recommend liberally sprinkling

Debug.Log()

statements through your code to display information in realtime.

Doing this should help you answer these types of questions:

- is this code even running? which parts are running? how often does it run? what order does it run in?
- what are the names of the GameObjects or Components involved?
- what are the values of the variables involved? Are they initialized? Are the values reasonable?
- are you meeting ALL the requirements to receive callbacks such as triggers / colliders (review the documentation)

Knowing this information will help you reason about the behavior you are seeing.

You can also supply a second argument to Debug.Log() and when you click the message, it will highlight the object in scene, such as

Debug.Log("Problem!",this);

If your problem would benefit from in-scene or in-game visualization, Debug.DrawRay() or Debug.DrawLine() can help you visualize things like rays (used in raycasting) or distances.

You can also call Debug.Break() to pause the Editor when certain interesting pieces of code run, and then study the scene manually, looking for all the parts, where they are, what scripts are on them, etc.

You can also call GameObject.CreatePrimitive() to emplace debug-marker-ish objects in the scene at runtime.

You could also just display various important quantities in UI Text elements to watch them change as you play the game.

Visit Google for how to see console output from builds. If you are running a mobile device you can also view the console output. Google for how on your particular mobile target, such as this answer for iOS: https://forum.unity.com/threads/how-to-capturing-device-logs-on-ios.529920/ or this answer for Android: https://forum.unity.com/threads/how-to-capturing-device-logs-on-android.528680/

If you are working in VR, it might be useful to make your on onscreen log output, or integrate one from the asset store, so you can see what is happening as you operate your software.

Another useful approach is to temporarily strip out everything besides what is necessary to prove your issue. This can simplify and isolate compounding effects of other items in your scene or prefab.

If your problem is with OnCollision-type functions, print the name of what is passed in!

Here's an example of putting in a laser-focused Debug.Log() and how that can save you a TON of time wallowing around speculating what might be going wrong:

https://forum.unity.com/threads/coroutine-missing-hint-and-error.1103197/#post-7100494

"When in doubt, print it out!(tm)" - Kurt Dekker (and many others)

Note: the

print()

function is an alias for Debug.Log() provided by the MonoBehaviour class.