How to convert String to Uri if it has % in it?-CodePudding

I have problems converting this string "content://com.android.providers.media.documents/document/image:1000002538" into a Uri correctly.

The Situation:

I decremented a Uri

First, I converted the Uri into a string and in turn into an int

Afterwhich, I did a -1, and then I got the string that looks exactly like a decremented string

However, when I parse the uri and try to setImageURI() on it,

it is showing "File error accessing recents directory (directory
doesn't exist?)."

Here is the code that I have used:

            Uri ImageUri = data.getData();
            String uri1 = ImageUri.toString();

            //region uri2
            String substr1 = uri1.substring(uri1.length()-3);
            int substr1int = parseInt(substr1)-1;
            String decrementedstr1 = new Integer(substr1int).toString();
            int numberofchars1 = uri1.length()-3;
            String firstcomponent1 = uri1.substring(0, numberofchars1);
            String uri2 = firstcomponent1   decrementedstr1;


            //endregion
            Uri test = Uri.parse(uri2);
            animateobject.setImageURI(test);

Got this Error:

File error accessing recents directory (directory doesn't exist?).

CodePudding user response：

Try to use toString() method to convert into the string.

CodePudding user response：

Let's first get something straight. What is the meaning of that % character?

Well ... if you look at the URI Specification (RFC ....) the % is a percent encoding marker. The two characters after the % are hex digits, and the whole thing represents an ASCII character. In fact, : represents the colon character (:). So the unencoded path component of that URI is actually

content://com.android.providers.media.documents/document/image:1000002538

So the image (document) number is really 1000002538 and decrementing it should presumably give 1000002537 as the image number.

I think that your version of the code is failing because you are (in effect) double encoding the %. That results in the "consumer" of this URI seeing a garbled path. Also, you are decrementing just the last 3 digits of the image numbers ... and your example has 4 significant digits on the right end.

So here's how you should code it:

        Uri imageUri = data.getData();
        String[] pathSegments = imageUri.getSchemeSpecificPart().split("/");
        String lastSegment = pathSegments[pathSegmentslength - 1);

        String[] parts = lastSegment.split(":");
        assert parts.length == 1 && "image".equals(parts[0]);
        long imageNo = Long.parseLong(parts[1]);
        imageNo--;
        lastSegment = "image:"   imageNo;

        pathSegments[pathSegments.length - 1] = lastSegment;
        String path = String.join("/", pathSegments);
        imageUri = Uri.Builder().scheme("content").opaquePart(path).build();

CAVEAT - this code is not compiled or tested. I don't have an Android dev platform.