Develop Reference

DIfference between Uri.fromParts and Uri.parse?

I'm creating an Intent for Android, to send e-mails.
And I'm getting confused about the behavior of Uri.fromParts.
Mi code:
This works fine!
uri=Uri.parse(
"mailto:" + toAddress +
(subject != null ?
("?" + "subject=" + Uri.encode(subject)) :
"")
The previous work fine, and create an Uri in the form mailto:john#doe.com?subject=Test
But if I try to use Uri.from parts, with this sample:
uriBuilder=Uri.fromParts("mailto",toAddress,null).buildUpon();
if (subject!=null) {
uriBuilder.appendQueryParameter("subject",subject);
}
uri=uriBuilder.build();
I get an error. The final uri is mailto:?subject=Test
The intermediate is correct, but when I use appendQueryParameter, it removes the content after the mailto scheme.
Do you know why? Which is the canonical way to do this?

Uri#fromParts()
Creates an opaque Uri from the given components. Encodes the ssp which means this method cannot be used to create hierarchical URIs.
When you call buildUpon() on this, the Builder contains the scheme, scheme-specific part (ssp) and the fragment (null in your case).
appendQueryParameter() then turns the Builder to a hierarchical one, deleting the opaque ssp data.
I don't think there's a "canonical" way. Just don't mix hierarchical and opaque builders.
For details on what happens under the hood, read the source.

Android Webview POST request

I'm trying to do a post request with a WebView on Android.
After searching for days and trying dozens of things i couldn't get it work. In SWIFT it's just a few lines of code so i thought there must also be a simple way to do a post request for a webview on android.
As (for 2016) EncodingUtils and HTTPClient are deprecated this are my current approaches:
String url = "http://example.com/php.php";
String postData = null;
postData = "param1=" + URLEncoder.encode("1234567890", "UTF-8");
webcontent.postUrl(url,postData.getBytes());
//or
webcontent.postUrl(url, Base64.encode(postData.getBytes(), Base64.DEFAULT));
Both just result in a blank screen. There is just one parameter to be sent and a string containing html from the server should be received.
In addition, the php on the server returns a html-string with colored background irrespective of any input, but even this isn't displayed so maybe the whole request never reaches the server?
Thanks in advance!

In Android you do not use webView to access the content of the HTTP response. You'll need to use HttpClient for that purpose!
See this nice tutorial which explains the fundamentals! Also see this video if you find it hard!
Hope it helps!

How do you resolve a relative Uri?

Given an absolute Uri and a relative Uri or relative path, how do you get the absolute Uri pointing to the relative location?
For example, suppose we have the Uri for file:///android_asset/dir, pointing to a location in our assets. Further suppose that elsewhere, we have a relative path of /foo. The absolute Uri for that relative path should be file:///android_asset/foo. Is there something on Uri, or elsewhere in the Android SDK, that I am missing that give me that result Uri?
Uri.withAppendedPath() is not the answer, as all it seems to do is handle trailing directory separators:
Uri abs=Uri.parse("file:///android_asset/");
Uri rel=Uri.withAppendedPath(abs, "/foo");
Assert.assertEquals("file:///android_asset/foo", rel.toString());
// actually returns file:///android_asset//foo
Uri abs2=Uri.parse("file:///android_asset/dir");
Uri rel2=Uri.withAppendedPath(abs2, "/foo");
Assert.assertEquals("file:///android_asset/foo", rel2.toString());
// actually returns file:///android_asset/dir//foo
Uri.Builder, via buildUpon() on Uri, is not an improvement:
Uri rel3=abs.buildUpon().appendPath("/foo").build();
Assert.assertEquals("file:///android_asset/foo", rel3.toString());
// actually returns file:///android_asset/%2Ffoo
Uri rel4=abs.buildUpon().appendEncodedPath("/foo").build();
Assert.assertEquals("file:///android_asset/foo", rel4.toString());
// actually returns file:///android_asset//foo
In a pinch I can try using java.net.URL and its URL(URL context, String spec) constructor, or just roll some code for it, but I was hoping to stay in the realm of Android Uri values if possible, just for any quirks differentiating URL and Uri.

Android doesn't make this easy.
In my case, I had to take a base url that may or may not have an included path:
http://www.myurl.com/myapi/
...and append a REST API method path, like:
api/where/agencies-with-coverage.json
...to produce the entire url:
http://www.myurl.com/myapi/api/where/agencies-with-coverage.json
Here's how I did it (compiled from various methods within the app - there may be a simpler way of doing this):
String baseUrlString = "http://www.myurl.com/myapi/";
String pathString = "api/where/agencies-with-coverage.json";
Uri.Builder builder = new Uri.Builder();
builder.path(pathString);
Uri baseUrl = Uri.parse(baseUrlString);
// Copy partial path (if one exists) from the base URL
Uri.Builder path = new Uri.Builder();
path.encodedPath(baseUrl.getEncodedPath());
// Then, tack on the rest of the REST API method path
path.appendEncodedPath(builder.build().getPath());
// Finally, overwrite builder with the full URL
builder.scheme(baseUrl.getScheme());
builder.encodedAuthority(baseUrl.getEncodedAuthority());
builder.encodedPath(path.build().getEncodedPath());
// Final Uri
Uri finalUri = builder.build();
In my case, the Builder classes for the API client code assembled the path prior to combining it with the baseURL, so that explains the order of things above.
If I've pulled together the above code correctly, it should handle port numbers as well as spaces in the URL string.
I pulled this source code from the OneBusAway Android app, specifically the ObaContext class. Note that this code on Github also handles the additional case where the user typed in a baseUrl (String serverName = Application.get().getCustomApiUrl() in the above code) that should override the region base URL (mRegion.getObaBaseUrl()), and the user-entered URL may not have http:// in front of it.
The unit tests that pass for the above code on Github, including cases where port numbers and spaces are included in the baseUrl and path, and the leading/trailing / may or may not be included, are here on Github. Related issues on Github where I was banging my head on the wall to try and get this all to work - 72, 126, 132.
I haven't tried this with non-HTTP URIs, but I believe it may work more generally.

There is an equivalent to urllib.parse.urljoin (Python) in Android URI.create(baseUrl).resolve(path).
import java.net.URI
URI.create("https://dmn92m25mtw4z.cloudfront.net/helpvids/f3_4/hls_480/480.m3u8")
.resolve("0.ts")
// output:
// https://dmn92m25mtw4z.cloudfront.net/helpvids/f3_4/hls_480/0.ts
Sean Barbeau answer returns wrong URL, it's just appending the 0.ts to the url.

Mystery URL decoding of certain characters - Android URI / Google App Engine

I am having a curious problem that perhaps someone has insight into. I encode a query string into a URL on Android using the following code:
request = REQUEST_BASE + "?action=loadauthor&author=" + URLEncoder.encode(author, "UTF-8");
I then add a few other parameters to the string and create a URI like this:
uri = new URI(request);
At a certain point, I pull out the query string to make a checksum:
uri.getRawQuery().getBytes();
Then I send it on its way with:
HttpGet get = new HttpGet(uri);
On the Appengine server, I then retrieve the string and try to match the checksum:
String query = req.getQueryString();
Normally, this works fine. However, there are a few characters that seem to get unencoded on the way to the server. For example,
action=loadauthor&author=Charles+Alexander+%28Ohiyesa%29+Eastman&timestamp=1343261225838&user=1479845600
shows up in the server logs (and in the GAE app) as:
action=loadauthor&author=Charles+Alexander+(Ohiyesa)+Eastman&timestamp=1343261226837&user=1479845600
This only happens to a few characters (like parentheses). Other characters remain encoded all the way through. Does anyone have a thought about what I might be doing wrong? Any feedback is appreciated.

I never did find a solution for this problem. I worked around it by unencoding certain characters on the client before sending things to the server:
request = request.replace("%28", "(");
request = request.replace("%29", ")");
request = request.replace("%27", "'");
If anyone has a better solution, I am sure that I (and others) would be interested!

URLEncoder does not encode parentheses and certain other characters, as they are supposed to be "safe" for most servers. See URLEncoder. You will have to replace these yourself if necessary.
Example:
URI uri = new URI(request.replace("(","%28"));
If a lot of replacements are needed, you can try request.replaceAll(String regularExpression, String replacement). This, of course, requires knowledge of regular expressions.

Size limit of a String while posting to server

I am posting a string to server. If string size is up to 6000KB then its posted successfully. But when size exceeded more than this its showing response -1.
I have tried method of posting: syn_data1 is string . records fetch from data base and then appending to A string builder and finally i create synData1 string from String builder
URL url = new URL(syn_data1);
URLConnection urlc = url.openConnection();
HttpURLConnection huc = (HttpURLConnection)urlc;
huc.setRequestMethod("POST");
huc.setConnectTimeout(3000);
huc.connect();
int response = huc.getResponseCode();
I do care about each special character and remove.But I did not get success

In theory, the URI in an HTTP request can be of any length, but the practical limit is on the order of 2k. Please read here for more info on that.
I am assuming the length is coming from the query string parameters (those name=value pairs that come after the ?). You should be putting these in the POST data, leaving the path part of the URI only. Of course, the server will have to be looking for those parameters in the POST data as well.

Are you passing the NameValue pairs properly . This is one successful way which i use .
List<NameValuePair> loginParams = new ArrayList<NameValuePair>(1);
loginParams.add(new BasicNameValuePair("ColumnName In DB",YourString));
then you do
httppost.setEntity(new UrlEncodedFormEntity(loginParams));
and proceed to execute

It's not clear exactly what you're trying to achieve, but this definitely looks wrong:
URL url = new URL(syn_data1.toString());
URLEncoder.encode(syn_data1.toString(),"UTF-16BE");
If syn_data1 is already a string, you don't need to call toString on it.. and calling URLEncoder.encode doesn't have any side-effects, so the second statement is pointless. Perhaps you want:
URL url = new URL(URLEncoder.encode(syn_data1, "UTF-16BE"));
That's just on the encoding side though - you still shouldn't be trying to use enormous URLs. If you have a lot of data, that should be in the body of the request rather than the URL.