Android NestedScrollView

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Android NestedScrollView

original source: http://ivankocijan.xyz/android-nestedscrollview/

Android – NestedScrollView

Adding a ScrollView inside ScrollView can be difficult. Most of the times it won’t end well. You will end up adding few workarounds and a person maintaining your code will probably hate you for the rest of his life. Fortunately, with NestedScrollView class this becomes much easier.

If you ever tried this then you know that two things happen:

1. Lint will yell at you because you are adding vertically scrolling ScrollView inside another vertically scrolling widget.

2. It won’t work because only one ScrollView will be scrollable.

Using NestedScrollView

There are few workarounds you could add in order to get this to work but there is no need for that. Android support v4 library has a class called NestedScrollView and it does exactly what the name suggests. It can be used as both parent or child ScrollView.

Here is an example how to add it in your xml:

<ScrollView
       xmlns:android=“http://schemas.android.com/apk/res/android”
       android:layout_width=“match_parent”
       android:layout_height=“match_parent”>

   <LinearLayout android:layout_width=“match_parent”
                 android:layout_height=“wrap_content”
                 android:orientation=“vertical”>

       <android.support.v4.widget.NestedScrollView
               android:layout_width=“match_parent”
               android:padding=“@dimen/default_padding”
               android:layout_height=“@dimen/nested_scroll_view_height”>

           <TextView
                   android:text=“@string/hello_world”
                   android:layout_width=“wrap_content”
                   android:layout_height=“wrap_content”
                   android:textStyle=“bold”/>

       </android.support.v4.widget.NestedScrollView>

       <include layout=“@layout/cards_layout”/>

   </LinearLayout>
</ScrollView>

And that’s it. Lint won’t yell at you anymore and both ScrollViews will work. This is how it looks like:

Video Player00:0000:12

When to use NestedScrollView?

Most of the time you probably do not need two ScrollViews on the same screen, but if you ever need it NestedScrollView is a great solution. This class has a set of useful methods so you can disable nested scrolling, check if your nested scroll view has nested scrolling parent and so on… You can check out the official documentation for more info.

What does random.sample() method in python do?

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What does random.sample() method in python do?

original source : https://stackoverflow.com/questions/22741319/what-does-random-sample-method-in-python-do

According to documentation:

random.sample(population, k)

Return a k length list of unique elements chosen from the population sequence. Used for random sampling without replacement.

Basically, it picks k random elements, a sample, from a sequence:

>>> import random
>>> l = range(0, 100)
>>> l
[0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 29, 30, 31, 32, 33, 34, 35, 36, 37, 38, 39, 40, 41, 42, 43, 44, 45, 46, 47, 48, 49, 50, 51, 52, 53, 54, 55, 56, 57, 58, 59, 60, 61, 62, 63, 64, 65, 66, 67, 68, 69, 70, 71, 72, 73, 74, 75, 76, 77, 78, 79, 80, 81, 82, 83, 84, 85, 86, 87, 88, 89, 90, 91, 92, 93, 94, 95, 96, 97, 98, 99]
>>> random.sample(l, 10)
[12, 25, 21, 13, 61, 92, 90, 22, 84, 93]

How to deserialize a list using GSON or another JSON library in Java?

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How to deserialize a list using GSON or another JSON library in Java?

original source :https://stackoverflow.com/questions/4318458/how-to-deserialize-a-list-using-gson-or-another-json-library-in-java

Video[] videoArray = gson.fromJson(json, Video[].class);

This way you avoid all the hassle with the Type object, and if you really need a list you can always convert the array to a list, e.g.:

List<Video> videoList = Arrays.asList(videoArray);

IMHO this is much more readable.

How to parse JSON in Java

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How to parse JSON in Java

original source : https://stackoverflow.com/questions/2591098/how-to-parse-json-in-java

For the sake of the example lets assume you have a class Person with just a name.

private class Person {
    public String name;

    public Person(String name) {
        this.name = name;
    }
}

Google GSON

(

Maven

)

My personal favourite as to the great JSON serialisation / de-serialisation of objects.

Gson g = new Gson();

Person person = g.fromJson("{"name": "John"}", Person.class);
System.out.println(person.name); //John

System.out.println(g.toJson(person)); // {"name":"John"}

Update

If you want to get a single attribute out you can do it easily with the Google library as well:

JsonObject jsonObject = new JsonParser().parse("{"name": "John"}").getAsJsonObject();

System.out.println(jsonObject.get("name").getAsString()); //John

Org.JSON

(

Maven

)

If you don’t need object de-serialisation but to simply get an attribute, you can try org.json (or look GSON example above!)

JSONObject obj = new JSONObject("{"name": "John"}");

System.out.println(obj.getString("name")); //John

Jackson

(

Maven

)

ObjectMapper mapper = new ObjectMapper();
Person user = mapper.readValue("{"name": "John"}", Person.class);

System.out.println(user.name); //John

How to Work With JSON Data Using Python

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How to Work With JSON Data Using Python

original source: https://code.tutsplus.com/tutorials/how-to-work-with-json-data-using-python–cms-25758

This tutorial shows how easy it is to use the Python programming language to work with JSON data.

Before I begin the topic, let’s define briefly what we mean by JSON. Let’s see how JSON’s main website defines it:

JSON (JavaScript Object Notation) is a lightweight data-interchange format. It is easy for humans to read and write. It is easy for machines to parse and generate. It is based on a subset of the JavaScript Programming Language, Standard ECMA-262 3rd Edition – December 1999. JSON is a text format that is completely language independent but uses conventions that are familiar to programmers of the C-family of languages, including C, C++, C#, Java, JavaScript, Perl, Python, and many others. These properties make JSON an ideal data-interchange language.

Thus, JSON is a simple way to create and store data structures within JavaScript. The reason you see JavaScript in the acronym is due to the fact that a JavaScript object is created when storing data with JSON. But, don’t worry, you don’t need to know JavaScript to work with JSON files, rather it is about the JSON syntax (format) itself.

In brief, JSON is a way by which we store and exchange data, which is accomplished through its syntax, and is used in many web applications. The nice thing about JSON is that it has a human readable format, and this may be one of the reasons for using it in data transmission, in addition to its effectiveness when working with APIs.

An example of JSON-formatted data is as follows:

{"name": "Frank", "age": 39, "isEmployed": true}

In this tutorial, I will show you how to use Python to work with JSON files. So, let’s get started!

Python and JSON

Python makes it simple to work with JSON files. The module used for this purpose is the json module. This module should be included (built-in) within your Python installation, and you thus don’t need to install any external modules as we did when working with PDF and Excel files, for instance. The only thing you need in order to use this module is to import it:

import json


But, what does the json library do? This library mainly parses JSON from files or strings. It also parses JSON into a dictionary or list in Python and vice versa, that is converting a Python dictionary or list into JSON strings.

JSON to Python

Reading JSON means converting JSON into a Python value (object). As mentioned above, the json library parses JSON into a dictionary or list in Python. In order to do that, we use the loads() function (load from a string), as follows:

import json

jsonData = '{"name": "Frank", "age": 39}'

jsonToPython = json.loads(jsonData)


If you want to see the output, do a print jsonToPython, in which case you will get the following output:

{u'age': 39, u'name': u'Frank'}


That is, the data is returned as a Python dictionary (JSON object data structure). So, will the statement print jsonToPython['name'] return any output? Go ahead, try it out.

Python to JSON

In the previous section, we saw how to convert JSON into a Python value (i.e. Dictionary). In this section, I will show you how we can convert (encode) a Python value to JSON.

Say that we have the following Dictionary in Python:

import jsonpython

Dictionary = {'name':'Bob', 'age':44, 'isEmployed':True}

dictionaryToJson = json.dumps(pythonDictionary)


If we print dictionaryToJson, we get the following JSON data:

{"age": 44, "isEmployed": true, "name": "Bob"}


So this output is considered the data representation of the object (Dictionary). The method dumps() was the key to such operation.

It is important to note at this point that JSON cannot store all types of Python objects, but only the following types: Lists; Dictionaries; Booleans; Numbers; Character strings; and None. Thus, any other types need to be converted in order to be stored in JSON.

Let’s say we have the following class:

class Employee(object):    

     def __init__(self, name):        

         self.name = name


Let’s say we created a new object abder, as follows:

abder = Employee('Abder')

What if we wanted to convert this object to JSON? That is json.dumps(abder)? In this case, you would get an error similar to the following:

Traceback (most recent call last):  

File "test.py", line 8, in <module>    abderJson = json.dumps(abder)  

File "/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/__init__.py", line 243, in dumps    return _default_encoder.encode(obj)  

File "/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/encoder.py", line 207, in encode    chunks = self.iterencode(o, _one_shot=True)  

File "/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/encoder.py", line 270, in iterencode    return _iterencode(o, 0) 

 File "/usr/local/Cellar/python/2.7.10_2/Frameworks/Python.framework/Versions/2.7/lib/python2.7/json/encoder.py", line 184, in default    raise TypeError(repr(o) + " is not JSON serializable")

TypeError: <__main__.Employee object at 0x10e74b750> is not JSON serializable


But, is there a workaround? Fortunately there is. I like the workaround described on the Python Tips website. To solve this issue, we can define a method similar to the following:

def jsonDefault(object):    

    return object.__dict__


Then encode the object into JSON as follows:

jsonAbder = json.dumps(abder, default=jsonDefault)


If you print jsonAbder, you should get the following output:

{"name": "Abder"}


We have now encoded a Python object (abder) into JSON.

Conclusion

From this tutorial, we can notice that Python again and again is proving not only its ability to work with different applications, but also its flexibility to work with different issues while working with an application, as we saw in the last part of the tutorial.

If you want to know more about the json module, you can visit the documentation page.

How to pull a random record using Django’s ORM?

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How to pull a random record using Django’s ORM?

original source: https://stackoverflow.com/questions/962619/how-to-pull-a-random-record-using-djangos-orm

Using order_by('?') will kill the db server on the second day in production. A better way is something like what is described in Getting a random row from a relational database.

from django.db.models.aggregates import Count
from random import randint

class PaintingManager(models.Manager):
    def random(self):
        count = self.aggregate(count=Count('id'))['count']
        random_index = randint(0, count - 1)
        return self.all()[random_index]

explain the way to access inner class in java?

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explain the way to access inner class in java?

original source : https://stackoverflow.com/questions/22866454/explain-the-way-to-access-inner-class-in-java

You’re actually accessing an inner class in a non-static way. A static inner class is actually different – the compiler makes a top-level class for it that is hidden from the programmer, which then works similarly to the way of instantiation that you have posted for the inner class.

You have to declare this way because since the inner class is non-static, it needs an instance of the outer class to make an instance of the inner class.

Outer o = new Outer();

is the required instance for the outer class.

Outer.Inner inner = o.new Inner();

is required for the instance of the inner class