Android and iOs tips

Question

In Android ViewGroup inherits from View. A ViewGroup is a container which holds Views.


ViewGroup (LinearLayout)
View (TextView)

Why did folks at Android defined this relationship as Inheritance instead of composition. As the ViewGroup contains Views shouldn't it be composition ?

Accepted Answer · 2011-12-23 06:12:43Z

I think you're getting too hung up on the wording.

A "ViewGroup" has every bit as much reason to inherit from a "View" as a "TextView", and "ImageView" or ... more to the point ... a "ScrollView" or a "SurfaceView" (the latter two both "contain things").

Perhaps "View" wasn't necessarily the best choice of terms ... but the class heirarchy makes complete sense. Regardless of what it's subclasses are named :)

IMHO ...

Answer 2 · 2011-12-23 06:53:08Z

Viewgroup inherits properties of views and does more with other views and viewgroup

Answer 3 · 2013-05-20 13:03:08Z

I think this is a great example of the Composite design pattern:

http://en.wikipedia.org/wiki/Composite_pattern

Even though the naming might not be the best...

Answer 4 · 2013-05-20 13:04:02Z

editText = (EditText)layout.findViewById(R.id.editText);


        editText.setOnEditorActionListener(new TextView.OnEditorActionListener() {

            @Override
            public boolean onEditorAction(TextView v, int actionId, KeyEvent event) {

                return false;
            }
        });

Answer 5 · 2013-05-20 13:05:04Z

That is upto user. When user sets your app as default browser, it will be default untill he changes it.

Accepted Answer · 2013-04-11 13:14:42Z

You could use a Map from String to your object type (I used Obj in order to make a SSCCE).

Assume we are given a list objects and a list strings.

Steps:

Put all objects in a map with their str variable as key

Get all those str variables using map.keySet()

Get all strings that are in objects but not in strings by keys.removeAll(strings)

Get all strings that are in strings but not in objects by strings.removeAll(keys)

Get the objects that correspond to the remaining keys

Note that you need to be careful in steps 3 and 4, because you need to back up one of the collections.


import java.util.*;

public class Test { 
    public static void main(String[] args) throws Exception {
        new Test();
    }

    public Test() {
        List objects = new ArrayList<>();
        objects.add(new Obj("a"));
        objects.add(new Obj("b"));
        objects.add(new Obj("c"));

        List strings = new ArrayList<>();
        strings.add("a");
        strings.add("d");
        strings.add("e");

        remove(objects, strings);

        System.out.println(objects);
        System.out.println(strings);
    }

    public void remove(List objects, List strings) {
        Map map = new HashMap<>();
        for (Obj object : objects) {
            map.put(object.str, object);
        }

        Set keys = map.keySet();
        List oldStrings = new ArrayList<>(strings);

        strings.removeAll(keys);
        keys.removeAll(oldStrings);

        objects.clear();
        for (String key: keys) {
            objects.add(map.get(key));
        }       
    }

    public class Obj {  
        public String str;
        public Obj(String str) {
            this.str = str;
        }
        @Override
        public String toString() {
            return str;
        }       
    }
}

Prints:


[b, c]
[d, e]

Answer 7 · 2013-04-11 13:11:34Z

Rough Java code:


HashSet commonKeys = new HashSet();
for (Share share : shares) {
    commonKeys.add(share.filePath);
}
commonKeys.retainAll(filePaths);
for (Iterator it = shares.iterator(); it.hasNext(); ) {
    Share share = it.next();
    if (commonKeys.contains(share.filePath)) {
        it.remove();
    }
}
filePaths.removeAll(commonKeys);

This won't be O(N) because remove on an ArrayList is expensive. To get O(N) behavior you either need to create new ArrayList instances, or add the elements you don't want removed to temporary lists, and then clear() and add them back into the original lists.

Answer 8 · 2013-04-11 13:29:57Z

I will go with some clues for you

Suppose you have two lists one for bean objects namely myBeans and another for filePaths namely filePaths


List beansToRemove = new ArrayList();
List filePathsToRemove = new ArrayList();

for(Bean myBean : myBeans) {
    for(FilePath filePath : filePaths) {
        if(myBean.getfilePath.equals(filePath.getFilePath())) {
            beansToRemove.add(myBean);
            filePathsToRemove.add(filePath);
        }
    }
}

//Now remove filePaths and beans if any

for(Bean myBean : beansToRemove) {
    myBeans.remove(myBean);
}

for(FilePath filePath : filePathsToRemove) {
    filePaths.remove(filePath);
}

it is just a flow to make you clear for what to do; you can further customize it according to your needs.

Er. Nikhil Agrawal · Answer 9 · 2013-04-11 13:07:41Z

You can use an outer loop to scan over the Bean objects, and an inner loop to scan over the file paths.

pseudo code:


for (Bean i in beans) {
    for (String p in paths) {
        if (i.path.equals(p)) {
            beansToRemove.add(i);
            pathsToRemove.add(p);
        }
    }
}
beans.removeAll(beansToRemove);
paths.removeAll(pathsToRemove);

I'm not sure if my extra arraylists to track the removed arraylists go against your question or not since the original arrays remain. If you presort both arrays on the path and keep track of the position in each area (not exhaustive search) you can improve it from n2 to nlgn

Android and iOs tips

Monday, May 20, 2013

[General] Google Hangout Contact Picture Incorrect

[General] Can't access playstore

[General] Can a 4G Network Smart Phone Plan Provide Internet Connection to a Desktop PC?

[General] Google Now Widget

[General] Android cant log in to google

[General] Site support email address

[android help] Android View and ViewGroup

[android help] How to catch Android soft keyboard next button event

[android help] Android NullPointerException on onCreateOptionsMenu

[android help] Webview App as default browser

[android help] Removing common elements between two different Arraylist

[android help] How to get the number of the largest value in a string

Google Voice on T-Mobile? [General]

Blogroll