Example on Dynamic ListActivity in Android

ListActivity is an important element of android apps. ListActivity manages all data in linear format.. on user screen.

Here is simple example based on how to use ListActivity. 

It is a demo, which express how to add data in list with every hit on  Add button & remove last entry data with Remove button hit.

1) Create an android project in eclipse. 

2) extends your MainActivity with ListActivity.

3) design your main.xml file, in such way that ,

          At top you will having one edit text ,so you put data on it.. & two Button, Add & Remove. & below of it.. one ListView to show data .

4) so,your  main.xml will be look like ,follow

here, activtiy_dynamic_list.xml is mine xml file.. 

******************************************************

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

    <LinearLayout

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:orientation="horizontal"

        android:weightSum="100" >

        <EditText

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_weight="50" 

            android:id="@+id/editText"/>

        <Button

            android:id="@+id/add"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_weight="25"

            android:text="Add data" />

        <Button

            android:id="@+id/clear"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_weight="25"

            android:text="Delete data" />

    </LinearLayout>

    

        <ListView

            android:id="@android:id/list"

            android:layout_width="match_parent"

            android:layout_height="match_parent"

            android:drawSelectorOnTop="false" />

</LinearLayout>

******************************************************

******************************************************************

package com.examples.dynamiclist;

import java.util.ArrayList;

import java.util.List;

import android.app.ListActivity;

import android.content.Context;

import android.os.Bundle;

import android.view.LayoutInflater;

import android.view.Menu;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.Button;

import android.widget.EditText;

import android.widget.TextView;

public class DynamicList extends ListActivity {

MyDataAdapter adapters;

ArrayList<String> st;

Button add, remove;

TextView tv;

EditText editText;

ArrayAdapter<String> adapter;

String obj;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.activity_dynamic_list);

add = (Button) findViewById(R.id.add);

remove = (Button) findViewById(R.id.clear);

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

st = new ArrayList<String>();

st.add("India");

st.add("USA");

// adapter = new ArrayAdapter<String>(this, R.layout.myrow,

// R.id.myrowdata, st);

adapters = new MyDataAdapter(this, R.layout.myrow, R.id.myrowdata, st);

setListAdapter(adapters);

add.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

// TODO Auto-generated method stub

obj = editText.getText().toString();

st.add(obj);

adapters.notifyDataSetChanged();

}

});

}

@Override

public boolean onCreateOptionsMenu(Menu menu) {

getMenuInflater().inflate(R.menu.activity_dynamic_list, menu);

return true;

}

public class MyDataAdapter extends ArrayAdapter<String> {

public MyDataAdapter(Context context, int resource, int textViewResourceId, List<String> objects) {

super(context, resource, textViewResourceId, objects);

// TODO Auto-generated constructor stub

}

@Override

public View getView(final int position, View convertView, ViewGroup parent) {

// TODO Auto-generated method stub

LayoutInflater inflater = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

View view = inflater.inflate(R.layout.myrow, null);

tv = (TextView) view.findViewById(R.id.myrowdata);

tv.setText(st.get(position));

remove.setOnClickListener(new View.OnClickListener() {

public void onClick(View v) {

// TODO Auto-generated method stub

//st.clear();

st.remove(position);

adapters.notifyDataSetChanged();

}

});

return view;

}

}

}

******************************************************************

 & output will be look like,

Fig 1. user screen 

Fig 2. Adding Data 

Fig 3. showing data in list

Fig 4. removing data

These,is simple demo for dynamic view with ListActivity 

   Regards :) ,Happy Coding 

Example On ListActivity With showing twits from twitter by using JSON

Hello Friends Today, I'l share my few knowledge about android & its concepts.

Today , i am gonna tell how to use ListActivity, JSON data, AQuery in android app.So,lets get started

As i told you above ,ListActivity..... as it name suggest above.. it shows all your data in list view manner... but question is how data is come to u .. so we need to specify adapter for your list.. as it way... it manages data.in user screen. 

* What is JSON Data ?

JSON (JavaScript Object Notation) is an independent data exchange format. It is limited to text and numeric values. Binary values are not supported.

                      JSON is a subset of the JavaScript Specification (ECME-Script) and it is therefore directly supported in JavaScript.

Data structures in JSON are based on key / value pairs. The key is a string, the value can be a numerical value, a boolean value (true or false) or an object.

                    An JSON object is a set of key / value pairs which starts with "{" and ends with "}".

example----

{
 firstName:'Sushant',
 lastName:'Patekar',
 address: {
   Street:'Achole Street.',
   number: '304'
 }
} 

How To View Json Data------- 

if you want view json data from url......... just put that link on any browser ,

here we have link is.. for our app..

http://search.twitter.com/search.json?q=@Android

collect data. & put it data.... on the free space of these link

then,click on Format & You will get availible your json data

Here, we trying to fetch posts of different user relates to "Android" on twitter.

its simple.

while playing with ListActivity, you have to take care of these below things,

>> extends Your class with ListActivity(--------not With Activity------------)

                             * as we know now,when we extending our activity we need to set desirable view as layout in OnCreate()... by using setContentView(R.layout.main).

            but, in ListActivity we need Adapter.. for specifying lookup of your ListActivity. 

   where,Adapter is use for different types with different purpose in android app. here we use arrayadapter to design our row for list.that will be done by simple layout .xml file.

                               * Difference between ListView & ListActivity... 

                   ListView is UI componet which will added layout .xml files. we have to spcify id for it in xml file . & then in .java class ,

                     ListView myListView=(ListView) findViewById(R.id.listview1);

                     myListView.setAdapter(myNewAdapter);

          But, in ListView code will just Simply changes as,

 extends your class with ListActivity

 create adapter for (row) for it... & then 

                          setListAdapter(myNewAdapter);

>> create An .xml file which will specifying view for adapter.. 

here, i am supposed to show user profile pic, with his name & his tweet.. so i need one imageview, & two textview ,so my .xml will look like .......

------------------------list_item.xml------------------------------------

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:gravity="left|center"

    android:paddingBottom="5px"

    android:paddingLeft="5px"

    android:paddingTop="5px" >

    <ImageView

        android:id="@+id/avatar"

        android:layout_width="wrap_content"

        android:layout_height="fill_parent"

        android:layout_marginRight="6dip"

        android:src="@drawable/ic_launcher" />

    <LinearLayout

        android:layout_width="0dip"

        android:layout_height="fill_parent"

        android:layout_weight="1"

        android:orientation="vertical" >

        <TextView

            android:id="@+id/username"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:gravity="center"

            android:textSize="15dp"

            android:textStyle="bold" />

        <TextView

            android:id="@+id/message"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_marginLeft="10px"

            android:textColor="#0099CC" />

        <TextView

            android:id="@+id/time"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="" >

        </TextView>

    </LinearLayout>

</LinearLayout>

& now our layout is ready... but have you know that we wil going to play with lots of data ... here, i mean.. we will fetching each users tweet.. with his name,& profile-pic via.. Internet... so if we write code for it .. onCreate() ... so our app will crash ...  so for make it comfort we will all these stuff from background thread by using AsyncTask<> . AsyncTask is use to perform background task along ur app & onCreate method.. without disturbing it.

so..untill,its clear that.. will pulling data by using AsyncTask & put in on List by using ArrayAdapter... but.. while pulling tweets,& user name.. we will not having issue... but at the time of pulling image.. over Internet.. it causes time consuming.. & which results rough scrolling appearance.. for list items.

to avoid it, we use Aquery....

What is Aquery?

Android-Query (AQuery) is a light-weight library for doing asynchronous tasks and manipulating UI elements in Android. its simple to use it.. just download these library ,from here, & add it as library to your project.

>> Inside Class  we will using AsyncTask & then pulling data using JSON. 

so our full code will look like as below,

----------------------------- Twits.java---------------------------------

package com.examples.Twits;

import java.net.URI;

import java.net.URL;

import java.util.ArrayList;

import org.apache.http.HttpEntity;

import org.apache.http.HttpResponse;

import org.apache.http.client.HttpClient;

import org.apache.http.client.methods.HttpGet;

import org.apache.http.impl.client.DefaultHttpClient;

import org.apache.http.util.EntityUtils;

import org.json.JSONArray;

import org.json.JSONException;

import org.json.JSONObject;

import android.app.ListActivity;

import android.app.ProgressDialog;

import android.content.Context;

import android.graphics.Bitmap;

import android.graphics.BitmapFactory;

import android.os.AsyncTask;

import android.os.Bundle;

import android.os.Handler;

import android.os.Message;

import android.os.SystemClock;

import android.util.Log;

import android.view.LayoutInflater;

import android.view.View;

import android.view.ViewGroup;

import android.widget.ArrayAdapter;

import android.widget.ImageView;

import android.widget.ListView;

import android.widget.TextView;

import com.androidquery.AQuery;

import com.examples.Twits.Twits.myAsyncs.CustomAdapter;

public class Twits extends ListActivity {

HttpClient client;

ListView listview;

String widget_data, profile_Img_url;

ArrayList<TwitsModel> listItems;

ProgressDialog progressDialog;

ImageView img;

JSONObject newJsonObject;

JSONObject jsonObject;

TextView username, message, time;

ImageView image;

AQuery aq;

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

aq = new AQuery(this);

new myAsyncs().execute();

// TODO Auto-generated method stub

}

public class myAsyncs extends AsyncTask<String, Integer, ArrayList<TwitsModel>> {

int progress_status;

@Override

protected void onPreExecute() {

super.onPreExecute();

progressDialog = new ProgressDialog(Twits.this);

progressDialog.setCancelable(true);

progressDialog.setMessage("Loading...");

progressDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);

progressDialog.setMax(100);

progressDialog.show();

progress_status = 0;

}

@Override

protected ArrayList<TwitsModel> doInBackground(String... params) {

listItems = new ArrayList<TwitsModel>();

client = new DefaultHttpClient();

while (progress_status < 100) {

progress_status += 1;

publishProgress(progress_status);

}

try {

URI website1 = new URI("http://search.twitter.com/search.json?q=@Android");

HttpClient client = new DefaultHttpClient();

HttpGet request = new HttpGet();

request.setURI(website1);

HttpResponse response = client.execute(request);

HttpEntity entity = response.getEntity();

String str = EntityUtils.toString(entity);

newJsonObject = new JSONObject(str);

try {

JSONArray JsonArrayForResult = newJsonObject.getJSONArray("results");

for (int i = 0; i < JsonArrayForResult.length(); i++) {

jsonObject = JsonArrayForResult.getJSONObject(i);

listItems.add(new TwitsModel(jsonObject));

}

} catch (JSONException e) {

e.printStackTrace();

}

} catch (Exception e) {

Log.e("log_tag", "Error in http connection: " + e.toString());

}

return listItems;

}

@Override

protected void onPostExecute(ArrayList<TwitsModel> result) {

super.onPostExecute(result);

Message message = new Message();

handler.sendMessage(message);

}

private Handler handler = new Handler() {

@Override

public void handleMessage(Message msg) {

super.handleMessage(msg);

CustomAdapter myAdapter = new CustomAdapter(getApplicationContext(), R.layout.list_item, listItems);

setListAdapter(myAdapter);

progressDialog.dismiss();

myAdapter.setNotifyOnChange(true);

}

};

class CustomAdapter extends ArrayAdapter<TwitsModel> {

ArrayList<TwitsModel> C_list;

public CustomAdapter(Context context, int textViewResourceId, ArrayList<TwitsModel> tweets) {

super(context, textViewResourceId, tweets);

this.C_list = tweets;

}

public View getView(int position, View convertView, ViewGroup parent) {

View v = convertView;

aq = new AQuery(v);

if (v == null) {

LayoutInflater vi = (LayoutInflater) getSystemService(Context.LAYOUT_INFLATER_SERVICE);

v = vi.inflate(R.layout.list_item, null);

username = (TextView) v.findViewById(R.id.username);

message = (TextView) v.findViewById(R.id.message);

image = (ImageView) v.findViewById(R.id.avatar);

time = (TextView) v.findViewById(R.id.time);

}

TwitsModel tweet = C_list.get(position);

if (tweet != null) {

if (username != null) {

username.setText(tweet.name);

}

if (message != null) {

message.setText(tweet.twit);

}

aq.recycle(v);

aq.id(R.id.avatar).image(tweet.imageUrl, false, true);

if (time != null) {

time.setText(tweet.time1);

}

}

return v;

// end of getView

}

}

@Override

protected void onCancelled() {

super.onCancelled();

}

@Override

protected void onProgressUpdate(Integer... values) {

super.onProgressUpdate(values);

progressDialog.setProgress(values[0]);

}

}

}

------------------------------------------------------------------------------------------

we require one class here for fetching JSON data ,which willl be like as,

-------------------------------------TwitsModel.java------------------------------

package com.examples.Twits;

import java.util.Date;

import org.json.JSONException;

import org.json.JSONObject;

public class TwitsModel {

public String name;

public String imageUrl;

public String twit;

public String time, time1;

Date date;

public TwitsModel(JSONObject jObject) {

try {

name = jObject.getString("from_user");

time = jObject.getString("created_at");

twit = jObject.getString("text");

imageUrl = jObject.getString("profile_image_url");

}

catch (JSONException e) {

e.printStackTrace();

}

}

}

----------------------------------------------------------------------------------------

& inside  list_item.xml 

<?xml version="1.0" encoding="utf-8"?>

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    android:layout_width="wrap_content"

    android:layout_height="wrap_content"

    android:gravity="left|center"

    android:paddingBottom="5px"

    android:paddingLeft="5px"

    android:paddingTop="5px" >

    <ImageView

        android:id="@+id/avatar"

        android:layout_width="wrap_content"

        android:layout_height="fill_parent"

        android:layout_marginRight="6dip"

        android:src="@drawable/ic_launcher" />

    <LinearLayout

        android:layout_width="0dip"

        android:layout_height="fill_parent"

        android:layout_weight="1"

        android:orientation="vertical" >

        <TextView

            android:id="@+id/username"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:gravity="center"

            android:textSize="15dp"

            android:textStyle="bold" />

        <TextView

            android:id="@+id/message"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:layout_marginLeft="10px"

            android:textColor="#0099CC" />

        <TextView

            android:id="@+id/time"

            android:layout_width="wrap_content"

            android:layout_height="wrap_content"

            android:text="" >

        </TextView>

    </LinearLayout>

</LinearLayout>

------------------------------------------------------------------------------------------

& inside AndroidManifest.xml file,

 Specifey Internet permission ....................like ,

<uses-permission android:name="android.permission.INTERNET"/>

---------------------------------------------------------------------------------------

& Your code is now ready to compile.............& hit on Run Application,

output will look like...........

fig - AsyncTask 

fig-Twits in List

Finally,Happy Coding :) 

Example On Download Manager

Android has introduced new class to work on download mechanism. "Download Manager" class has been added at API level 9.  

Today,  i will tell you how to use download manager class functionality in our android app. traditionally we used  Http with Inputstream/outputstream for downloading any data in android app.

for using Download Manager in app, we have to learn its subclasses & its respective mehods.....

Download Manager having two classes, 

1) DownloadManager.Query 

        It helps to filter dowload manaer queries.which means it fires download related queries.& gives  results on it,like how much download has completed, downloaded file exist ... n many more....

2) DownloadManger.Request 

               It helps to create new Download Request.with these class we can specify what to downlod,where to put downloaded file on ... n many more 

Lets create an app.....................

1) create an project with name of DownloadDataActivity(Here i used,these name)

2)build target above -android api 14 (above 9)

lets code, together

after creating project.. lets first modified our layout ....

as we know we are going to download data (here we take an image).

so we need one button on our layout , when we hit on it ,.... certain download related event get fired & download get started.

so , inside on 

******************* main.xml **************************

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"

    xmlns:tools="http://schemas.android.com/tools"

    android:layout_width="match_parent"

    android:layout_height="match_parent"

    android:orientation="vertical" >

> 

    <Button

        android:id="@+id/startDownload"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="Start Downloading my File" />

    <Button

        android:id="@+id/displayDownload"

        android:layout_width="match_parent"

        android:layout_height="wrap_content"

        android:text="Display all Downloads" />

   

</LinearLayout>

we used one button over here,for starting downloading data.

& inside Android Manifest.xml

we need to declare these uses-permission 

<uses-permission android:name="android.permission.INTERNET" />

    <uses-permission android:name="android.permission.ACCESS_NETWORK_STATE" />

    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />

Inside DownlodDataActivity.java 

we simply want to create event for start dowload button which can initiate download with respect to querry. 

so code will be looks like .... 

**********************DownloadDataActivity.java*************

first we need to assign few varible which we variable that we can use in our code further,

DownloadManager downloadManager;

Reqest request;

long downloadReference;

then in ,oncreate code will be look like,

@Override

        public void onCreate(Bundle savedInstanceState) {

                super.onCreate(savedInstanceState);

                downloadManager = (DownloadManager) getSystemService(DOWNLOAD_SERVICE);

       

                setContentView(R.layout.activity_download_data);

                 Button startDownload = (Button)                            findViewById(R.id.startDownload);

startDownload .setOnclicklistener(new View.OnClickListener() {

               

                @Override

                public void onClick(View v) {

               

                       

                }

        });

   

then, inside click event , 

we have to assign 

here we have to fire querry for downloding queery by using following 

request = new Request(Uri.parse("http://mirror-us-ga1.gallery.hd.org/_exhibits/natural-science/_more2002/_more04/pelicans-enjoying-water-sprinkler-on-lawn-2-MB.jpg"));

downloadReference = downloadManager.enqueue(request);

Where, downloadReference is long variable ,which  helps to download with help of function of enqueue.