Develop Reference

Android:Dynamically changing the height of the image view according to the received json data

I am accessing a mysql database table to show the tank level .I need to display the value in an image view using a rectangle.Each time value of the level changes I need to change the height of the rectangle.How is it possible in android.In the below code container 1 and container 2 is the variable which stores the level data.How to access this data and change the height of the image view.
package com.example.tg.mysmartcontainer;
import android.os.AsyncTask; import android.os.Bundle; import
android.support.v7.app.ActionBarActivity; import
android.widget.ListAdapter; import android.widget.ListView; import
android.widget.SimpleAdapter; import android.os.Handler; import
org.apache.http.HttpEntity; import org.apache.http.HttpResponse;
import org.apache.http.client.methods.HttpPost; import
org.apache.http.impl.client.DefaultHttpClient; import
org.apache.http.params.BasicHttpParams; import org.json.JSONArray;
import org.json.JSONException; import org.json.JSONObject;
import java.io.BufferedReader; import java.io.InputStream; import
java.io.InputStreamReader; import java.util.ArrayList; import
java.util.HashMap;
public class MainActivity extends ActionBarActivity {
String myJSON;
Handler mHandler;
private static final String TAG_RESULTS = "result";
private static final String TAG_timeStamp = "timeStamp";
private static final String TAG_container1 = "container1";
private static final String TAG_container2 = "container2";
JSONArray container = null;
ArrayList<HashMap<String, String>> ContainerList;
ListView list;
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
list = (ListView) findViewById(R.id.listView);
ContainerList = new ArrayList<HashMap<String, String>>();
final Handler handler = new Handler();
Runnable refresh = new Runnable() {
#Override
public void run() {
getData();
handler.postDelayed(this, 0);
}
};
handler.postDelayed(refresh, 0);
//getData();
}
public void getData() {
class GetDataJSON extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
DefaultHttpClient httpclient = new DefaultHttpClient(new BasicHttpParams());
HttpPost httppost = new HttpPost("http://smartgrocer.000webhostapp.com/get_data.php");
// Depends on your web service
httppost.setHeader("Content-type", "application/json");
InputStream inputStream = null;
String result = null;
try {
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
inputStream = entity.getContent();
// json is UTF-8 by default
BufferedReader reader = new BufferedReader(new InputStreamReader(inputStream, "UTF-8"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
result = sb.toString();
} catch (Exception e) {
// Oops
} finally {
try {
if (inputStream != null) inputStream.close();
} catch (Exception squish) {
}
}
return result;
}
#Override
protected void onPostExecute(String result) {
myJSON = result;
showList();
}
}
GetDataJSON g = new GetDataJSON();
g.execute();
}
protected void showList() {
try {
JSONObject jsonObj = new JSONObject(myJSON);
container = jsonObj.getJSONArray(TAG_RESULTS);
if(ContainerList!=null&&ContainerList.size()>0)
ContainerList.clear();
for (int i = 0; i < container.length(); i++) {
JSONObject c = container.getJSONObject(i);
String timeStamp = c.getString(TAG_timeStamp);
String container1 = c.getString(TAG_container1);
String container2 = c.getString(TAG_container2);
HashMap<String, String> container = new HashMap<String, String>();
container.put(TAG_timeStamp, timeStamp);
container.put(TAG_container1, container1);
container.put(TAG_container2, container2);
ContainerList.add(container);
}
ListAdapter adapter = new SimpleAdapter(
MainActivity.this, ContainerList, R.layout.list_item,
new String[]{TAG_timeStamp, TAG_container1, TAG_container2},
new int[]{R.id.timeStamp, R.id.container1, R.id.container2}
);
list.setAdapter(adapter);
} catch (JSONException e) {
e.printStackTrace();
}
}
}

to set the height of the ImageView:
image_view.getLayoutParams().height = 20;
Hope this helps.
Important. If you're setting the height after the layout has already been 'laid out', make sure you also call:
image_view.requestLayout()

Change the height of the imageView according to the current value :
tankImageView.setHeight((int)(currentValue / maxValue));

JSON parsing error - not parse in google API 4.1 jelly bean

i am working on an app using json parsing...in this parsing is done by json of the given url.
As i run my project on emulator having target = "Google APIs (Google Inc.) - API level 10"
then it runs properly and shows needed results from the target url.
but when run my project on emulator having target = "Google APIs (Google Inc.) - API level 16"
then it shows error and it never parse the given url data and get force close.
i want to make app which run on every API level.
please help...
here's my code:
json parser class:
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.io.UnsupportedEncodingException;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.util.Log;
public class JSONParser {
static InputStream is = null;
static JSONArray jObj = null;
static String json = "";
static String req = "POST";
// constructor
public JSONParser() {
}
public JSONArray getJSONFromUrl(String url, String method) {
// Making HTTP request
try {
// defaultHttpClient
DefaultHttpClient httpClient = new DefaultHttpClient();
HttpResponse httpResponse = null;
if(method == req) {
HttpPost httpC = new HttpPost(url);
httpResponse = httpClient.execute(httpC);
}else {
HttpGet httpC = new HttpGet(url);
httpResponse = httpClient.execute(httpC);
}
HttpEntity httpEntity = httpResponse.getEntity();
is = httpEntity.getContent();
} catch (UnsupportedEncodingException e) {
e.printStackTrace();
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
try {
BufferedReader reader = new BufferedReader(new InputStreamReader(
is, "iso-8859-1"), 8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
json = sb.toString();
} catch (Exception e) {
Log.e("Buffer Error", "Error converting result " + e.toString());
}
// try parse the string to a JSON object
try {
jObj = new JSONArray(json);
} catch (JSONException e) {
Log.e("JSON Parser", "Error parsing data " + e.toString());
}
// return JSON String
return jObj;
}
}
Another class using json parser class snd fetch data:
import java.util.ArrayList;
import java.util.HashMap;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.app.ListActivity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.SimpleAdapter;
public class showData extends ListActivity{
public static String url = "http://something/something/";
public static final String TAG_A = "a";
public static final String TAG_B = "b";
public static final String TAG_C = "c";
public static final String TAG_D = "d";
public static final String TAG_E = "e";
public static final String TAG_F = "f";
public static final String GET = "get";
JSONArray Data1 = null;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
ArrayList<HashMap<String, String>> contactList = new ArrayList<HashMap<String, String>>();
EditText editext_text = (EditText) findViewById(R.id.et);
String urlnew = url + editext_text.getText().toString();
Log.d("url", urlnew);
JSONParser jParser = new JSONParser();
// getting JSON string from URL
area1 = jParser.getJSONFromUrl(urlnew, GET);
Log.d("Json String", area1.toString());
try {
for(int i = 0; i < area1.length(); i++){
JSONObject c = area1.getJSONObject(i);
// Storing each json item in variable
String a = c.getString(TAG_A);
String b = c.getString(TAG_B);
String c = c.getString(TAG_C);
String d = c.getString(TAG_D);
String e = c.getString(TAG_E);
HashMap<String,String> map = new HashMap<String, String>();
// adding each child node to HashMap key => value
map.put(TAG_A, a);
map.put(TAG_B, b);
map.put(TAG_C, c);
map.put(TAG_D, d);
map.put(TAG_E, e);
// adding HashList to ArrayList
contactList.add(map);
}
} catch (JSONException e) {
e.printStackTrace();
}
ListAdapter adapter = new SimpleAdapter(this, contactList,
R.layout.list_item_area,
new String[] { TAG_B, TAG_A, TAG_C, TAG_D, TAG_E }, new int[] {
R.id.b, R.id.a, R.id.c, R.id.d, R.id.e });
setListAdapter(adapter);
}
}

You are getting a NetworkOnMainThreadException because as the name is self-explaining, you are doing network request on UI Thread that will make your application laggy and create an horrible experience.
The exception that is thrown when an application attempts to perform a
networking operation on its main thread.
This is only thrown for applications targeting the Honeycomb SDK or
higher. Applications targeting earlier SDK versions are allowed to do
networking on their main event loop threads, but it's heavily
discouraged. See the document Designing for Responsiveness.
You should use Threads or AsyncTask, do you need some explanations on how to use them?
private class NetworkTask extends AsyncTask<String, Void, String> {
#Override
protected String doInBackground(String... params) {
//DO YOUR STUFF
}
#Override
protected void onPostExecute(String result) {
//Update UI
}
#Override
protected void onPreExecute() {
}
#Override
protected void onProgressUpdate(Void... values) {
}
}

This is Network On Main Thread Exception, You have to use Thread for network connection, because the main thread is UI thread will not give any response for Network connection. Use separate thread for network connection

How to display a JSON from web service in Android List

I am trying since yesterday to make my application take some JSON data generated by a PHP file and then display this data in a list view.
The PHP File is encoding data using encode method:
echo json_encode($results);
Viewed from the browsers view source the JSON generated by file.php looks like this:
["","CSD1939","CSD1939"]
The JSONLint (A great tool) validates this as a correct JSON format.
When I am trying to use my application to fetch this JSON from the webservice I am fetching it as a String first but I am having trouble passing it to the adapter and making it display correctly.
I only managed until now to create a listview that displays a String Array.
What is the best way to fetch this JSON data and display it in the list.
package com.example.ams;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import java.util.HashMap;
import java.util.List;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.StatusLine;
import org.apache.http.client.ClientProtocolException;
import org.apache.http.client.HttpClient;
import org.apache.http.client.methods.HttpGet;
import org.apache.http.impl.client.DefaultHttpClient;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.annotation.SuppressLint;
import android.app.Activity;
import android.content.Context;
import android.os.AsyncTask;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
import android.widget.AdapterView;
import android.widget.ArrayAdapter;
import android.widget.ListView;
public class ViewClasses extends Activity {
#SuppressLint("NewApi")
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.view_classes);
new GetInfo().execute();
// ==============Functionality Start====================
// final ListView listview = (ListView) findViewById(R.id.listview);
}
private class GetInfo extends AsyncTask<Void, Void, String> {
protected String doInBackground(Void... params) {
// Fetch the JSON from the web and we pass it as a string to
// the ON POST EXECUTE method
StringBuilder builder = new StringBuilder();
HttpClient client = new DefaultHttpClient();
HttpGet httpGet = new HttpGet(
"file.php?get=XXX");
try {
HttpResponse response = client.execute(httpGet);
StatusLine statusLine = response.getStatusLine();
int statusCode = statusLine.getStatusCode();
if (statusCode == 200) {
HttpEntity entity = response.getEntity();
InputStream content = entity.getContent();
BufferedReader reader = new BufferedReader(
new InputStreamReader(content));
String line;
while ((line = reader.readLine()) != null) {
builder.append(line);
}
} else {
Log.e(this.toString(), "Failed to download file");
}
} catch (ClientProtocolException e) {
e.printStackTrace();
} catch (IOException e) {
e.printStackTrace();
}
return builder.toString();
}
protected void onPostExecute(String result) {
// Here it should turn it into a JSON and then display it in a list.
// Gets the list view
final ListView listview = (ListView) findViewById(R.id.listview);
// Converts the String to a JSON array
System.out.println(result);
JSONArray jsonArray;
try {
System.out.println(result);
jsonArray = new JSONArray(result);
Log.i(ViewClasses.class.getName(), "Number of entries "
+ jsonArray.length());
for (int i = 0; i < jsonArray.length(); i++) {
JSONObject jsonObject = jsonArray.getJSONObject(i);
Log.i(ViewClasses.class.getName(),
jsonObject.getString("text"));
// Converts JSON array to Java Array
final ArrayList<String> list = new ArrayList<String>();
// values instead of jsonArray
if (jsonArray != null) {
int len = jsonArray.length();
for (int i1 = 0; i1 < len; i1++) {
list.add(jsonArray.get(i).toString());
}
}
final StableArrayAdapter adapter = new StableArrayAdapter(
getApplicationContext(),
android.R.layout.simple_list_item_1, list);
listview.setAdapter(adapter);
}
} catch (JSONException e) {
// TODO Auto-generated catch block
e.printStackTrace();
}
}
}
private class StableArrayAdapter extends ArrayAdapter<String> {
HashMap<String, Integer> mIdMap = new HashMap<String, Integer>();
public StableArrayAdapter(Context context, int textViewResourceId,
List<String> objects) {
super(context, textViewResourceId, objects);
for (int i = 0; i < objects.size(); ++i) {
mIdMap.put(objects.get(i), i);
}
}
#Override
public long getItemId(int position) {
String item = getItem(position);
return mIdMap.get(item);
}
#Override
public boolean hasStableIds() {
return true;
}
}
}
My Layout XML file looks like this
<ListView xmlns:android="http://schemas.android.com/apk/res/android"
android:id="#+id/listview"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
Running this code I am getting a blank screen.
Any help, pointers, hints would be greatly appreciated

It is just returning JSONArray with Strings, so you should not create JSONObject from it.
JSONObject jsonObject = jsonArray.getJSONObject(i);
this will cause Exception as JSONArray doesn't contain JSONObjects.
So parse like this
ArrayList<String> list = new ArrayList<String>();
for (int i = 0; i < jsonArray.length(); i++) {
list.add(jsonArray.get(i).toString());
}

using AsyncTask i want the data in list view when calling restful api

I just build a demo application through async task and now i want the json data in list view so i dont know where i can add json functions and array list etc so plz guide me or help me by edit the code i thankful in advance and plz help im new to android and java
package your.packag.namespace;
import java.io.IOException;
import java.io.InputStream;
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.protocol.BasicHttpContext;
import org.apache.http.protocol.HttpContext;
import android.app.Activity;
import android.os.AsyncTask;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;
import android.widget.EditText;
public class runActivity extends Activity implements OnClickListener {
#Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
findViewById(R.id.my_button).setOnClickListener(this);
}
#Override
public void onClick(View arg0) {
Button b = (Button)findViewById(R.id.my_button);
b.setClickable(false);
new LongRunningGetIO().execute();
}
private class LongRunningGetIO extends AsyncTask <Void, Void, String> {
protected String getASCIIContentFromEntity(HttpEntity entity) throws IllegalStateException, IOException {
InputStream in = entity.getContent();
StringBuffer out = new StringBuffer();
int n = 1;
while (n>0) {
byte[] b = new byte[4096];
n = in.read(b);
if (n>0) out.append(new String(b, 0, n));
}
return out.toString();
}
#Override
protected String doInBackground(Void... params) {
HttpClient httpClient = new DefaultHttpClient();
HttpContext localContext = new BasicHttpContext();
HttpGet httpGet = new HttpGet("http://192.168.1.156/recess/document/document");
HttpClient client = new DefaultHttpClient();
HttpResponse response=null;
try{
response = client.execute(httpGet);}
catch(Exception e){}
System.out.println(response.getStatusLine());
String text = null;
try {
response = httpClient.execute(httpGet, localContext);
HttpEntity entity = response.getEntity();
text = getASCIIContentFromEntity(entity);
} catch (Exception e) {
return e.getLocalizedMessage();
}
return text;
}
protected void onPostExecute(String results) {
if (results!=null) {
EditText et = (EditText)findViewById(R.id.my_edit);
et.setText(results);
}
Button b = (Button)findViewById(R.id.my_button);
b.setClickable(true);
}
}}

You can use the built-in org.json classes to convert the retrieved string (your text variable content) in to JSON objects.
Have a look at the tutorial from Lars Vogel on how to do that.

Populate list view

I am developing a final year project and I am stuck at a point. I have to retrieve names of doctors from my database (MySQL database) and show it in a list view. I was able to establish a connection with the server and retrieve values, but when I tried to show the values in a list view, the application crashed!
I tried the same example given in [Hello, Views, List View][4].
It works for a predefined array like
private String lv_arr[]={"Android","iPhone","BlackBerry","AndroidPeople"};
but for a string array retrieved from the database it shows a run time exception. Is there any way I can achieve this?
package com.proj;
import java.io.BufferedReader;
import java.io.InputStream;
import java.io.InputStreamReader;
import java.util.ArrayList;
import org.apache.http.HttpEntity;
import org.apache.http.HttpResponse;
import org.apache.http.NameValuePair;
import org.apache.http.client.HttpClient;
import org.apache.http.client.entity.UrlEncodedFormEntity;
import org.apache.http.client.methods.HttpPost;
import org.apache.http.impl.client.DefaultHttpClient;
import org.apache.http.message.BasicNameValuePair;
import org.json.JSONArray;
import org.json.JSONException;
import org.json.JSONObject;
import android.widget.*;
import android.app.ListActivity;
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.util.Log;
import android.widget.LinearLayout;
import android.widget.TextView;
public class proj extends ListActivity {
/** Called when the activity is first created. */
public int n=0;
public int t=0;
public int i=0;
public String name[]=new String[30];
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Create a crude view - this should really be set via the layout resources
// but since its an example saves declaring them in the XML.
TextView txt=(TextView)findViewById(R.id.tv);;
//Call the method to run the data retrieval
getServerData(KEY_121);
setListAdapter(new ArrayAdapter(this,
android.R.layout.simple_list_item_1, name));
}
public static final String KEY_121 = "http://10.0.2.2/doc.php"; //I use my real IP address here.
private String getServerData(String returnString) {
InputStream is = null;
String result = "";
//The year data to send.
ArrayList<NameValuePair> nameValuePairs = new ArrayList<NameValuePair>();
nameValuePairs.add(new BasicNameValuePair("year","1970"));
//HTTP post
try{
HttpClient httpclient = new DefaultHttpClient();
HttpPost httppost = new HttpPost(KEY_121);
httppost.setEntity(new UrlEncodedFormEntity(nameValuePairs));
HttpResponse response = httpclient.execute(httppost);
HttpEntity entity = response.getEntity();
is = entity.getContent();
}
catch(Exception e){
Log.e("log_tag", "Error in http connection "+e.toString());
}
//Convert response to string
try{
BufferedReader reader = new BufferedReader(new InputStreamReader(is,"iso-8859-1"),8);
StringBuilder sb = new StringBuilder();
String line = null;
while ((line = reader.readLine()) != null) {
sb.append(line + "\n");
}
is.close();
result=sb.toString();
}
catch(Exception e){
Log.e("log_tag", "Error converting result "+e.toString());
}
//Parse JSON data
try {
JSONArray jArray = new JSONArray(result);
for(i=0;i<jArray.length();i++)
{
JSONObject json_data = jArray.getJSONObject(i);
n=jArray.length();
name[i]=json_data.getString("name");
//Get an output to the screen
returnString += "\n\t" + jArray.getJSONObject(i);
}
}
catch(JSONException e)
{
Log.e("log_tag", "Error parsing data "+e.toString());
e.printStackTrace();
}
return returnString;
}
}

You are using
1.)
android:id="#+id/list"
inside the ListView, but if your extend an activity by ListActivity you have to use
android:id = "#android:id/list"
2.)
You return a String[] here, not String
private String[] getServerData(String returnString) {
.......
JSONArray jArray = new JSONArray(result);
name = new String[jArray.length()];
for(i=0;i<jArray.length();i++)
{
JSONObject json_data = jArray.getJSONObject(i);
name[i]=json_data.getString("name");
}
return name;
}
And in ArrayAdapter, do it like this:
ArrayAdapter<String> adapter = new ArrayAdapter<String>(this, android.R.layout.simple_list_item_1, getServerData(KEY_121));
setListAdapter(adapter);

public String name[];
#Override
public void onCreate(Bundle savedInstanceState)
{
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
// Create a crude view - this should really be set via the layout resources
// but since its an example saves declaring them in the XML.
TextView txt=(TextView)findViewById(R.id.tv);;
...
...
try {
JSONArray jArray = new JSONArray(result);
name[]=new String[jArray.length()];
for(i=0;i<jArray.length();i++)
{
JSONObject json_data = jArray.getJSONObject(i);
n=jArray.length();
name[i]=json_data.getString("name");
//Get an output to the screen
returnString += "\n\t" + jArray.getJSONObject(i);
}
}
catch(JSONException e)
{
Log.e("log_tag", "Error parsing data "+e.toString());
e.printStackTrace();
}
It seems that initializing name[] with a size of 30 may be too small.