Develop Reference

Android Activity to WebView and WebView to Activity Parameter Passing

I have an application in which an activity communicates with our server and gets the outstanding amount details. I want users to pay the outstanding amount using a payment gateway. for Payment Gateway, I have to call web page from webview and transfer outstanding amount details and other credentials from activity to the page loaded in webview. At the end of transaction I once again need to get some parameters back from webpage in webview to activity.
This is a two way communication which I want to achieve between an activity and a page loaded in webview. I tried to find out a way to do it but could not find a simple example which does such exchange.

You could achieve what you want using a javascript WebAppInterface as demonstrated here.
The main concept is that, you create a javascript interface inside the Activity holding your WebView.
private class WebPayInterface {
int amount;
boolean success;
#JavascriptInterface
public void PaymentFinished(int amount, boolean success) {
this.amount = amount;
this.success = success;
// do whatever you want in the parent activity.
}
}
Add the interface to your webView
webView.addJavascriptInterface(new WebPayInterface(), "WebPayInterface");
Finally in your html code using javascript you can call
WebPayInterface.PaymentFinished(100, true);

You can make use of Intent.putExtra() while navigating using Intents, Shared Preferences and also Bundle. Please read Android documentation for Shared Preferences, Intents, Bundle

Android: setImgVisibility() error

In my app I have a header with icon hidden, I have a adapter with a listview when I click the listview I go to a login screen using listener, when the login is successful is should come back to listview(adapter) and icon should get visible on header.
In the login activity I have the following code:
public void onClick(View v) {
String password = etPassword.getText().toString();
if(password.equals("guest")){
SearchAdapter.setImgVisibility();
} else {
//-----
}
finish();
}
In my adapter I am calling the setImgVisibility() as follows, but it is not working
public static void setImgVisibility() {
img.setVisibility(View.VISIBLE);
}
I am getting a Nullpointerexception near the line img.setVisibility(View.VISIBLE);
I am stuck here and don't know what I am doing wrong. Any suggestions or help is appreciated

I would imagine that img is null. You need to look at where this value is set and make sure happens before you call the method setImgVisibility.
Show more of your complete code for people to help further.
Additionally, i've just noticed you've used a static reference to your search adapter, you should be really careful using statics, especially where any referencing of images is concerned as images can be bound to the context, as such unless you nullify the static you will end up with a memory leak. (this used to be an old problem, not sure its still valid, but i would still avoid using a static reference).
Without more code we're not likely to be able to properly help you. For example are you switching activities when logging in? If you are, this won't work at all.
[given the comment below] If you switch activities then your activity containing the list view is going to be destroyed and then rebuilt then you navigate back to it. or it will at least go through the activity lifecycle. This means you can set the icon during the instantiation of the header img.
You could store your logged in state as a property of the Application or a preference. Grab this value when you set the header image and set the image accordingly.

your img object is null. Is your img object is same as View v then you can pass v in setImgVisibility() and then set v.setVisibility(View.VISIBLE)

Passing control from html to android to call an android method

I am a total newbie at android (as well as this is my first post on StackOverflow) and I was wondering if there is a way of passing control from a web view displaying HTML to the actual android code. To make it a little more clear:
Suppose I have a HTML code that I am displaying in the web view in android, now I click the submit button (which is in the HTML page), is there a way to use that click to call a method in the android code?
A very high level view can be something like
if(Submit is clicked){ //submit would be the submit button in the html page
call xyz(); //xyz would be the android method
}
I would really appreciate it if you guys can help.

It is possible, refer to this.
There is a simple example there that should kick you off.
Javascript is the word of the day.

Use addJavaScriptInterface() to put a reference in the Javascript environment to some Java object.
Here is a sample application demonstrating this, to allow a page in a WebView to retrieve a location from the activity hosting the WebView.

You can use WebView addJavascriptInterface to export your method to the HTML page, here is a relevant snippet:
WebViewVariable.addJavascriptInterface(new MyJavaScriptInterface(context), "Android");
Here is the code for MyJavaScriptInterface :
class MyJavaScriptInterface {
Context localContext;
public MyJavaScriptInterface(Context ctx) {
localContext = ctx;
}
public void pageReady() {
// do your work here
}
}
You can now call the above class's method pageReady() from your HTML page like this Android.pageReady(). Remember though that you can only pass primitive data types (If I remember correctly).
Hope it helps

Pulling data from one Tab Activity to another

Everything I've read about Intents talks about using them to push data, or to start one Activity from another Activity. I want to pull data from an Activity that's already running.
The Tab Layout tutorial at http://developer.android.com/resources/tutorials/views/hello-tabwidget.html illustrates what I want to do. (My app is doing some engineering calculations instead, but the tutorial code provides a good analogy to my app.) The tutorial creates an app with three tabs, and each tab hosts a separate activity.
To expand on the example in the tutorial, suppose I select an artist in the Artists tab/activity. I want to be able to select the Albums tab/activity and have it display all the albums featuring that artist.
It seems to me that I need to use an Intent to do this. All of the tutorials I've found assume that I would create a "See albums" Button in the Artists tab/activity, and that pressing the Button would execute an Intent that starts the Albums activity and passes artistName.
I DO NOT want to create that Button. Real estate on the Artists layout is precious, and I have a perfectly good Albums tab, AND the HelloTabWidget activity already contains an intent to create the Albums tab.
Besides, a user will want to skip back and forth between Album and Artist in order to change artist selections, and the tabs are a perfectly good way to do this. There's no need to complicate the UI with another button.
So how can I have the Albums activity PULL artistName from the Artists activity when the Albums tab is selected (or the Albums layout is displayed), rather than have the Artists activity START Albums and PUSH the artistName?
Equivalents I can think of from other programming worlds:
Global variables. Discouraged in Android devt, right? And if they do exist, what are they called?
A getter, like artistName = Artists.getArtistName(); . I get the feeling that it's not that easy.
Writing to, and reading from, a file - that is, mass storage or non-volatile memory. I don't need the artistName value to be permanent. It will be reset to null every time the user launches the application.
So how is it done in the Android world? Do I use an Intent - and if so, how?

Global variables were the right answer.
I thought Java discouraged their use, but a couple of links that appeared in the "Related" links on the right margin of this window mentioned them directly. One was "Android: How to declare global variables?" and the other was "how to pass value betweeen two tab in android". Both pointed to the Application Class as the place to define global variables and methods. Armed with this new knowledge, I found an article called "Android Application Class" on the Xoriant blog that expanded on the StackOverflow answers.
It's best to review those three links first. I need to add some tips to what those authors have said.
Your Application class has to be in its own separate file. (That might be a "duh" to some people, but not to everybody.) Here's a good framework for an example called Something.java:
public class Something extends Application {
// Put application wide (global) variables here
// Constants are final, so they don't have to be private
// But other variables should be declared private;
// use getters/setters to access them
public final boolean FEET = false;
public final boolean METERS = true;
private boolean units = FEET;
#Override
public void onCreate() {
super.onCreate();
// Put any application wide (global) initialization here
}
// Put application wide (global) methods here
public boolean getUnits() {
return units;
}
public void setUnits(boolean whichOne) {
units = whichOne;
}
}
I'm using Eclipse with the ADT plug-in, in Windows XP. Eclipse doesn't always behave properly if you edit XML code directly, so it's best to open AndroidManifest.xml, then select the Application tab and enter your application name in the Name field. You don't need to put a dot or period in front of the name. Just type in the name of your class, like "Globals" or "MyApplication" or whatever. (Note that this is the default application in your Manifest. You don't have to create a separate <application></application> tag.
This step may not be necessary on an actual Android device, but it was necessary for the emulator: you need to use the getApplicationContext() command in every onCreate() and every method that will be accessing the global variables and methods. I tried to put it outside of onCreate() with the rest of my activity wide variables, and it didn't work. Putting it inside every method seems wasteful, but both the emulator and the Android device work fine with it that way. Here's a sample showing how I used it:
public void fooBar() {
// Access to global variables and methods
final Something s = (Something)getApplicationContext();
// ...
// This next line demonstrates both a global method and a global variable
if (s.getUnits() == s.FEET) {
// do something with feet
} else {
// do something with meters instead
}
// ...
}
Those were the only hiccups I encountered. The three references that I have listed, taken together, are otherwise pretty complete.

get WebView instances stored in a ViewAnimator

I have some WebView instances that i stored in a ViewAnimator programmatically. Firstly i constructed each WebViesw. Then i add them into the ViewAnimator
WebView webview = new WebView(context);
viewAnimator.addView(webview, index, layoutparams);
While a webView being added into the ViewAnimator, an AsyncTask instance is executed to load webpage from a specific URL.
My question, how can i get a webView from that ViewAnimator for a particular index value. I want to do some specific actions to the webView, such as reload or stop. I have done this way..
WebView currentWebView = (WebView) viewAnimator.getChildAt(index);
currentWebView.reload();
But the currentWebView returned null. Is that the right way to get webView instance from ViewAnimator? Please help...

I don't know why getChildAt() return null, but as a workaround, you can maintain your own list of WebView. This is a stupid question, but are you sure your index is valid?