[Q] Need help with webbrowser control - Windows Phone 7 Software Development

Hey, I'm building an app and somewhere in it I'm using the IE webbrowser control to display some info. But for some reason I can't the physical 'back' button to correspond to the webbrowser, it always just exits the app. Does anybody know how I can get around this, or actually make the 'back' button correspond to the webbrowser control? Any help is greatly appreciated.

You need to handle this your self by overriding the OnBackKeyPress method. There is also no "Back" function in the webbrowser control so you will have to store a list of all the pages the user has visited within your control and use the Navigate method to go to the last one when the user clicks back.
Sent from my 7 Pro T7576 using Board Express

Wow thank you. Is there any simple way of going about this?

I'm going to bump this.

Basically, you need to declare:
private List<string> _history = new List<string>();
Hook onto the LoadCompleted event:
http://msdn.microsoft.com/en-us/lib...ntrols.webbrowser.loadcompleted(v=VS.95).aspx
Then, within your LoadCompleted handler, do:
_history.Add(webBrowser1.Source.AbsoluteUri);
Now you need to override the OnBackKeyPress:
protected override void OnBackKeyPress(object o, EventArgs e) {
// If there is history available
if(_history.Count > 0) {
// Navigate to the item
webBrowser1.Navigate(new Uri(_history.Last());
// Remove the item from the history stack
_history.Remove(_history.Last());
// Stop the screen from executing the default back button behaviour
e.Cancel = true;
}
base.OnBackKeyPress();
}
That's all a basic outline of what you need to do. As a developer, you can fill the rest in and improve upon this yourself

You'd do better with a Stack instead of a List for the history. Note that serializing the Stack to IsolatedStorageSettings for tombstoning is problematic, but converting the Stack to a List for tombstoning works.

manicotti said:
You'd do better with a Stack instead of a List for the history. Note that serializing the Stack to IsolatedStorageSettings for tombstoning is problematic, but converting the Stack to a List for tombstoning works.
Click to expand...
Click to collapse
As you say, you would probably end up converting the stack to a list for enumeration at some stage anyway, so it'd be easier to stick with the list throughout. Plus the performance improvement would be unnoticable at best.
Sent from my 7 Pro T7576 using Board Express

Related

CheckBox state presrving/restoring

Hi there,
Does anyone out there how to preserve/restore the transient state of a CheckBox and/or Radio button?
So far, I'm using the following code, working for textbox
Code:
Public Sub PreserveState_TextBox(ByVal TB As TextBox)
Dim buffer As String = String.Empty
If True = PhoneApplicationService.Current.State.ContainsKey(TB.Name) Then
buffer = TryCast(PhoneApplicationService.Current.State(TB.Name), String)
If Not String.IsNullOrEmpty(buffer) Then
TB.Text = buffer
End If
End If
End Sub
Public Sub RestoreState_TextBox(ByVal TB As TextBox)
If True = PhoneApplicationService.Current.State.ContainsKey(TB.Name) Then
PhoneApplicationService.Current.State.Remove(TB.Name)
End If
PhoneApplicationService.Current.State.Add(TB.Name, TB.Text)
End Sub
it possible to modify the above code to work for Checkbox and/or Radiobutton?
If not, any ideas?
So far, I've been trying the sample "Tombstoning" sample code from Microsoft without any luck...
Thanks in advance!
Hi,
I'm not a VB developer, but storing the state of a checkbox is not much different from storing any other primitive type. What you could do is have a bool variable "isCbChecked" and store that bool state in your PhoneApplicationService.State.
Code:
PhoneApplicationService.Current.State.Add("isCbChecked", myCheckbox.IsChecked)
Then, when you're restoring your app, simply do
Code:
myCheckbox.IsChecked = (bool)PhoneApplicationService.Current.State.ContainsKey("isCbChecked");
keyboardP said:
Hi,
I'm not a VB developer, but storing the state of a checkbox is not much different from storing any other primitive type. What you could do is have a bool variable "isCbChecked" and store that bool state in your PhoneApplicationService.State.
Code:
PhoneApplicationService.Current.State.Add("isCbChecked", myCheckbox.IsChecked)
Then, when you're restoring your app, simply do
Code:
myCheckbox.IsChecked = (bool)PhoneApplicationService.Current.State.ContainsKey("isCbChecked");
Click to expand...
Click to collapse
Thanks a lot for your fast reply.
Can I ask for additional help on how to make your statements into generic procedures, at least to take them to something similar to what I posted?
Don't care if it's in C#
Thanks in advance!
GFR_2009 said:
Thanks a lot for your fast reply.
Can I ask for additional help on how to make your statements into generic procedures, at least to take them to something similar to what I posted?
Don't care if it's in C#
Thanks in advance!
Click to expand...
Click to collapse
Off the top of my head, something like this should work (C# code).
Code:
public static T RestoreState<T>(string key)
{
if (PhoneApplicationService.Current.State.ContainsKey(key))
{
return (T)PhoneApplicationService.Current.State[key];
}
return null;
}
'T' is the type that will be used. In C# 'T' is a special character denoting the generic type, not something I just used
So in the code above, the return type is 'T' and when using RestoreState, it will be 'RestoreState<Textbox>("TB.Name");'. The value of 'TB.Name' will be searched within the dictionary and, if it's found, it will cast that object as 'T' (Textbox) and return it, otherwise it will return null.
Hi,
So far, I did the following and while no error is raised, nothing happens...
Code:
Public Function Backup(ByVal token As String, ByVal value As Object) As Boolean
If Nothing Is value Then
Return False
End If
Dim store = PhoneApplicationService.Current.State
If store.ContainsKey(token) Then
store(token) = value
Else
store.Add(token, value)
End If
Return True
End Function
Public Function Restore(Of T)(ByVal token As String) As T
Dim store = PhoneApplicationService.Current.State
If Not store.ContainsKey(token) Then
Return Nothing
End If
Return CType(store(token), T)
End Function
I call them as follows
Code:
Backup(Me.CheckBox_1.Name, Me.CheckBox_1)
Restore(Of CheckBox)(Me.CheckBox_1.Name)
Don't where is the error, maybe you could take a look and help me out.
Any help is much appreciated!
Where are you calling the Backup and Restore functions? Since your doing page specific things, you could do it in the OnNavigatedFrom and OnNavigatedTo methods, respectively.
keyboardP said:
Where are you calling the Backup and Restore functions? Since your doing page specific things, you could do it in the OnNavigatedFrom and OnNavigatedTo methods, respectively.
Click to expand...
Click to collapse
Hi,
I'm calling them in the OnNavigatedTo and OnNavigatedFrom methods, as you pointed out
Unfortunately, nothing happens at all!
Thanks!
Hi,
As far as I can tell, there's nothing wrong with your saving/loading code. When you call
"Restore(Of CheckBox)(Me.CheckBox_1.Name)", is that returning a bool? You need to assign that bool to the checkbox:
Code:
myCheckbox.IsChecked = Restore(Of CheckBox)(Me.CheckBox_1.Name);
Also, all variables are reset when the page loads, so make sure you have set "myCheckbox.IsChecked" anywhere else on the page that could be called when the page loads.
Please, check the converted code of the above functions, to C#
Code:
public bool Backup(string token, object value)
{
if (null == value)
{
return false;
}
var store = PhoneApplicationService.Current.State;
if (store.ContainsKey(token))
{
store(token) = value;
}
else
{
store.Add(token, value);
}
return true;
}
public T Restore<T>(string token)
{
var store = PhoneApplicationService.Current.State;
if (! (store.ContainsKey(token)))
{
return default(T);
}
return (T)(store(token));
}
Do you think they are OK?
How should I call them ?
Clearly, the restore does not returns a boolean...
Honestly, I'm lost now!
Hope this helps to find the culprit.
It seems okay to me. You'll have to do some debugging. Set a breakpoint inside the Backup and Restore methods. Step through each line and make sure it's going to the line you expect it to and that the value being set is the correct one.
I haven't seen the tombstoning sample from MSDN, but can you get that to work? If so, is the generic method causing the problem? Or can you not get it to work at all?
Hi,
Sorry for the delay in getting back, but I was trying different codes and at least I found the cause.
Code:
Me.NavigationService.Navigate(New Uri("/PivotPage1.xaml?Name=" & "John", UriKind.Relative))
[B]Me.NavigationService.GoBack[/B]()
Me.NavigationService.Navigate(New Uri("/PivotPage1.xaml", UriKind.Relative))
Everything works fine, and the Checkbox state is saved/restored (in the Pivot Page) if I GO BACK using the GoBack hardware button or Me.NavigationService.GoBack
But, the state's dictionary entry is lost or ignored if I go back with the Navigate service (lines 1 and 3)...
Problem is that I need to get back with the query string...
The query string contains a value taken in the SelectedItem event of PAGE2's ListBox, and automatically once retrieved must go back.
I didn't know until know, that NavigationService.Navigate creates a new page instance or something like that in the backstack...
Any sugestions are welcomed!
Hi,
There are various methods you can use depending on the app's architecture. For example, you could have a 'shared' class that contains a shared field that holds the SelectedItem value. When the user selects the item, set the shared field's value and then when you go back, you can get the value from the shared field.
keyboardP said:
Hi,
There are various methods you can use depending on the app's architecture. For example, you could have a 'shared' class that contains a shared field that holds the SelectedItem value. When the user selects the item, set the shared field's value and then when you go back, you can get the value from the shared field.
Click to expand...
Click to collapse
So, no other way to cope with the navigation service?
It's a strange behaviour for sure...
Will try your ideas.
Thanks a lot for your reply!
GFR_2009 said:
So, no other way to cope with the navigation service?
It's a strange behaviour for sure...
Will try your ideas.
Thanks a lot for your reply!
Click to expand...
Click to collapse
There are other ways. For example, instead of using the PhoneApplicationService to store the tombstoning information, you could put it in a querystring for page 2. Then, in page 2, you could add the information from the previous page to a querystring AND the information of the selected item to the querystring. Navigate to page 1, with the querystring that contains information on what was there before and what the user selected. Tombstoning is there for when the user presses the hardware search button, home button, a phone call arrives etc.. It's not there for the navigation of the app. That's where querystrings, shared variables, binary serialization etc... come into play.
The concept of the navigation service is similar to a website. For example, when you submit something and then go back, it might still be there in the page state. However, if you submit something and then reload the previous page by typing it in the address bar, it becomes a completely new page as no state is stored.
keyboardP said:
There are other ways. For example, instead of using the PhoneApplicationService to store the tombstoning information, you could put it in a querystring for page 2. Then, in page 2, you could add the information from the previous page to a querystring AND the information of the selected item to the querystring. Navigate to page 1, with the querystring that contains information on what was there before and what the user selected. Tombstoning is there for when the user presses the hardware search button, home button, a phone call arrives etc.. It's not there for the navigation of the app. That's where querystrings, shared variables, binary serialization etc... come into play.
The concept of the navigation service is similar to a website. For example, when you submit something and then go back, it might still be there in the page state. However, if you submit something and then reload the previous page by typing it in the address bar, it becomes a completely new page as no state is stored.
Click to expand...
Click to collapse
Hi,
Will try your suggested approach, and thanks a lot for the last explanation on how the darn thing works.
Thanks again!
GFR_2009 said:
Hi,
Will try your suggested approach, and thanks a lot for the last explanation on how the darn thing works.
Thanks again!
Click to expand...
Click to collapse
You're welcome . It's one of those things that take a bit of time to understand, but starts to make sense. You might be interested in a free WP7 development ebook by Charles Petzold.
keyboardP said:
You're welcome . It's one of those things that take a bit of time to understand, but starts to make sense. You might be interested in a free WP7 development ebook by Charles Petzold.
Click to expand...
Click to collapse
I already have the book, but will need a deeper reading
So far, I've been testing your idea of using global classes and works ok.
Thanks a lot for being so cooperative, it's much appreciated!
GFR_2009 said:
I already have the book, but will need a deeper reading
So far, I've been testing your idea of using global classes and works ok.
Thanks a lot for being so cooperative, it's much appreciated!
Click to expand...
Click to collapse
No worries! If programming was super easy everyone would be doing it
keyboardP said:
No worries! If programming was super easy everyone would be doing it
Click to expand...
Click to collapse
Never said better!

[Q] Dynamic UI Creation XAML, C#

this is my first post. I am pretty desperate at the moment.
I would like to dynamically create the UI for the WP7 based on a CSV file in Isolated Storage. right now I would settle for just being able to write the UI in XAML from the code behind in C#.
steps that I would like to execute:
1. user clicks a muscle group button which passes a value to another page-done
2. users data is pulled from CSV file and placed in array for easy storage-done
3. for each data element create a XAML TextBlock with the data which is displayed in the UI <-- need some serious help
best I can do is show the XAML code with the <> tags as a string in the UI.
is what I am asking possible?
Thanks for helping.
Knudmt said:
this is my first post. I am pretty desperate at the moment.
I would like to dynamically create the UI for the WP7 based on a CSV file in Isolated Storage. right now I would settle for just being able to write the UI in XAML from the code behind in C#.
steps that I would like to execute:
1. user clicks a muscle group button which passes a value to another page-done
2. users data is pulled from CSV file and placed in array for easy storage-done
3. for each data element create a XAML TextBlock with the data which is displayed in the UI <-- need some serious help
best I can do is show the XAML code with the <> tags as a string in the UI.
is what I am asking possible?
Thanks for helping.
Click to expand...
Click to collapse
Sounds like what you really want to do is dynamically create controls in the code-behind. I would forget about generating "XAML".
Code:
private void AddTextboxesFromCSV(string[] CSVData) {
foreach(string str in CSVData) {
TextBlock tb = new TextBlock();
tb.Name = "txtUserSelectedValue" + CSVData.IndexOf(str);
tb.Text = str;
<YourObject>.Controls.Add(tb);
}
}
Where <YourObject> is the object you want to place the controls into, some sort of layout Panel.
Thanks for the response
I think that is the direction I will be going. Just out of curiosity do you know if what I wanted to do is even possible?
UN app for WP7 does something like this. Go to http://unitednations.codeplex.com/releases/view/57722 and grab the source. Open the source in Visual Studio and browse to the "Framework" folder and open up "BasePage.cs". At the bottom there's a method called AddNavigatingText() that does what I think you are looking to do.
Here's the method:
Code:
protected Grid AddNavigatingText()
{
var NavigatingText = (Grid) XamlReader.Load(
@" <Grid xmlns=""http://schemas.microsoft.com/winfx/2006/xaml/presentation""
xmlns:x=""http://schemas.microsoft.com/winfx/2006/xaml"" Height=""30"" VerticalAlignment=""Top"" Background=""#CCFFFFFF"">
<TextBlock HorizontalAlignment=""Left"" TextWrapping=""Wrap"" Text=""Navigating..."" Width=""129"" FontSize=""{StaticResource PhoneFontSizeNormal}"" Margin=""24,0,0,0"" FontFamily=""{StaticResource PhoneFontFamilySemiBold}""/>
<ProgressBar Style=""{StaticResource PerformanceProgressBar}"" RenderTransformOrigin=""0.5,0.5"" Margin=""135,0,0,0"" UseLayoutRounding=""False"" Background=""White"" IsIndeterminate=""True"" LargeChange=""0"" />
</Grid>");
this.Content.As<Grid>().Children.Add(NavigatingText);
return NavigatingText;
}
Thanks for the reply. Looks pretty simple. I downloaded the source and signed up for codeplex. However I can not connect to the tfs.codeplex.com
It's not possible to use dynamically created XAML; code is the way to go and much easier IMHO.
When you open the project just hit cancel at the login screen and it will load.
sulphuricaciduk said:
It's not possible to use dynamically created XAML; code is the way to go and much easier IMHO.
Click to expand...
Click to collapse
Agreed, doing it via code with a very basic XAML based page is likely to be faster, and will actually work. It's also a lot easier to fix things than trying to work out what went wrong in XAML you can't see...
I would agree with the statement that creating the controls dynamically would be faster. And def a great deal easier to read It just bugs me when I know this can be accomplished, yet I cant get it to work
Blade0rz said:
Sounds like what you really want to do is dynamically create controls in the code-behind. I would forget about generating "XAML".
Code:
private void AddTextboxesFromCSV(string[] CSVData) {
foreach(string str in CSVData) {
TextBlock tb = new TextBlock();
tb.Name = "txtUserSelectedValue" + CSVData.IndexOf(str);
tb.Text = str;
<YourObject>.Controls.Add(tb);
}
}
Where <YourObject> is the object you want to place the controls into, some sort of layout Panel.
Click to expand...
Click to collapse
Well that worked very well, thanks! I am having a little formatting issue .. my textblocks show up right on top of each other. any ideas?
Thanks again
Knudmt said:
Well that worked very well, thanks! I am having a little formatting issue .. my textblocks show up right on top of each other. any ideas?
Thanks again
Click to expand...
Click to collapse
I solved this silly issue. just added a listbox control to the xaml front end and added my elements with an ugly cast
listbox1.items.add((TextBlock)myBlock);
Knudmt said:
I solved this silly issue. just added a listbox control to the xaml front end and added my elements with an ugly cast
listbox1.items.add((TextBlock)myBlock);
Click to expand...
Click to collapse
If you had a StackPanel as the parent control, you could have each new textblock stacked...

[Q] NavigationService and form controls

I have a main form with a load of controls on it. I have a listbox, and a piece of code that is looking at individual items eg:
Code:
dim listitem as listboxitem = me.listbox.item(0)
when i use the navigationservice.navigate function to navigate to a different page, and then navigate back to the main page i can no longer edit that list box. The code still runs and doesnt error, but the list item is not updating. Its almost like there are two instances of the form open.
Any ideas?
thanks
when im navigating back to the main form i am using another navigationservice.navigate. Im guesing this is creating a new form everytime you use the .navigate as when i use navigationservice.goback from the second form it works fine.
To that end, is there a way you can close a form once you have navigated away from it using .navigate? and can you navigate to an already open form (without creating a new instance) and without using .goforward?
thanks (im using vb silverlight by the way)
adamrob69 said:
... i can no longer edit that list box. The code still runs and doesnt error, but the list item is not updating. Its almost like there are two instances of the form open.
Click to expand...
Click to collapse
Hmm... Could you explain what do you mean? How do you "edit" list box?
Post your code and explain what are you trying to do.
P.S. Have you tried to trace your code with breakpoints on the page constructors? Just try - you will be very surprised
Code:
''MainForm
sub EditListBox()
dim listitem as listboxitem = me.listbox.item(0)
listitem.content = "New List Text"
end sub
sub Navigate()
NavigationService.Navigate(new uri("/Page2.xml",relative))
end sub
Code:
''Form 2
sub NavigateBack()
NavigationService.Navigate(new uri("/MainForm.xml",relative))
end sub
The EditListBox() routine is called every x mins from a system timer. When navigated to form2 then back again the code still runs, i can put a break in and can see it running through the code but the listbox isn't updating. I believe this is because when you use the NavigationService.Navigate function it creates a new instance of the page. On form2 if I use NavigationSevice.GoBack instead of .navigate the main form updates the listbox correctly.
So if that is the case; is there a way you can close a form once you have navigated away from it using NavigationService.navigate? and can you navigate to an already open form (without creating a new instance) and without using .goforward?
I've already gave you a hint (to debug constructors). Yes, if you are using NavigationService.Navigate(new Uri("/MainPage.xaml", UriKind.Relative)); or NavigationService.Source = new Uri("/MainPage.xaml", UriKind.Relative); it creates a new page.
This implementation have a sense if you start thinking in web-based terms (what is Silverlight built for!)
BTW, I don't understand your requirements. Why do you need this? What's wrong with GoBack() or GoForward()? Also, have you tried other WP7 layouts (Panorama etc.)?
Try to follow the MS "Metro UI" recommendations and many questions will disappear shortly...
GoFoward won't work:
http://msdn.microsoft.com/en-us/lib...ation.navigationservice.goforward(VS.92).aspx
It seems like your problem isn't navigation, (because you should be using GoBack) but that the previous page that you GoBack to isn't how you wanted it.
If this is the case, you should add some sort of way to tell an event occurred. For example, if you did (note this is really rough)
Page2.xaml.cs
{
...
public static bool VisitedPage = false;
...
}
and when you visit the page, simply set it to true.
Then, when you GoBack, in OnNavigatedTo
protected override void OnNavigatedTo(NavigationEventArgs e)
{
if (Page2.VisitedPage)
{
//process why you needed to go tot he page
//clear the page for a fresh run
}
}
Have you tried unselecting that listbox item when you goback?
I had this same issue not too long ago where since it was the same instance of the page the listbox item was still selected when I returned and since the event on the listbox is "selectedchanged" it doesnt change when you select the same 1.

[Q] How to implement Transparent Labels and other controls [vb.net]

I've been banging my head against this one all morning and now i have a head ache so i decided to stick it out to you lot.
I want to make all my user controls (labels, checkbox's etc) transparent - well the text at least. I found this thread on MSDN but i'll be honest and say i'm not entirely sure what i'm supposed to do with it.
Thanks for your thoughts.
Works a treat. Lifted the code from the site and dropped it straight into the form class.
Code:
using System;
using System.Collections.Generic;
using System.ComponentModel;
using System.Data;
using System.Drawing;
using System.Text;
using System.Windows.Forms;
using Microsoft.WindowsCE.Forms;
namespace TestDevApp
{
public partial class Form1 : Form
{
public Form1()
{
InitializeComponent();
}
forum.xda-developers.com/search.php?searchid=90851847
private void pictureBox1_Paint(object sender, PaintEventArgs e)
{
DrawLabel(label1,e.Graphics);
DrawLabel(label2, e.Graphics);
DrawLabel(label3, e.Graphics);
DrawLabel(label4, e.Graphics);
}
private void DrawLabel(Label label, Graphics gfx)
{
if (label.TextAlign == ContentAlignment.TopLeft)
{
gfx.DrawString(label.Text, label.Font, new SolidBrush(label.ForeColor), label.Bounds);
}
else if (label.TextAlign == ContentAlignment.TopCenter)
{
SizeF size = gfx.MeasureString(label.Text, label.Font);
float left = ((float)this.Width + label.Left) / 2 - size.Width / 2;
RectangleF rect = new RectangleF(left, (float)label.Top, size.Width, label.Height);
gfx.DrawString(label.Text, label.Font, new SolidBrush(label.ForeColor), rect);
}
else //is aligned at TopRight
{
SizeF size = gfx.MeasureString(label.Text, label.Font);
float left = (float)label.Width - size.Width + label.Left;
RectangleF rect = new RectangleF(left, (float)label.Top, size.Width, label.Height);
gfx.DrawString(label.Text, label.Font, new SolidBrush(label.ForeColor), rect);
}
}
}
}
Devtrans is the view in VS
Transparent is the actual running code.
Cool thanks.
I did try using DrawString but the drawn text doesn't scroll with the form when you... well.... scroll the form.
I'm gonna have the afternoon off but i will check it out properly later. Would this also work for check boxes? If so what are the changes that would need to be made?
Checkboxes might be a different matter. The above method does not work, it only deals with the text caption. There is is an article on The Code Project at
http://www.codeproject.com/KB/dotnet/TransparentControl.aspx
It appears like they have almost created a control from scratch. You may have to take control/override that much of the object, to get it to work, that you have almost created a new control.
stephj said:
Checkboxes might be a different matter. The above method does not work, it only deals with the text caption. There is is an article on The Code Project at
http://www.codeproject.com/KB/dotnet/TransparentControl.aspx
It appears like they have almost created a control from scratch. You may have to take control/override that much of the object, to get it to work, that you have almost created a new control.
Click to expand...
Click to collapse
I did see that page but i couldn't figure out how the hell to use it
Ok, so now you have found one of the BIGGEST challenges to WM development.
I spent 4+ months trying to get the same thing you are looking for (well, what I assume you are looking for), that is: A transparent label that you can use your finger to scroll.
If that is what you are looking for, I can tell you right now that you need to either look into custom controls that already do this or decide how much time you are willing to invest into something as simple as that.
Here is the basic components that you will need to code to get DrawString to properly scroll with your finger:
You will need to code up some kind of container or panel that holds the current virtual x,y coordinates.
You will need to code up some kind of custom control that can be added to the previously made container
Create logic in the container to take the current virtual x,y coords and determine which custom controls are visible and should be drawn on the screen, pass them their offset coords, and draw the control
Override the OnMouse*ACTION* events on the container to manipulate the virtual x,y coords and then refresh the screen
You also will need to know about double buffering so you don't get any flickering.
It's a very very hard thing to do on WinMo, something that other platforms take for granted. This is one of the reasons that some custom WinMo programs have UIs that are either really terrible, or take tons of resources.
If you want to give it a go (and I would highly recommend doing it, I can't tell you how much I learned about software development by creating my own custom controls) I can help point you in the right directions. Feel free to take a look at the code I've written for my Facebook app (specifically the XFControls and SenseUI projects). I'm not on XDA as often as I'd like, but send me a PM with your questions and I'll respond when I log in.
Good Luck!

[HELP] Can we use native libs in a module? Mine dies as soon as a lib is added.

Hi,
First, a disclaimer.
I am a Java and xposed noob. My background is in embedded C development so I can get by with some simple Java code and thanks to the great tutorials online I have been able to put together an xposed module but I'm struggling with a problem that is beyond my abilities now and am reaching out to the community for help.
Next, the background.
I have an Android head unit in my car. There is an app that provides me with CarPlay functionality but none of the controls on the steering wheel work with the app. When I analysed the code I found that they handle all of their button inputs using proprietary methods that do not inject an event into any input streams. I wrote an xposed module to hook the button press methods and then inject a proper input into one of the event streams.
Initially I tried to use the command line 'input' command to do this but since it is a Java app and takes about 1s to load it was too slow. My only other option was to create a virtual device on an input stream that I could then use to inject keypresses through the hooked method. To create a virtual device I needed to write C code that my xposed module would be able to access through the JNI. Long story short, after some pain I was able to get the native library integrated into the project and compiling using the NDK.
Finally, the problem.
When I was using the module without the native library it worked but just with a large delay because of the time it takes to load the 'input' java app. I was able to see logs from the module in the logcat as I hooked the method and as I went through the various actions within the hook.
As soon as I introduce the native library though the entire xposed module just stops running completely. I do not get any logs from the module even though I have installed, activated and rebooted. It shows up in the xposed installer but it just does nothing. The funny thing is that this happens even if I make no reference whatsoever to any native functions within the library. All I need to do to kill the module is to build it with the System.loadlibrary line in the Main.java uncommented. As soon as I comment that piece of code out the module starts to hook the function and output logs again. Below is the code from the Main.Java that I am referring to. I am happy to make any manifest, C and gradle files available too. Looking for any ideas as to why the module dies completely as soon as I include this...
Code:
package projects.labs.spike.zlink_xposed_swc;
import de.robv.android.xposed.XposedBridge;
import static de.robv.android.xposed.XposedHelpers.findAndHookMethod;
import de.robv.android.xposed.IXposedHookLoadPackage;
import de.robv.android.xposed.IXposedHookZygoteInit;
import de.robv.android.xposed.XSharedPreferences;
import de.robv.android.xposed.XC_MethodHook;
import de.robv.android.xposed.callbacks.XC_LoadPackage;
import de.robv.android.xposed.XposedHelpers;
import android.app.AndroidAppHelper;
import android.content.Intent;
import android.os.Bundle;
import android.content.Context;
/* shellExec and rootExec methods */
import java.io.DataOutputStream;
import java.io.IOException;
import java.io.InputStream;
import java.io.ByteArrayOutputStream;
import android.view.KeyEvent;
import android.media.AudioManager;
public class Main implements IXposedHookLoadPackage {
public static final String TAG = "ZLINK_XPOSED ";
public static void log(String message) {
XposedBridge.log("[" + TAG + "] " + message);
}
//public native int CreateVirtualDevice();
//public native int SendPrev();
@Override
public void handleLoadPackage(final XC_LoadPackage.LoadPackageParam lpparam) throws Throwable {
log("handleLoadPackage: Loaded app: " + lpparam.packageName);
if (lpparam.packageName.equals("com.syu.ms")) {
findAndHookMethod("module.main.HandlerMain", lpparam.classLoader, "mcuKeyRollLeft", new XC_MethodHook() {
@Override
protected void afterHookedMethod(XC_MethodHook.MethodHookParam param) throws Throwable {
// previous
log("PREVKEYHIT");
//rootExec("input keyevent 88");
log("EVENTSENT");
//Below was trying to use media keys which zlink never responded to...
/* Context context = (Context) AndroidAppHelper.currentApplication();
AudioManager mAudioManager = (AudioManager) context.getSystemService(Context.AUDIO_SERVICE);
KeyEvent event = new KeyEvent(KeyEvent.ACTION_DOWN, KeyEvent.KEYCODE_MEDIA_PREVIOUS);
mAudioManager.dispatchMediaKeyEvent(event);
KeyEvent event2 = new KeyEvent(KeyEvent.ACTION_UP, KeyEvent.KEYCODE_MEDIA_PREVIOUS);
mAudioManager.dispatchMediaKeyEvent(event2);*/
//Below is the failed broadcast intent method...
/*Context mcontext = (Context) AndroidAppHelper.currentApplication();
Intent i = new Intent("com.android.music.musicservicecommand");
i.putExtra("command", "pause");
mcontext.sendBroadcast(i);*/
}
});
}
}
public static String rootExec(String... strings) {
String res = "";
DataOutputStream outputStream = null;
InputStream response = null;
try {
Process su = Runtime.getRuntime().exec("su");
outputStream = new DataOutputStream(su.getOutputStream());
response = su.getInputStream();
for (String s : strings) {
s = s.trim();
outputStream.writeBytes(s + "\n");
outputStream.flush();
}
outputStream.writeBytes("exit\n");
outputStream.flush();
try {
su.waitFor();
} catch (InterruptedException e) {
e.printStackTrace();
}
res = readFully(response);
} catch (IOException e) {
e.printStackTrace();
} finally {
Closer.closeSilently(outputStream, response);
}
return res;
}
public static String readFully(InputStream is) throws IOException {
ByteArrayOutputStream baos = new ByteArrayOutputStream();
byte[] buffer = new byte[1024];
int length = 0;
while ((length = is.read(buffer)) != -1) {
baos.write(buffer, 0, length);
}
return baos.toString("UTF-8");
}
static {
System.loadLibrary("native-lib");
}
}
Have you tried capturing an ADB log _during the bootup_?
Xposed bugs in general are unfortunaley hard to identify and harder to fix, since the underlying code isn't well understood and/or maintained by many people.
Namnodorel said:
Have you tried capturing an ADB log _during the bootup_?
Xposed bugs in general are unfortunaley hard to identify and harder to fix, since the underlying code isn't well understood and/or maintained by many people.
Click to expand...
Click to collapse
Thanks for the response. I think that I have it figured out. The System.loadlibrary method looks for the native library within a path relative to the process that it is running within. The code within the apk ultimately does not run within that apk process, it runs within the xposed process. You therefore need to give xposed an absolute path to the library using the system.load method instead. Going to do some fiddling tonight and see if it works.
looxonline said:
Thanks for the response. I think that I have it figured out. The System.loadlibrary method looks for the native library within a path relative to the process that it is running within. The code within the apk ultimately does not run within that apk process, it runs within the xposed process. You therefore need to give xposed an absolute path to the library using the system.load method instead. Going to do some fiddling tonight and see if it works.
Click to expand...
Click to collapse
What about an alternative without using library we discussed earlier? Are you planning to test this as well?
If so, please let me know how it went.
C3C076 said:
What about an alternative without using library we discussed earlier? Are you planning to test this as well?
If so, please let me know how it went.
Click to expand...
Click to collapse
I didn't try it yet for two reasons.
1.) From the research I have done it seems as if my app would need the system INJECT_EVENTS permission in order to send keypress events outside of its own process. I cannot get this permission unless I sign my apk with the system cert that the ROM is compiled with. Maybe the method that you are using in the suggestion does not need this cert? Have you personally used this to inject key events across processes? I did see that you are getting the context of the system input service so maybe that solves this issue if the request appears to come from that PID...???
2.) The unit that I am working with has only two input devices and none of them have the keycodes I require. Does your method use a completely virtual device that is created on the fly? If so then it could work well without the need for me to create an HID input device.
I mostly was just on a role with the method that I was trying and I didn't want to turn back since I was so far down the road. I'm sure you understand how addictive certain challenges become and its quite fun to try to get them working even if they may not be the most optimal way.
In any case I managed to get the native library working last night and can successfully convince Android that I have a real HID keyboard plugged in and then send key events through that keyboard. Still not done though as there are a few hiccups that need solving. May still try your original suggestion. Thanks
looxonline said:
I didn't try it yet for two reasons.
1.) From the research I have done it seems as if my app would need the system INJECT_EVENTS permission in order to send keypress events outside of its own process. I cannot get this permission unless I sign my apk with the system cert that the ROM is compiled with. Maybe the method that you are using in the suggestion does not need this cert? Have you personally used this to inject key events across processes? I did see that you are getting the context of the system input service so maybe that solves this issue if the request appears to come from that PID...???
2.) The unit that I am working with has only two input devices and none of them have the keycodes I require. Does your method use a completely virtual device that is created on the fly? If so then it could work well without the need for me to create an HID input device.
I mostly was just on a role with the method that I was trying and I didn't want to turn back since I was so far down the road. I'm sure you understand how addictive certain challenges become and its quite fun to try to get them working even if they may not be the most optimal way.
In any case I managed to get the native library working last night and can successfully convince Android that I have a real HID keyboard plugged in and then send key events through that keyboard. Still not done though as there are a few hiccups that need solving. May still try your original suggestion. Thanks
Click to expand...
Click to collapse
I see.
1) Depends on in what process (package) your hooks are running within because permissions of this process apply of course, not the permissions you define in your module's manifest.
I am using key injecting method within "android" process (package) which means it works without me needing to worry about INJECT_EVENTS permission as "android" process already has it.
By the way, missing permissions are not of a big issue when developing with xposed as you can really do some magic with it.
E.g. I was adding some functionality to SystemUI that required some additional permissions that SystemUI typically lacks. So my module takes care of it.
https://github.com/GravityBox/Gravi...eco/pie/gravitybox/PermissionGranter.java#L75
C3C076 said:
I see.
1) Depends on in what process (package) your hooks are running within because permissions of this process apply of course, not the permissions you define in your module's manifest.
I am using key injecting method within "android" process (package) which means it works without me needing to worry about INJECT_EVENTS permission as "android" process already has it.
By the way, missing permissions are not of a big issue when developing with xposed as you can really do some magic with it.
E.g. I was adding some functionality to SystemUI that required some additional permissions that SystemUI typically lacks. So my module takes care of it.
https://github.com/GravityBox/Gravi...eco/pie/gravitybox/PermissionGranter.java#L75
Click to expand...
Click to collapse
Wow! I had no idea that you can use an xposed helper function to grant permissions to whatever process you are hooked within like that. That is VERY cool. Thanks so much for sharing

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