I am new to android and java world hardly 3 months working on it. Hence please help with me. I have gridview which display default images. My requirement is when user click on the item set product image for some time e.g. 2/3 seconds and again display default image. Please let me know how can I handle this. Sample code will be appreciated.
Currently I have following non working code which always show default image
gridview.setOnItemClickListener(new OnItemClickListener() {
public void onItemClick(AdapterView<?> parent, View imgView,
int position, long id) {
ImageAdapter adapter = (ImageAdapter) parent.getAdapter();
ImageView imageView = (ImageView) imgView;
imageView.setImageResource(R.drawable.productImage);
Thread.sleep(1000);
imageView.setImageResource(R.drawable.bg_default_card);
}
});
I found the workaround. I create object of Runnable and set image to default image in run method
I put following code in onItemClick event. I create one class level variable for imageview e.g. imgView1 assign the clicked image to imgView1 onItemClick event
//create runable object
Runnable r1 = new Runnable() {
public void run() {
//check imageView1 not null
if (imgView1 != null) {
//set image to default
imgView1.setImageResource(R.drawable.bg_default_card);
}
}
};
//call runnable after some interval
imgView1.postDelayed(r1, 500);
Thank you.
Related
I have found that on iOS, OnAppearing is called when the page literally appears on the screen, whereas on Android, it's called when it's created.
I'm using this event to lazily construct an expensive to construct view but obviously the Android behaviour defeats this.
Is there some way of knowing on Android when a screen literally appears on the screen?
You can use the event:
this.Appearing += YourPageAppearing;
Otherwise, you should use the methods of the Application class that contains the lifecycle methods:
protected override void OnStart()
{
Debug.WriteLine ("OnStart");
}
protected override void OnSleep()
{
Debug.WriteLine ("OnSleep");
}
protected override void OnResume()
{
Debug.WriteLine ("OnResume");
}
On Android, Xamarin.Forms.Page.OnAppearing is called immediately before the page's view is shown to user (not when the page is "created" (constructed)).
If you want an initial view to appear quickly, by omitting an expensive sub-view, use a binding to make that view's IsVisible initially be "false". This will keep it out of the visual tree, avoiding most of the cost of building it. Place the (invisible) view in a grid cell, whose dimensions are constant (either in DPs or "*" - anything other than "Auto".) So that layout will be "ready" for that view, when you make it visible.
APPROACH 1:
Now you just need a binding in view model that will change IsVisible to "true".
The simplest hack is to, in OnAppearing, fire an action that will change that variable after 250 ms.
APPROACH 2:
The clean alternative is to create a custom page renderer, and override "draw".
Have draw, after calling base.draw, check an action property on your page.
If not null, invoke that action, then clear it (so only happens once).
I do this by inheriting from a custom page base class:
XAML for each of my pages (change "ContentPage" to "exodus:ExBasePage"):
<exodus:ExBasePage
xmlns:exodus="clr-namespace:Exodus;assembly=Exodus"
x:Class="YourNamespace.YourPage">
...
</exodus:ExBasePage>
xaml.cs:
using Exodus;
// After creating page, change "ContentPage" to "ExBasePage".
public partial class YourPage : ExBasePage
{
...
my custom ContentPage. NOTE: Includes code not needed for this, related to iOS Safe Area and Android hardward back button:
using Xamarin.Forms;
using Xamarin.Forms.PlatformConfiguration.iOSSpecific;
namespace Exodus
{
public abstract partial class ExBasePage : ContentPage
{
public ExBasePage()
{
// Each sub-class calls InitializeComponent(); not needed here.
ExBasePage.SetupForLightStatusBar( this );
}
// Avoids overlapping iOS status bar at top, and sets a dark background color.
public static void SetupForLightStatusBar( ContentPage page )
{
page.On<Xamarin.Forms.PlatformConfiguration.iOS>().SetUseSafeArea( true );
// iOS NOTE: Each ContentPage must set its BackgroundColor to black or other dark color (when using LightContent for status bar).
//page.BackgroundColor = Color.Black;
page.BackgroundColor = Color.FromRgb( 0.3, 0.3, 0.3 );
}
// Per-platform ExBasePageRenderer uses these.
public System.Action NextDrawAction;
/// <summary>
/// Override to do something else (or to do nothing, i.e. suppress back button).
/// </summary>
public virtual void OnHardwareBackButton()
{
// Normal content page; do normal back button behavior.
global::Exodus.Services.NavigatePopAsync();
}
}
}
renderer in Android project:
using System;
using Android.Content;
using Android.Views;
using Android.Graphics;
using Xamarin.Forms;
using Xamarin.Forms.Platform.Android;
using Exodus;
using Exodus.Android;
[assembly: ExportRenderer( typeof( ExBasePage ), typeof( ExBasePageRenderer ) )]
namespace Exodus.Android
{
public class ExBasePageRenderer : PageRenderer
{
public ExBasePageRenderer( Context context ) : base( context )
{
}
protected override void OnElementChanged( ElementChangedEventArgs<Page> e )
{
base.OnElementChanged( e );
var page = Element as ExBasePage;
if (page != null)
page.firstDraw = true;
}
public override void Draw( Canvas canvas )
{
try
{
base.Draw( canvas );
var page = Element as ExBasePage;
if (page?.NextDrawAction != null)
{
page.NextDrawAction();
page.NextDrawAction = null;
}
}
catch (Exception ex)
{
// TBD: Got Disposed exception on Android Bitmap, after rotating phone (in simulator).
// TODO: Log exception.
Console.WriteLine( "ExBasePageRenderer.Draw exception: " + ex.ToString() );
}
}
}
}
To do some action after the first time the page is drawn:
public partial class YourPage : ExBasePage
{
protected override void OnAppearing()
{
// TODO: OnPlatform code - I don't have it handy.
// On iOS, we call immediately "DeferredOnAppearing();"
// On Android, we set this field, and it is done in custom renderer.
NextDrawAction = DeferredOnAppearing;
}
void DeferredOnAppearing()
{
// Whatever you want to happen after page is drawn first time:
// ((MyViewModel)BindingContext).ExpensiveViewVisible = true;
// Where MyViewModel contains:
// public bool ExpensiveViewVisible { get; set; }
// And your XAML contains:
// <ExpensiveView IsVisible={Binding ExpensiveViewVisible}" ... />
}
}
NOTE: I do this differently on iOS, because Xamarin Forms on iOS (incorrectly - not to spec) calls OnAppearing AFTER the page is drawn.
So I have OnPlatform logic. On iOS, OnAppearing immediately calls DeferredOnAppearing. On Android, the line shown is done.
Hopefully iOS will eventually be fixed to call OnAppearing BEFORE,
for consistency between the two platforms.
If so, I would then add a similar renderer for iOS.
(The current iOS implementation means there is no way to update a view before it appears a SECOND time, due to popping the nav stack.
instead, it appears with outdated content, THEN you get a chance
to correct it. This is not good.)
I'm trying to get this animation/transition working in my Xamarin Android application with Mvx.
I have a recyclerview with cards. When tapping on a card, I now call:
private void TimeLineAdapterOnItemClick(object sender, int position)
{
TimeLineAdapter ta = (TimeLineAdapter) sender;
var item = ta.Items[position];
int photoNum = position + 1;
Toast.MakeText(Activity, "This is photo number " + photoNum, ToastLength.Short).Show();
ViewModel.ShowDetails(item.Id);
}
I'm trying to find out how to translate this java navigation with transition to Xamarin with Mvvmcross:
ActivityOptionsCompat options =
ActivityOptionsCompat.MakeSceneTransitionAnimation(this, imageView, getString(R.string.activity_image_trans));
startActivity(intent, options.toBundle());
I know that within Mvx you can make use of custom presenters, but how do I get hold of, for example, the ImageView of the tapped Card within the RecyclerView which I would like to 'transform' to the new ImageView on the new Activity?
Thanks!
.
Is there a Xamarin Mvvmcross Android Shared Element Navigation
example?
I do not believe so.
I know that within Mvx you can make use of custom presenters, but how
do I get hold of, for example, the ImageView of the tapped Card within
the RecyclerView which I would like to 'transform' to the new
ImageView on the new Activity?
The easiest way that I can think of to achieve the sharing of control elements you want to transition is via the use of view tags and a presentation bundle when using ShowViewModel.
I would suggest making some changes to your Adapter Click handler to include the view of the ViewHolder being selected (See GitHub repo for example with EventArgs). That way you can interact with the ImageView and set a tag that can be used later to identity it.
private void TimeLineAdapterOnItemClick(object sender, View e)
{
var imageView = e.FindViewById<ImageView>(Resource.Id.imageView);
imageView.Tag = "anim_image";
ViewModel.ShowDetails(imageView.Tag.ToString());
}
Then in your ViewModel, send that tag via a presentationBundle.
public void ShowDetails(string animationTag)
{
var presentationBundle = new MvxBundle(new Dictionary<string, string>
{
["Animate_Tag"] = animationTag
});
ShowViewModel<DetailsViewModel>(presentationBundle: presentationBundle);
}
Then create a custom presenter to pickup the presentationBundle and handle the creating of new activity with the transition. The custom presenter which makes use of the tag to find the element that you want to transition and include the ActivityOptionsCompat in the starting of the new activity. This example is using a MvxFragmentsPresenter but if you are not making use of fragments and using MvxAndroidViewPresenter the solution would be almost identical (Override Show instead and no constructor required).
public class SharedElementFragmentsPresenter : MvxFragmentsPresenter
{
public SharedElementFragmentsPresenter(IEnumerable<Assembly> AndroidViewAssemblies)
: base(AndroidViewAssemblies)
{
}
protected override void ShowActivity(MvxViewModelRequest request, MvxViewModelRequest fragmentRequest = null)
{
if (InterceptPresenter(request))
return;
Show(request, fragmentRequest);
}
private bool InterceptPresenter(MvxViewModelRequest request)
{
if ((request.PresentationValues?.ContainsKey("Animate_Tag") ?? false)
&& request.PresentationValues.TryGetValue("Animate_Tag", out var controlTag))
{
var intent = CreateIntentForRequest(request);
var control = Activity.FindViewById(Android.Resource.Id.Content).FindViewWithTag(controlTag);
control.Tag = null;
var transitionName = control.GetTransitionNameSupport();
if (string.IsNullOrEmpty(transitionName))
{
Mvx.Warning($"A {nameof(transitionName)} is required in order to animate a control.");
return false;
}
var activityOptions = ActivityOptionsCompat.MakeSceneTransitionAnimation(Activity, control, transitionName);
Activity.StartActivity(intent, activityOptions.ToBundle());
return true;
}
return false;
}
}
GetTransitionNameSupport is an extension method that just does a platform API check when getting the TransitionName.
public static string GetTransitionNameSupport(this ImageView imageView)
{
if (Build.VERSION.SdkInt >= BuildVersionCodes.Lollipop)
return imageView.TransitionName;
return string.Empty;
}
The final step would be to register the custom presenter in you Setup.cs
protected override IMvxAndroidViewPresenter CreateViewPresenter()
{
var mvxPresenter = new SharedElementFragmentsPresenter(AndroidViewAssemblies);
Mvx.RegisterSingleton<IMvxAndroidViewPresenter>(mvxPresenter);
return mvxPresenter;
}
You can check the repo on GitHub which demonstrates this example. The solution is designed so that the presenter does not have to care about the type of the control that is being transitioned. A control only requires a tag used to identify it. The example in the repo also allows for specifying multiple control elements that you want to transition (I did not want to include more complexity in the example above).
Guys Im using the following custom code to load 20 images from resources and present in a viewpager
public class CustomPagerAdapter extends PagerAdapter {
int[] mResources = {
R.drawable.slide1,
R.drawable.slide2,
R.drawable.slide3,
R.drawable.slide4,
R.drawable.slide5,
R.drawable.slide6,
R.drawable.slide7,
R.drawable.slide8,
R.drawable.slide9,
R.drawable.slide10,
R.drawable.slide11,
R.drawable.slide12,
R.drawable.slide13,
R.drawable.slide14,
R.drawable.slide15,
R.drawable.slide16,
R.drawable.slide17,
R.drawable.slide18,
R.drawable.slide19,
R.drawable.slide20,
};
Context mContext;
LayoutInflater mLayoutInflater;
public CustomPagerAdapter(Context context) {
mContext = context;
mLayoutInflater = (LayoutInflater) mContext.getSystemService(Context.LAYOUT_INFLATER_SERVICE);
}
#Override
public int getCount() {
return mResources.length;
}
#Override
public boolean isViewFromObject(View view, Object object) {
return view == ((LinearLayout) object);
}
#Override
public Object instantiateItem(ViewGroup container, int position) {
View itemView = mLayoutInflater.inflate(R.layout.pager_item, container, false);
ImageView imageView = (ImageView) itemView.findViewById(R.id.imageView);
imageView.setImageResource(mResources[position]);
container.addView(itemView);
return itemView;
}
#Override
public void destroyItem(ViewGroup container, int position, Object object) {
container.removeView((LinearLayout) object);
}
}
This works fine but I want to put the jpgs in a directory on the device so that they can be changed without recompiling the app
I think I need to get the images into the mResource array. I can get the path but not sure what format the code should be instead of using the draw-able lines
i have read articles on here but none make sense to me I am really new to this and the code looks nothing like the code I am using
can anyone point me in the right direction?
Any help is greatly appreciated
Mark
Yes, you can certainly do so. I will try to explain you the process step-by-step,
Step 1
Have a File object pointing to the path, like,
File directory = new File("path-to-directory");
Ensure that the path is to the directory with the images,
Step 2
List all the files inside the directory using listFiles() method, like
File[] allImages = directory.listFiles();
Now you have an array of all the files just like int[] mResources. The only difference being, now you have actual file references, while previously you had resource ids.
Step 3
You can just display the images in the ViewPager just like you did previously. But this is a bit tricky and can take you a considerable amount of time and code to get an image properly displayed from File.
You also need to take care of caching, so that when you load a previously loaded image again, it gets it from the cache.
To do all this, I recommend you to use this library (recommended by Google), Glide.
Setting an image is one line of code,
Glide.with(context).from(file).into(imageView);
That's it. Now you have your images displayed in a ViewPager from a directory in the device.
I need to recreate new page instance on every page load (also when user pressed Back button).
So I overrided OnBackKeyPress method:
protected override void OnBackKeyPress(CancelEventArgs e)
{
base.OnBackKeyPress(e);
if (NavigationService.CanGoBack) {
e.Cancel = true;
var j = NavigationService.RemoveBackEntry();
NavigationService.Navigate(j.Source);
NavigationService.RemoveBackEntry();
}
}
The problem is that I can't handle case when user press back button to close CustomMessageBox dialog. How can I check it? Or is there any way to force recreation of page instance when going back through history state?
Why do you need to recreate the page instance? If you are simply trying to re-read the data to be displayed, why not put the data loading logic into OnNavigatedTo()?
Assuming that is what you are actually trying to achieve, try something like this...
public partial class MainPage : PhoneApplicationPage
{
// Constructor
public MainPage()
{
InitializeComponent();
// don't do your data loading here. This will only be called on page creation.
}
protected override void OnNavigatedTo(NavigationEventArgs e)
{
LoadData();
base.OnNavigatedTo(e);
}
MyViewModel model;
async void LoadData()
{
model = new MyViewModel();
await model.LoadDataAsync();
}
}
If you also have specific logic that you need to run on first construction of the page vs. on a back key navigation, check the NavigationMode property of the NavigationEventArgs object that gets passed to OnNavigatedTo.
if(e.NavigationMode == NavigationMode.New)
{
//do what you need to do specifically for a new page instance
}
if (e.NavigationMode == NavigationMode.Back)
{
// do anything specific for back navigation here.
}
Ha, in the near thread, i have opposite question :)
What about MessageBox - it depends, which one are you using. It can be custom message box, for example. Anyway, try to check MessageBox.IsOpened (or alternative for your MessageBox) in your OnBackKeyPress().
Another solution is to use OnNavigatedTo() of the page you want to be new each time.
Third solution: in case you works with Mvvm Light, add some unique id in ViewModel getter, like
public MyViewModel MyViewModel
{
get
{
return ServiceLocator.Current.GetInstance<MyViewModel>((++Uid).ToString());
}
}
This would force to recreate new ViewModel each time, so you'd have different instance of VM, so you would have another data on the View.
I am trying to create a tool bar with background color different from the screen background,
i am using the following code
getMainManager().add(mToolbarManager = new HorizontalFieldManager());
mToolbarManager.add(mBtn = new BitmapButtonField(mBmpNor, mBmpFoc,
mBmpAct));
Background bg = BackgroundFactory.createSolidBackground(Color.BLACK);
mToolbarManager.setBackground(bg);
mToolbarManager.add(mBtn = new BitmapButtonField(mBmpNor, mBmpFoc,
mBmpAct));
but it doesn't effect the background of toolbarmanager, while setting the background of mainmanager works fine
I got it , i used call HorizontalFieldManager constructor with USE_ALL_WIDTH parameter
hey i know 1 more way that i used:
class Mymanager extends Manager
{
final Bitmap back = Bitmap.getBitmapResource("back.png");
Mymanager ()
{
super(Manager.NO_VERTICAL_SCROLL);
}
public void paint(Graphics g)
{
g.drawBitmap(0,0,back.getWidth(),back.getHeight,back,0,0);
}
}
no add components to this manager