I have a GridView in a layout. It is populated with Foo views by the activity using a extended BaseAdapter.
When I select an item in this grid it gets orange tinted (thus selected). That's nice. But I want to access this selection from outside the GridView and it's parent activity: from within another View higher in the layout hierarchy. I therefor call upon gridView.getSelectedItem(). However it always returns null.
How could I get this to work?
"Selection" doesn't mean the same thing in AndroidOS as it does in other UIs. In particular, there isn't any "selected item" when you're in touch mode. You probably need to use a click listener instead of relying on there being a "selected item". See this article for details.
You can use the following to get the view:
View childView = gridView.getChildAt(position - gridView.getFirstVisiblePosition());
Related
Hello i have just started learning android application development and i am watching a lot of tutorials but none of them really describe step by step so my question is :
i have created a simple app which contains on TextView one EditText and one Button
i have added android:onClick="onButtonClick" to my Button so it will trigger the onButtonClick method , now , i would like it to print out the userinput from EditText so what i did is :
public void onButtonClick(View v){
Toast.makeText(v.getContext(), email.getText().toString(), Toast.LENGTH_SHORT).show();
}
but why the method has to contain the View v ? where is it passed from ? and what does it contain ? it contains the button which i clicked ? and what does the v.getContext() do? why my app does the same when replacing the v.getContext() with this ?
That are many questions at once, but I try to answer them one by one.
but why the method has to contain the View v ? where is it passed from ? and what does it contain ?
Consider the documentation of View.OnClickListener:
View: The view that was clicked.
So you are correct in your assumption that it is the View that has been clicked.
and what does the v.getContext() do?
The first parameter of the Toast#makeText method is a Context. Basically the Context is a container of global information in an Android application. The Toast needs it to retrieve information to show itself.
why my app does the same when replacing the v.getContext() with this ?
I assume your method resides in an Activity. An Activity is a subclass of Context and can be used as a parameter.
If you click a button then View is passed. ViewGroup is a group of View example LinearLayout, Relative Layout, FrameLayout,etc. View is a part of ViewGroup. According to Official Documentation, A View occupies a rectangular area on the screen and is responsible for drawing and event handling. View is the base class for widgets, which are used to create interactive UI components (buttons, text fields, etc.). The ViewGroup subclass is the base class for layouts, which are invisible containers that hold other Views (or other ViewGroups) and define their layout properties.
I hope you understand well about what is View and ViewGroup!!
I want to develop an Android app, where start page of the app GUI, will contain 4 vertical layouts in the main layout. Now, in each layout, I want to add buttons/slider dynamically from the app (instead of adding buttons/slider dynamically in the source code). That means, initially all these 4 layouts will be blank and when user will select any button or slider in another layout, to add it in any of this 4 layouts, the button or slider will be added in that layout. User will be able to add max 10 views in any vertical layout and the views can be either button, slider or custom view.
My attempt:
First I tried to create 4 vertical layout under the main layout for startup page and I got succeed.
I also find after searching that its possible to add views dynamically in layouts in android.
dynamically adding a view to activity layout
But most examples, add views dynamically in android by running loops, instantiating the desired view class and then add it in the main layout. Although, in this way, views are added dynamically in the layout, it is done by modifying the source code.
Is it possible to write the source code in a way, so that it can be done directly from the app? So that when user will click on Add a slider in "layout 1", a slider will be added in layout 1 and then again, when the user will click on "Add a button" in layout 1, a button will be added at the end of the slider. User will be able to customize button or slider properties. Also, if the user change the value of the slider, the app will remember its value.
Now, next time, when the app will be opened, those views will be there in the layouts, they will not be deleted and the values will remain unchanged (for example, a ticked check box will remain ticked), so I think I also need some kind of storage or properties manager.
My question is, is it possible to do this in android (because I never seen such apps in android) and if possible, any idea, how can I implement it?
I am totally new to android, so my knowledge is limited but I completed the basic tutorials on android app development and I have plugin development experience in eclipse.
Thanks a lot in. I will highly appreciate your help.
Of course it is possible:
Every layout (like LinearLayout, RelativeLayout etc.) extends the ViewGroup-class, which offers the addView-method.
To add a new view (like a Slider) to one of your layouts, just instantiate it programmatically (via new) in your activity and assign the appropriate LayoutParams to it
To store the state of user added content, it is the easiest to use SharedPreferences - a simple key-value-store which holds data over the application's lifecycle
Yes. This is possible. To create the Views dynamically, you simply have to either extend the class of the View or just say new Button(Context, AttributeSet); (Not only for Button's every View has a constructor that takes an attribute set and a context).
Using Layout.addView() you can add any View to the Layout.
Using SharedPreferences you can indicate what View belongs in what Layout.
If you decide to extend the View's class, make sure not to do too much in it. I tried that once and it just gave me an OOM (OutOfMemory Error) because I had a ton a Views trying to do stuff at the same time.
I have 2 buttons
I want only one of them to be selected at most at a time.
how can i find a view's sibling while in onClick ?
I have tried:
siblingView = v.getParent().findViewById(R.id.rightBtn);
but parentView has no findViewById method.
is it possible to get an ancestor view (even not direct) ? which is view for sure?
getParentView return type is an interface ViewParent
you can test if it is actually a View (or do not test, if you are sure), and downcast it to View.
If I understand this correctly, you need some kind of tabs, not two buttons.
Check this out for more details about how to implement that kind of behavior, using tabs not buttons.
I have an android activity with a webView.
How can I hide/close this webView?
is this the proper way?
webView.setVisibility(0);
You need to use the setVisibility(int visibility) method that all the various UI components inherit from the View class.
The documentation says that it can take either of the three values from View class:
1. VISIBLE: This view is visible
2. INVISIBLE: This view is invisible, but it still takes up space for layout purposes.
3. GONE: This view is invisible, and it doesn't take any space for layout purposes.
Now, use the method as and when needed with the appropriate constants from the View class.
Since you want to hide, I believe you will need to use webView.setVisibility(View.GONE)
you can hide any View by calling yourView.setVisibility(View.INVISIBLE) or yourView.setVisibility(View.GONE);
Difference: INVISIBLE means your View in not visible anymore, but it still takes its screen space. GONE means the View is completely hidden and doesn't take any space
I have a ListView with a header and a footer. I added two items with a class of my own extending the ArrayAdapter class. In this extended class, I have overridden the getView function because I want Views which are not TextViews to appear in my ListView.
On this ListView, I have set an onClickListener.
The problem is that this onClickListener is started when I click either on the header or on the footer, but never when I click on my items.
Of course, the View returned by getView is set to be clickable.
What am I missing?
Do you want to do something different when each list element is clicked? If so, you should programmatically set an onClickListener for each of those 2 elements added. Can you post your code?
It sounds like you are making this much more complicated than necessary. You can create your own layout for each row of a ListView using an XML file. This allows you to use any combinations of Views that you wish. To control what happens when the user clicks on a row in the ListView, your activity class should extend ListActivity and override onItemClickListener(). Alternatively, you can call setOnItemClickListener() on your ListView. For more details, I suggest that you read the Android ListView Developer Guide.
The solution I found : the click listener attached to the 'ListView' is only used for the clicks on the header and the footer. For my custom rows, in my ArrayAdapter's 'getView' function, I attached one listener to the 'TextView' and another to the 'ImageButton'.