I am following a course on Udacity on android development. When I try something like this with auto complete:
listView.setOnItemClickListener(new AdapterView.OnItemClickListener() {
#Override
public void onItemClick(AdapterView<?> adapterView, View view, int i, long l) {
}
});
you can see that the primitive variable got the names i, and j. In this video, I believe android studio automatically gave the int variable the name "position". Do I need to enable this in android studio's settings, or is did the developer in the video just manually changed the name?
Much likely he changed it on his own. That's because the method of the AdapterView.Class defines the OnItemClickListener interface as follows:
public static interface OnItemClickListener {
void onItemClick(
android.widget.AdapterView<?> adapterView,
android.view.View view,
int i, // <-- position
long l);
}
As you can see, the position is named i that's why the Auto-Completion names it this way.
Related
To illustrate what I mean with this, it is similar to WhatsApp, where various options are displayed in the toolbar when a chat is selected.
I have a similar layout, so a MainActivity with Fragments containing RecyclerViews. Now when an item in a RecyclerView is selected I would like to get a similar behaviour as in WhatsApp. The RecyclerViews have an Adapter that implements an OnClickListener.
However, from this Adapter I do not seem to have access to Views from the MainActivity. I tried the following (inside the OnClick method in the Adapter), but it did not work since the view could not be found.
View view = getActivity().findViewById(R.id.toolbar_main_activity);
if( view instanceof Toolbar) {
Toolbar toolbar = (Toolbar) view;
toolbar.setTitle("TestTitle");
}
Does anyone know how to get the intended behavior or have a reference to a tutorial?
UPDATE: for who is also stuck with this and this is still quite confusing, here is how I solved it in my own words
My Fragment contains the Interface by adding the following code to it;
OnItemsSelected mCallBack;
public interface OnItemsSelected {
void onToolbarOptions(String title);
}
#Override
public void onAttach(Context context) {
super.onAttach(context);
mCallback = (OnItemsSelected) getActivity();
}
Also I passed 'mCallback' to the adapter like this;
MyAdapter adapter = new MyAdapter(myList, mCallback);
The RecyclerView adapter implements OnClickListener. In the OnClick method I called; 'mCallBack.onToolbarOptions("someTitle");'. And finally I made my MainActivity implement the method; 'implements myFragment.onItemsSelected' and I added the following code to it also;
#Override
public void onToolbarOptions(String title) {
toolbar.setTitle(title);
}
With this, only the title is changed, but from this it is quite easy to make other changes to the toolbar, such as changing the menu items.
Inside your Fragment you make an Interface and a global variable like this:
OnItemsSelected mCallBack;
public interface OnItemsSelected {
public void onToolbarOptions();
}
Then when in your RecyclerView items are selected or clicked you call:
mCallBack.onToolbarOptions();
In your Activity implement the Interface like this plus the method onToolbarOptions():
public static class YourActivityName extends AppCompatActivity
implements YourFragmentName.OnItemsSelected {
public void onToolbarOptions(){
// CHANGE YOUR TOOLBAR HERE
}
//.....OTHER STUFFS IN YOUR ACTIVITY
}
Whether I try to change a textView or a button, why does Android Studio require that I pass only chars and not strings in the setText() method?
Strings are automatically converted to CharSequences when necessary (or are CharSequences; can't remember. The point is, they're compatible):
public class Main {
public static void testF(CharSequence seq) {
System.out.println(seq);
}
public static void main(String[] args) {
testF("Hello"); // Prints "Hello"
}
}
This would have been a good thing to try on your own or search for first.
In a cross platform Xamarin app built with the MvvmCross framework I'm using a ToggleButton Widget in an Android .axml layout. I've bound the Checked property to a View Model property using a converter using the following binding syntax:
Checked MarketBuySellViewModel.Direction, Converter=DirectionBool, ConverterParameter='Sell'
Everything works well. On the iOS side, it appears you can use UIButton as a ToggleButton by using the Selected property. This implies that the following binding should achieve what I want on iOS:
set.Bind (SellButton).For(b => b.Selected).To (vm => vm.MarketBuySellViewModel.Direction).WithConversion("DirectionBool", "Sell");
I don't get any binding errors in the application output but the binding itself doesn't seem to work. Clicking the button doesn't set the Direction property and setting the direction to a different value does not set the Selected property on the UIButton.
Do I need to create a Custom Binding or am I simply setting up the binding incorrectly?
I also tried using a UISegmentedControl to achieve the same effect. Is binding to this control supported at all in MvvmCross? I don't see any reference to it in the source code. Does this mean I need to create custom bindings for it too?
For the UIButton, I don't believe there's any included Selected binding built into MvvmCross. Because of this - and because Selected doesn't have a simple paired event SelectedChanged, then I believe Selected binding should work one-way (from ViewModel to View) but not two-way.
There is a binding for the On of a UISwitch control and that's the control I've seen used most in these situations.
If you wanted to add a custom 2-way binding for Selected then I guess you'd have to do this using the ValueChanged event (but would need to check that is correct).
To do so, you'd just build a target binding something like:
public class MvxUIButtonSelectedTargetBinding : MvxPropertyInfoTargetBinding<UIButton>
{
public MvxUIButtonSelectedTargetBinding(object target, PropertyInfo targetPropertyInfo)
: base(target, targetPropertyInfo)
{
var view = View;
view.ValueChanged += HandleValueChanged;
}
private void HandleValueChanged(object sender, System.EventArgs e)
{
var view = View;
if (view == null)
return;
FireValueChanged(view.Selected);
}
public override MvxBindingMode DefaultMode
{
get { return MvxBindingMode.TwoWay; }
}
protected override void Dispose(bool isDisposing)
{
base.Dispose(isDisposing);
if (isDisposing)
{
var view = View;
if (view != null)
{
view.ValueChanged -= HandleValueChanged;
}
}
}
}
and this could be registered in Setup in protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry) using something like:
registry.RegisterPropertyInfoBindingFactory(typeof(MvxUIButtonSelectedTargetBinding), typeof(UIButton),
"Selected");
Similarly, I don't believe anyone has added a two way UISegmentedControl binding yet - but would happily see one added.
Building a two way UISegmentedControl binding would be quite straight-forward - you'd just have to bind to the pair SelectedSegment and ValueChanged - with code similar to above.
Alternatively, you could switch to using a custom MySegmentedControl which had a nicer Value`ValueChanged` pair which would automatically work without a custom binding - e.g.:
public class MySegmentedControl : UISegmentedControl
{
// add more constructors if required
public int Value
{
get { return base.SelectedSegment; }
set { base.SelectedSegment = value; }
}
}
If any or all of these custom bindings are needed, then the Mvx project is happy to get these bindings added as issues or pull requests along with test/demo UIs in the https://github.com/slodge/MvvmCross-Tutorials/blob/master/ApiExamples/ApiExamples.Touch/Views/FirstView.cs project
Could be helpful to someone else, so i'm sharing my experience. I needed a two way binding for UISegmentedControl.SelectedSegment property to a ViewModel. The one way biding (ViewModel => View) works by default. I couldn't able to properly utilize the solution proposed by Stuart - to subclass the UISegmentedControl. I tried to ensure that the linker does not rip off the new custom control code, but this didn't help me a bit. So a perfectly viable solution is the one with MvxPropertyInfoTargetBinding. Here is the code working ok for me:
public class MvxUISegmentedControlSelectedSegmentTargetBinding : MvxPropertyInfoTargetBinding<UISegmentedControl>
{
public MvxUISegmentedControlSelectedSegmentTargetBinding(object target, PropertyInfo targetPropertyInfo)
: base(target, targetPropertyInfo)
{
this.View.ValueChanged += HandleValueChanged;
}
private void HandleValueChanged(object sender, System.EventArgs e)
{
var view = this.View;
if (view == null)
{
return;
}
FireValueChanged(view.SelectedSegment);
}
public override MvxBindingMode DefaultMode
{
get { return MvxBindingMode.TwoWay; }
}
protected override void Dispose(bool isDisposing)
{
base.Dispose(isDisposing);
if (isDisposing)
{
var view = this.View;
if (view != null)
{
view.ValueChanged -= HandleValueChanged;
}
}
}
}
public class Setup : MvxTouchSetup
{
...
protected override void FillTargetFactories(IMvxTargetBindingFactoryRegistry registry)
{
registry.RegisterPropertyInfoBindingFactory(typeof(MvxUISegmentedControlSelectedSegmentTargetBinding), typeof(UISegmentedControl), "SelectedSegment");
}
}
I am making an application using LWUIT.
There is a form
There is a list embedded on the form.
The list has 5 elements.
Initially, when I first load the app, if I choose the 1st element, 2nd gets chosen; when I choose the second the 3rd gets chose and and so on (Weird!)
I am not able to click any button on the screen either
next what I do is, shift to a different from using arrow keys (of the keyboard... I am running the app on a simulator btw)
Then I come back to the first form and now everything works as expected(no weird behaviour).
What could be the issue?
I am using Sun Java Micro Edition SDK 3.0 (default touch screen for testing)
My code is:
List dummy = new List();
dummy.addItem("wewerwer");
dummy.addItem("wewerdswer");
dummy.addItem("wewqweerwer");
dummy.addItem("dscxwewerwer");
dummy.addItem("jhgwewerwer");
mainListForm.setLayout(new BorderLayout());
mainListForm.addComponent(BorderLayout.CENTER,dummy);
mainListForm.show();
What could possible be going wrong here?
UPDATE 1
I think there is a bug here. I have attached the complete code below along with the screen shot
import javax.microedition.midlet.*;
import com.sun.lwuit.*;
import com.sun.lwuit.events.*;
import com.sun.lwuit.plaf.UIManager;
import com.sun.lwuit.util.Resources;
public class Demo extends MIDlet implements ActionListener {
private Form mForm;
List abc;
public void startApp() {
Display.init(this);
try {
Resources r = Resources.open("/Test.res");
UIManager.getInstance().setThemeProps(r.getTheme(
r.getThemeResourceNames()[0])
);
} catch (Exception e){
System.out.println(e.toString());
}
if (mForm == null) {
Button click = new Button("Press me!");
click.addActionListener(new ActionListener() {
public void actionPerformed(ActionEvent ae) {
System.out.println("I have been pressed");
}
});
abc = new List();
abc.addItem("Str1");
abc.addItem("Str2");
abc.addItem("Str3");
abc.addItem("Str4");
abc.addItem("Str5");
abc.addItem("Str6");
Form f = new Form("Hello, LWUIT!");
abc.addActionListener(this);
f.addComponent(abc);
Command exitCommand = new Command("Exit");
f.addCommand(exitCommand);
f.addCommandListener(this);
f.addComponent(click);
f.show();
}
}
public void pauseApp() {
}
public void destroyApp(boolean unconditional) {
}
public void actionPerformed(ActionEvent ae) {
System.out.println(abc.getSelectedIndex());
}
}
So now when I click on 'Str1' of the list Str2 gets selected and so on.
IDE: Netbeans
Emulator: Default Touch screen phone
On the action event set the list to active again after the event by invoking setHandlesInput(true)
OK....so this is how you resolve it.
After the form is displayed remove the list from the form and again add it to the form and then repaint the form.
Earlier Code
1) form.addComponenet(BorderLayout.center,list);
2) form.show();
Word Around for the problem
1)form.addComponenet(BorderLayout.center,list);
2)form.show();
3)form.setScrollable(false);
I know its kind of strange, but this way the list index selection works smooth for touch screen phones.
I am working my way through the NeHe OpenGL examples, using the LWJGL for the OpenGL binding inside an Eclipse RCP application.
My OpenGL graphics are displayed inside the RCP canvas, not in a separate window.
Lesson 07 shows how to use the keyboard. If I try to do a:
Keyboard.create();
I get an error that the (OpenGL) "Display" has not been created.
If I create an OpenGL "Display" with org.lwjgl.opengl.Display.create(), then I get a new Window.
So how do I access the Keyboard without creating a new Window?
You cannot use the Keyboard without a Display, because of how LWJGL works behind the scenes. The best way is to just use AWT events. You can write your own input class, that could go something like this.
public class Input implements KeyListener {
private boolean aDown; //is the A key down?
//Ect, for all needed keys
public void keyPressed(KeyEvent ke) {
switch (ke.getKeyCode()) {
case KeyEvent.VK_A: aDown = true; break;
//and so on for all other needed keys.
}
}
public void keyReleased(KeyEvent ke) {
switch (ke.getKeyCode()) {
case KeyEvent.VK_A: aDown = false; break;
//and so on for all other needed keys.
}
}
public void keyTyped(KeyEvent ke) {} //Do nothing
public void isADown() {return aDown;}
}