I'm working on eclipse (android) and I want to call outside a variable that is in the OnClick method. How can I do that? I thought to use a return but OnClick is a void method. Here is my code
backgroundE2.setOnClickListener(new View.OnClickListener(){
public void onClick(View view){
int randomIntE = random2.nextInt(Deck.length());
int drawableIDE = Deck.getResourceId(randomIntE, -1);
backgroundE2.setBackgroundResource(drawableIDE);
}
});
I'm trying to call the variable randomIntE. How can I do that if everything is closed? I have to call also other 4 variables that are in different setOnClickListener.
You can use a global variable declared outside the function.
public class MainActivity extends Activity {
int fnsetFlag= 0;
backgroundE2.setOnClickListener(new View.OnClickListener(){
public void onClick(View view){
fnsetFlag= 1;
}
});
}
you should save it somewhere, like in an instance variable or in an object that can be called from the piece of code you want to use.
I hope to have understand the question properly.
Andrea.
Related
So when we set an onClickListener to, say, a Button, it looks something like this.
private Button myButton = (Button) findViewById(R.id.my_button);
myButton.setOnClickListener(new View.OnClickListener(){
#Override
public void onClick(View view){
//do this
}
});
So we're creating a nameless anonymous class when we state new View.OnClickListener... and implementing the OnClickListener interface / and overriding it's onClick method. What I don't understand, is if we have no reference to this anon class, because it's nameless, how does the onClick() method get called? I've only ever implemented an anonymous class to override certain methods in said class, like this:
public class Foo{
public void bar(){
//do something
}
}
Foo foo = new Foo(){
#Override
public void bar(){
//do something else
}
}
This makes perfect sense to me because now, anytime I use the "foo" reference to call the bar() method, that reference will use the overridden version of bar. In the case of the Button, there's no reference to onClick(). I'm beyond confused about this.
If it helps your understanding, you could rewrite to this:
View.OnClickListener listener = new View.OnClickListener(){
#Override
public void onClick(View view){
//do this
}
};
myButton.setOnClickListener(listener);
The button holds the reference after listener goes out of scope, and can call the onClick callback on the held listener object.
What I don't understand, is if we have no reference to this anon class, because it's nameless, how does the onClick() method get called?
myButton is holding onto the instance of the anonymous inner class that you created. myButton, therefore, can call onClick() on it.
The onclick event is called in the button object and this object delegates to your anonymous class onclick with the reference you set.
i've already implemented this thing in my application using activity,
refer image link below
"http://imgur.com/LuErJjY"
in the first part you can see the context=PerformanceActivity#4015
but in the 2nd part it is null
the code i've used is
IN ACTIVITY:
viewHolder.nextReview.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
int d=v.getId();
((PerformanceActivity)context).performReview(v.getId());
}
});
IN FRAGMENT:
NOTE: PerformanceFragment pf;
viewHolder.nextReview.setId(resData.get(position).getTestID());
viewHolder.nextReview.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
int d=v.getId();
((PerformanceFragment)pf).performReview_frag(v.getId());
}
});
Both the methods are methods present in the adapter of a listview. In Activity It just works fine, but not in fragment.
Links to both adapters:
https://pastee.org/28chw - Fragment's Adapter https://pastee.org/nw8rr
- Fragment
https://pastee.org/wxepy -Activity's Adapter
At last this worked for me -
PerformanceFragmentAdapter adapter = new PerformanceFragmentAdapter(context,rsuData,device,this);
and adding this to the adapter as
private PerformanceFragment pf;
public PerformanceFragmentAdapter(Context conte, ArrayList<ResultData> rData,
int device, PerformanceFragment pp) {
super();
context = conte;
resData = rData;
size = device;
pf=pp;
}
guess #ursgtm is right. still confusing between Context c=getActivity(); and this keyword
In PerformanceFragmentAdapter class :
PerformanceFragment pf;
You are just creating a object with no instance and you are using that object as context,and you are not assigning anything to pf .
Instead of remove pf, and pass the context which you got from constructor:
viewHolder.nextReview.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
int d=v.getId();
//Replace ((PerformanceFragment)pf) with context
context.performReview_frag(v.getId()); //you obtained context from contractor.
}
});
Hope this helps you !
In second part use getActivity() method if your fragment PerformanceFragment is associated with your activity PerformanceActivity
viewHolder.nextReview.setId(resData.get(position).getTestID());
viewHolder.nextReview.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
int d=v.getId();
/* (getActivity()). no need to use content if
performReview_frag() is present in PerformanceFragment fragment*/
// this will call performReview_frag() method
performReview_frag(v.getId());
}
});
Else,
You can use getBaseContext() method to get correct context
If I want to design a button that all java can use it without need to write it in every java,
what should I do?
For Example:
I design a Button.OnClickListener function to search bluetooth devices.
but another java also need to use this Button.OnClickListener function,
I don't want to write same way on two java.
ledWrite.xml:
<Button android:id="#+id/btnScan" />
<ToggleButton android:id="#+id/tBtnWrite" />
bluetoothUtils.java
// Intent request codes
private static final int REQUEST_CONNECT_DEVICE = 1;
private Button button_scan;
button_scan = (Button)findViewById(R.id.button_scan);
button_scan.setOnClickListener(new OnClickListener(){
public void onClick(View v) {
scanbt();
}
});
private void scanbt(){
Intent serverIntent = new Intent(this, DeviceListActivity.class);
startActivityForResult(serverIntent, REQUEST_CONNECT_DEVICE);
}
then I design LedWrite.java:
private ToggleButton digitalOutBtn; //LED On/OFF
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.ledwrite);
digitalOutBtn = (ToggleButton)findViewById(R.id.tBtnWrite);
digitalOutBtn.setOnClickListener(new OnClickListener()
public void onClick(View v){
if(digitalOutBtn.isChecked()){ //sendMessage("D1"); }
else{sendMessage("D0";}
}
How can I use button_scan in LedWrite.java?
If you want to call a method defined is some other Activity on press of a button, then you can make that method as static.
Let's assume that you have a method named searchBluetooth() in MainActvity and you want to call it from SecondActivity.
Define searchBluetooth() in MainActvity like,
public static void searchBluetooth()
Call this method from SecondActivity like,
MainActivity.searchBluetooth()
If you don't want to use static because of memory consumption then try with inheritance.
Create a class CommonActivity which extends Activity class
class CommonActivity extends Activity
{
// here define your searchBluetooth method
public void searchBluetooth()
{
// your code here
}
}
If you want to make use of it in Second Activity then
class SecondActivity extends CommonActivity
{
// here you can access `searchBluetooth()` method
}
enclosure a BluetoothListener class?
public BluetoothListener implements OnClickListener {
#Override
public void onClick(View v) {
do something you want...
}
}
then invoke the class in two different class, eg,
button.setOnClickListener(new BluetoothListener());
I recently started learning android and this answer may have some error, if so, please let me know, Thanks.
I have trouble understanding this code. I get that findViewById will get the button widget and then it'll cast it. Then, it's going to use the button to call the setOnClickListener method. However, I don't know what is that argument being passed into the setOnClickListener and I have never seen code like that before. How is it that it creates a new object but is able to create a method of its own within another method's argument? Would be great if someone could explain that. Also, what type of object is the setOnClickListener method taking in?
btn = (Button)findViewById(R.id.firstButton);
btn.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v)
{
tv.setText(months[rand.nextInt(12)]);
tv.setTextColor(Color.rgb(rand.nextInt(255)+1, rand.nextInt(255)+1, rand.nextInt(255)+1));
}
});
It works like this. View.OnClickListenere is defined -
public interface OnClickListener {
void onClick(View v);
}
As far as we know you cannot instantiate an object OnClickListener, as it doesn't have a method implemented. So there are two ways you can go by - you can implement this interface which will override onClick method like this:
public class MyListener implements View.OnClickListener {
#Override
public void onClick (View v) {
// your code here;
}
}
But it's tedious to do it each time as you want to set a click listener. So in order to avoid this you can provide the implementation for the method on spot, just like in an example you gave.
setOnClickListener takes View.OnClickListener as its parameter.
This is the best way to implement Onclicklistener for many buttons in a row
implement View.onclicklistener.
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
This is a button in the MainActivity
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
bt_submit = (Button) findViewById(R.id.submit);
bt_submit.setOnClickListener(this);
}
This is an override method
#Override
public void onClick(View view) {
switch (view.getId()){
case R.id.submit:
//action
break;
case R.id.secondbutton:
//action
break;
}
}
That what manual says about setOnClickListener method is:
public void setOnClickListener (View.OnClickListener l)
Added in API level 1 Register a callback to be invoked when this view
is clicked. If this view is not clickable, it becomes clickable.
Parameters
l View.OnClickListener: The callback that will run
And normally you have to use it like this
public class ExampleActivity extends Activity implements OnClickListener {
protected void onCreate(Bundle savedValues) {
...
Button button = (Button)findViewById(R.id.corky);
button.setOnClickListener(this);
}
// Implement the OnClickListener callback
public void onClick(View v) {
// do something when the button is clicked
}
...
}
Take a look at this lesson as well Building a Simple Calculator using Android Studio.
its an implementation of anonymouse class object creation to give ease of writing less code and to save time
It works by same principle of anonymous inner class where we can instantiate an interface without actually defining a class :
Ref: https://www.geeksforgeeks.org/anonymous-inner-class-java/
So, I am again, asking a very basic question. I apologize for my ineptness but I guess I read the given tutorials on these topics poorly. My question is as follows:
I would like to use a "listener" pattern to handle button presses on my GUI. I believe an onClickListener is what I need to use to handle these button presses. However, I'm not sure if I should be creating and handling events that occur after the GUI is created within an onCreate method. The following code is within my onCreate method for one of my Activities:
View.OnClickListener upDownListener = new View.OnClickListener()
{
#Override
public void onClick(View v)
{
if(v == (upOneButton))
{
Log.d("OptionSelect", "Up One Button Pressed.");
ops.getOptionList().get(0).incrementProbability(4);
} . . .
This method being called updates some GUI text with a different number. It is being called, but the GUI isn't responding. I imagine this has to do with my attempt to use it within the onCreate method.
In short, what is a good and simple way to deal with user events within a GUI and where should this occur?
Thank you so much.
EDIT: Log.d() does in fact get called. Also, ops is an object of type OptionSelect which happens to be the type of the class in which the onCreate() call is made. Will that become an issue? Also, here is the method for incrementProbability():
public void incrementProbability(int numberOfOptions)
{
probability += (numberOfOptions - 1);
if(probability > 100)
{
Log.i("OptionSelect", "Exceeded Maximum by " + (probability - 100));
probability = 100;
}
}
Also, here is relevant code I should've included that is updating my GUI at the end of the onClick() method:
private void refreshDisplay(TextView a, TextView b, TextView c, TextView d)
{
a.setText(getOptionList().get(0).getProbability() + "");
b.setText(getOptionList().get(1).getProbability() + "");
c.setText(getOptionList().get(2).getProbability() + "");
d.setText(getOptionList().get(3).getProbability() + "");
a.invalidate();
b.invalidate();
c.invalidate();
d.invalidate();
}
Thanks for the help so far!
I personally prefer to have my Activities implement listener interfaces and add an onClick method to the Activity itself such as...
public class MyActivity extends Activity
implements View.OnClickListener {
...
#Override
public void onClick(View v) {
...
}
}
I then just use...
myGuiObject.setOnClickListener(this);
...whenever I want to set that method as the listener for any GUI object.