Develop Reference

Call void method from another method in the same class

At first my main problem was at how to call a method from the same class, even tough I think I found a way to do this, it's not working as I expected, and I would like to know what would be the best approach to my case.
This is the code I'm working on:
public class EscolhaAtendimento extends AppCompatActivity {
private ViewPager mSlideViewPager;
private LinearLayout mDotLayout;
String TAG = "TasksSample";
private TextView[] mDots;
private SliderAdapter sliderAdapter;
Dialog myDialog;
#Override
public void onCreate (Bundle SavedInstanceState){
super.onCreate(SavedInstanceState);
setContentView(R.layout.escolha_atendimento);
mSlideViewPager = findViewById(R.id.slideViewPager);
mDotLayout = findViewById(R.id.dotsLayout);
sliderAdapter = new SliderAdapter(this);
mSlideViewPager.setAdapter(sliderAdapter);
addDotsIndicator(0);
mSlideViewPager.addOnPageChangeListener(viewListener);
myDialog = new Dialog(this);
}
public void addDotsIndicator(int position){
mDots = new TextView[8];
mDotLayout.removeAllViews();
for (int i= 0; i < mDots.length; i++){
mDots[i] = new TextView(this);
mDots[i].setText(Html.fromHtml("•"));
mDots[i].setTextSize(35);
mDots[i].setTextColor(getResources().getColor(R.color.colorTransparentWhite));
mDotLayout.addView(mDots[i]);
}
if (mDots.length > 0){
mDots[position].setTextColor(getResources().getColor(R.color.colorWhite));
}
}
ViewPager.OnPageChangeListener viewListener = new ViewPager.OnPageChangeListener(){
#Override
public void onPageScrolled(int position, float positionOffset, int positionOffsetPixels) {
}
#Override
public void onPageSelected (int i) {
switch (i) {
case 0: {
myDialog.show();
}
addDotsIndicator(i);
}
}
#Override
public void onPageScrollStateChanged(int state) {
}
};
public void ShowPopup(View v) {
TextView txtclose;
//Button btnFollow;
myDialog.setContentView(R.layout.pop_upfinal);
txtclose = myDialog.findViewById(R.id.txtclose);
txtclose.setText("X");
//btnFollow = (Button) myDialog.findViewById(R.id.btnfollow);
txtclose.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
myDialog.dismiss();
}
});
myDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
myDialog.show();
}
}
This class is an activity that on user swipe, the text and image from the buttons will change, even though their IDs will stay the same. (That's controlled by another class, it's working well).
Now, I wanted the image button on the activity do something different depending on which page is selected, and that's why there is a initial switch on the onPageSelected method, inside the Page change listener. The image button in the layout has the android:onClick="ShowPopup" tag, and I guess that also complicates things for me, if I wanted it to do something different in that same activity? Also, calling it that way on the switch, every time I change pages, and go back to the first one the popup window will open, since my call is explicit there. (As I said, even tough I found a way to somehow call my method, or at least it's result, it's not working as I expected).
Edit
I tried then changing it like this, so that the button wouldn't rely on the android:onClick="ShowPopup" Tag, and also wouldn't need to call a void method directly on the switch:
Added
public ImageButton popupchoice;
And also this to onCreate method:
popupchoice = this.findViewById(R.id.imgslide1);
Inside the switch I called it like this to get the button ID:
popupchoice.setOnClickListener(image1);
And set the View.OnClickListener like this:
View.OnClickListener image1 = new View.OnClickListener() {
public void onClick(View v) {
TextView txtclose;
//Button btnFollow;
myDialog.setContentView(R.layout.pop_upfinal);
txtclose = myDialog.findViewById(R.id.txtclose);
txtclose.setText("X");
//btnFollow = (Button) myDialog.findViewById(R.id.btnfollow);
txtclose.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
myDialog.dismiss();
}
});
myDialog.getWindow().setBackgroundDrawable(new ColorDrawable(Color.TRANSPARENT));
myDialog.show();
}
};
But that returns me:
java.lang.NullPointerException: Attempt to invoke virtual method 'void android.view.View.setOnClickListener(android.view.View$OnClickListener)' on a null object reference at .EscolhaAtendimento$1.onPageSelected(EscolhaAtendimento.java:81) Line 81 is the one inside the switch with the popupchoice.setOnClickListener(image1).
This error happens on page change, when coming back to the first Page, and also the button click won't work anymore.

I think you can use
EscolhaAtendimento.this.ShowPopup from inside your switch.

onBindViewHolder increase position onClickListener

I have an activity with two buttons Next and Previous and a textview, I would like to update the textview content each time I click Next or Back
For example, If I click Next the textview should show me content from the next position or vice versa.
I think that I should be using a loop but it gives me an error when I try to do that and when I add 1 to the position (i+1) it works but it only gives me the second position, I want to get all the positions not only the second one. I don't really know if my question is clear, Hope it is :)
onBindViewHolder
#Override
public void onBindViewHolder(#NonNull final MyViewHolder myViewHolder, #SuppressLint("RecyclerView") final int i) {
myViewHolder.cardView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
String nextContent = listItems.get(i).getContent();
String previousContent = listItems.get(i).getContent();
Intent intent = new Intent(v.getContext(), Main2Activity.class);
intent.putExtra("next", nextContent);
intent.putExtra("prev", previousContent);
v.getContext().startActivity(intent);
}
});
}
Main2Activity
btnNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
itemTextView.setText(nextContent);
}
});
btnPrev.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
itemTextView.setText(prevContent);
}
});

It's bad practice to set click listeners in the onBindViewHolder method.
Why? Because onBindViewHolder is called each time the views are recycled for the new content to be displayed on the screen. Say you have a list of 1000 elements with 10 of them visible on the screen.
You scroll it to the end => Then onBindViewHolder would be called 990 times => 990 click listeners set.
You also want to dodge costly operations in onBindViewHolder() because your scrolling would be potentially slowed down.
More tips here:
Recyclerview(Getting item on Recyclerview)

A loop isn't the answer here, a loop is for automating something. This is an event (the user interacted) so it's not suitable.
The algorithm you probably want is basically the following:
User clicked an item
Find out the item index
Increment the index
Find the item with that index (by asking the list)
If it exists, do something with it
However, the issue in the code you posted is that your 'nextContent' is always the current item. So you need the following change (but be careful about bounds):
String nextContent = listItems.get(i+1).getContent();
String previousContent = listItems.get(i-1).getContent();
You current code isn't using a loop, so the onBind method should be called once for each value of i so it should not always be the second item
After your comments it appears you have buttons unrelated to the list, so now what you need to do is make it so every time you click an item in the RV or a Next/Prev, you store the correct index (as you have no access to i)
In the activity:
private int currentTextItem = 0;
public void setCurrentTextItem(int i) {
currentTextItem = i;
//the dots here will be how you get the text from the item
// probably recyclerView.findViewHolderForAdapterPosition(pos)
myTextView.setText( ... );
}
In your view holder code:
myViewHolder.cardView.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
//(You should have some kind of call back from viewholder to activity)
activity.setCurrentTextItem(i);
}
});
Then your next/prev:
btnNext.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
setCurrentTextItem(currentTextItem + 1);
}
});
btnPrev.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
setCurrentTextItem(currentTextItem - 1);
}
});

Buttons outside the onCreate

Always in my apps I added buttons in void onCreate, but now I'm trying to do app with more buttons (about 10). I would like to all buttons active on start app.
In my opinion it is too much buttons to add in this onCreate and app will be starting to long.
I tried to put this:
myButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
myMethod();
}
})
out of onCreate
but AndroidStudio underlines setOnClickListener and view
I don't have ideas, how and where can i add button out of onCreate.

If you don't want to overcrowd your oncreate method, then create a clicklistener outside onCreate anywhere in activity and in onCreate just set it.
onCreate :
edit_a_member = (Button) findViewById(R.id.edit_member);
delete_a_member = (Button) findViewById(R.id.delete_member);
edit_a_member.setOnClickListener(handleClick);
delete_a_member.setOnClickListener(handleClick);
clickListener:
private View.OnClickListener handleClick = new View.OnClickListener() {
#Override
public void onClick(View view) {
switch (view.getId()) {
case R.id.edit_member:
member_selected = EDIT_MEMBER_SELECTED;
callDialog();
break;
case R.id.delete_member:
callDeleteAlert();
break;
}
}
};

You can simply add a separate method for your buttons in the same class, e.g.:
public void onCreate(...){
//Standard setup of views or whatever you want to do here
this.addButtons();
}
private void addButtons(){
Button b1 = new Button("Hi");
b1.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
myMethod();
}
});
Button b2 = new Button("Hi to you too");
b2.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
myMethod();
}
});
}
This is an example. You can do this in soooo many ways. I feel like you should thoroughly learn Java's fundamental Object Oriented programming, because that's really what your question suggests you don't understand. Go follow a youtube tutorial. I always like "The New Boston"'s Java tutorial series on youtube.
PS: You can make code like this beautiful under the 'Words of wisdom': Don't repeat yourself

If you have to do a lot of work in your onCreate but you are worried that the UI will take too long to load you can always post a delayed runnable to a handler so in the onCreate method put :
new Handler().postDelayed(new Runnable() {
#Override
public void run() {
//add your code here
}
},10);
what this will do is your UI will load then the code in your Runnable will be executed 10 milliseconds after your UI loads thus your app will not take too long to load the UI, even though in your case I doubt it would be necessary.

If you are declaring the buttons in xml file :
Add these properties in each button Declaration in your Xml :
android:clickable="true"
android:onClick="onClick"
And now in Activity Class create a method like this :
public void onClick(View v){
switch(v.getId){
case R.id.{buttons_id_in_xml}
(Your Code)
break;
(Like for others)
}
}
If you want to add buttons dynamically :
Create a method to add the button like this:
void addButton(String buttonName, int button id){
Button button = new Button(this);
button.setText("Push Me");
(add it to parent Layout of xml)
button.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
switch(id){
case id1:
(handle )
break;
(like for others)
}
}
});
}

The best way to do this is:
add implements View.OnClickListener to
public class MainActivity extends AppCompatActivity implements View.OnClickListener {
// declare variables
private Button mBtn1;
private Button mBtn2;
#Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_start);
// make an instance to the btns
mBtn1 = findViewById(R.id.btn1);
mBtn2 = findViewById(R.id.btn2);
// set onClickListener
mBtn1.setOnClickListener(this); // with "this" you are passing the view
mBtn2.setOnClickListener(this);
}
// implement onClick
#Override
public void onClick(View view) {
// check which btn was clicked by id
switch (view.getId()) {
case R.id.btn1:
btn1Clicked();
break;
case R.id.btn2:
btn2Clicked();
break;
}
}
private void btn1Clicked() {
// your code btn1 clicked
}
private void btn2Clicked() {
// your code btn2 clicked
}
Hope this helped. Cheers!

How attach two Click Listener in a button in android?

I want to attach two click listener in a button and both onclicklistener should be different. Is there any way to do this.? Can't use function to call from first to second. When I use this then I got output from second one only. I want both output.
I am working on some screening task, so whenever a use click on a button it tell me that user clicked on this in Logcat and also button do its normal task.
First is :
Button btn = (Button) findViewById(R.id.button1);
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
Log.i("First Click" , "Clicked on button 1");
}
});
Second is :
btn.setOnClickListener(new View.OnClickListener() {
public void onClick(View v2) {
if (v2 instanceof Button) {
Log.i("User Clicked a checkbox with value ", " : " + ((Button) v2).getText().toString());
}
}
});

You can't do that. Setting your second OnClickListener removes the first one.
That's why the function is called setOnClickListener() instead of addOnClickListener()
As you say, you can call two functions from the onClick()
Edit:
On your edit, you say that you want to show a message when your button is clicked.
You can add the loggging functionality that you need before doing anything else on the event, simply doing
#Override
public void onClick(View v) {
// Log something
// Your functionality
}
Or you can create a class implementing View.OnClickListener
public class MyOnClickListener implements View.OnClickListener {
#Override
public void onClick(View v) {
// Log something
}
}
And then, on your Activity:
btn.setOnClickListener(new MyOnClickListener() {
#Override
public void onClick(View v) {
super.onClick(v);
// Your functionality
}
});

You can use function in OnClickListener like-
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
run1();
run2();
}
});
private void run1(){
//Your first functionality
}
private void run2(){
//Your second functionality
}

If I understood you correctly, you could do this:
btn.setOnClickListener(new View.OnClickListener() {
#Override
public void onClick(View v) {
dothings(); //what you are trying to achieve with this button click
showViewInLogCat(v); //to show you the view in the logcat
}
}
where showViewInLogCat() is a function that show you which view was clicked in your logcat:
public void showViewInLogCat(View view) {
if (view instanceof Button) {
Log.i("User Clicked a checkbox with value ", " : " + ((Button) view).getText().toString());
}
//and add the other if
}
You can call this function in every OnClick event on other views

Probably if you want to do something like this..!
btn.setOnClickListener(new View.OnClickListener()
{
#Override
public void onClick(View v) {
Log.i("First Click" , "Clicked on button 1");
// add a boolean here to check if you want to do the task or not.
doTask = true;
doGeneralTask(doTask); //to show you the view in the logcat
}
}
and in doGeneralTask(doTask) do something like this.
public void doGeneralTask(boolean doTask) {
if (doTask) {
// do whatever generalized tasks you need.
}
}

Android Notification Area Customization

I don't know whether this question get minus points, but I searched every where and my last resort is stackoverflow.
I need to add five buttons to notification area in horizontally. And each button I need to add even listener. I know it is possible to do with RemoteViews. But I never seen anyone adding event listener to each element.
These are the references if anyone need to refer.
Notifications Documentation
How to create a custom notification on android
SlidingDrawer API

You can add 5 anonymous listeners, or a single named listener.
Anonymous:
Button b1 = new Button(...);
b1.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// first listener's code goes here
}
});
Button b2 = new Button(...);
b2.setOnClickListener(new View.OnClickListener() {
public void onClick(View v) {
// second listener's code goes here
}
});
...
named is much the same, but contains a switch statement to differentiate what happens:
View.OnClickListener myListener = new View.OnClickListener() {
public void onClick(View v) {
String buttonTitle = ((Button)v).getText();
if ("title1".equals(buttonTitle)) {
// do things for the first button's click
} else if ("title2".equals(buttonTitle)) {
// do things for the second button's click
}
...
}
});
...