How to change the color of a button in android using JAVA?

Question

I am working on a ANDROID project and in it I have multiple buttons.

REQUIREMENT:-

1.When I click on a button once I want it to change to green color and when I click on same button again I want it to change back to original color .

2.When a button is selected(ie color becomes GREEN) I want to add a number to a array list and when I select it once again I want to remove the added number from the list.

I have come up with this solution as of now. But it doesn't work.

int flag=1;
button1.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                flag+=1;
                if(flag%2==0) {
                    SeatArrayList.remove(Integer.valueOf(1));
                    button1.setBackgroundColor(Color.GREEN);
                }
                else{
                    SeatArrayList.add(1);
                    button1.setBackgroundColor(bg_yellow);
                }
            }
        });
button3.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                flag+=1;
                if(flag%2==0) {
                    SeatArrayList.remove(Integer.valueOf(3));

                    button3.setBackgroundColor(Color.GREEN);
                }
                else{
                    SeatArrayList.add(3);
                    button3.setBackgroundColor(bg_yellow);
                }
            }
        });
button4.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {
                flag+=1;
                if(flag%2==0) {
                    SeatArrayList.remove(Integer.valueOf(4));
                    button4.setBackgroundColor(Color.GREEN);
                }
                else{
                    SeatArrayList.add(4);
                    button4.setBackgroundColor(bg_yellow);
                }
            }
        });

Answer 1

You can easily manage this by using the boolean flag, here is one example for the same!

boolean isGreen = false;
button1.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View view) {
            if(isGreen){
                isGreen = false
                SeatArrayList.removeAt(SeatArrayList.size-1)
                button1.setBackgroundColor(Color.YELLOW);
            }else{
                isGreen = true
                SeatArrayList.add(1);
                button1.setBackgroundColor(Color.GREEN);
            }
        }
    });

Answer 2

You should create a flag for each button. I think that the following code does what you mention in the requirements:

1. XML File:

 <?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" xmlns:app="http://schemas.android.com/apk/res-auto" xmlns:tools="http://schemas.android.com/tools" android:layout_width="match_parent" android:layout_height="match_parent" android:orientation="vertical" tools:context=".MainActivity"> <Button android:id="@+id/btn1" android:layout_width="match_parent" android:layout_height="wrap_content" android:backgroundTint="@android:color/black" android:text="Button 1"> </Button> <Button android:id="@+id/btn2" android:layout_width="match_parent" android:layout_height="wrap_content" android:backgroundTint="@android:color/black" android:text="Button 2"> </Button> <Button android:id="@+id/btn3" android:layout_width="match_parent" android:layout_height="wrap_content" android:backgroundTint="@android:color/black" android:text="Button 3"> </Button> <TextView android:id="@+id/txtNumbers" android:layout_width="match_parent" android:layout_height="wrap_content" android:gravity="center" android:text="{ }" android:textSize="18sp"> </TextView> </LinearLayout>

2. MainActivity Java File:

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

private Button btn1, btn2, btn3;
private TextView txtNumbers;
private ArrayList<Integer> list;
private ArrayList<Boolean> isGreen;
private int initialColor;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    btn1 = (Button) findViewById(R.id.btn1);
    btn2 = (Button) findViewById(R.id.btn2);
    btn3 = (Button) findViewById(R.id.btn3);
    txtNumbers = (TextView) findViewById(R.id.txtNumbers);

    btn1.setOnClickListener(this);
    btn2.setOnClickListener(this);
    btn3.setOnClickListener(this);

    list = new ArrayList<>();
    isGreen = new ArrayList<>(Collections.nCopies(3, false));//Initialize values to false (In this case for only 3 buttons)
    initialColor = Color.BLACK;//The same color as in the XML file
}

@Override
public void onClick(View view) {
    switch (view.getId()) {
        case R.id.btn1:
            requirement(btn1, 0, 0);
            break;
        case R.id.btn2:
            requirement(btn2, 1, 1);
            break;
        case R.id.btn3:
            requirement(btn3, 2, 2);
            break;
    }
}

private void requirement(Button btn, int index, int number) {
    if (!isGreen.get(index)) {
        btn.setBackgroundColor(Color.GREEN);
        list.add(number);
        printList();
        isGreen.set(index, true);
    } else {
        btn.setBackgroundColor(initialColor);
        list.remove((Integer) number);//Cast to Integer, because this will eliminate the number by its value, not index
        printList();
        isGreen.set(index, false);
    }
}

private void printList() {
    String numbers = "{ ";
    for (int index = 0; index < list.size(); index++) {
        numbers += list.get(index) + ", ";
    }
    numbers += " }";
    txtNumbers.setText(numbers);
}

}

Result:

I hope it will be useful to you. I stay tuned, regards 😁/.