How to change an image dynamically when a button is pressed and save the state of that image

Question

I have a problem where I need to alter an image of a imageView when the Button is pressed and when it is pressed again change to the image that was previously. I even managed to do this through the setBackgroundResource, the problem is when I close the app or get out of this determined Activity and I go back to her the image returns to be the one that was in android:background from the start. Can someone help me?

Xml code

<Button
    android:id="@+id/buttonLigarDesligar"
    android:padding="10dp"
    android:layout_width="40dp"
    android:layout_height="40dp"
    android:background="@drawable/icone_ligar"/>


<ImageView
    android:id="@+id/imgStatus"
    android:padding="10dp"
    android:background="@drawable/icone_vermelho"
    android:layout_width="40dp"
    android:layout_height="40dp"/>

Java code

buttonLigarDesligar.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {
            int status = 0;

            if (satus == 0){ 
                imgStatus.setBackgroundResource(R.drawable.ic_on);
                status = 1;
            }else{
                imgStatus.setBackgroundResource(R.drawable.icone_vermelho);
                status = 0;                   
            }
        }
    });
}

Answer 1

You can use Sharedpreferences to save user information to do the following:

First within your Activity declare:

private SharedPreferences sharedPreferences;
private boolean statusOff;
public static final String SHARED_PREFERENCES_USER = "user_preferences";
public static final String BUTTON_ON_OFF = "button_on_off";

Within the onCreate method add:

    sharedPreferences = this.getSharedPreferences(SHARED_PREFERENCES_USER, Context.MODE_PRIVATE);
    //Caso ainda não tenha sido criada essa preferência o retorno booleano
    //sera true, como destacado embaixo
    statusOff = sharedPreferences.getBoolean(BUTTON_ON_OFF, true);

Leave your button click event like this:

buttonLigarDesligar.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View view) {

                SharedPreferences.Editor editor = sharedPreferences.edit();

                if (statusOff) {
                    imgStatus.setBackgroundResource(R.drawable.ic_on);
                    //agora o valor do sharedpreferences é true, ou seja está ligado.
                    editor.putBoolean(BUTTON_ON_OFF, false);
                } else {
                    //caso o sharedpreference for false, então altera o icone pra vermelho e o valor
                    //booleano passa a ser true.
                    imgStatus.setBackgroundResource(R.drawable.icone_vermelho);
                    editor.putBoolean(BUTTON_ON_OFF, true);
                }
                editor.apply();
            }
        });

Within your Activity rewrite the onResume method as follows:

@Override
protected void onResume() {
    super.onResume();
    //Para quando a aplicação, for pausada ou parada, o método onResume checará
    //o status do botão que está salvo e caso ele seja "false" então altera
    //o seu background para o ic_on. Caso statusOff seja "true", não tem necessidade
    //de alteração já que você definiu por padrão no xml "icone_vermelho"
    if (!statusOff) {
        imgStatus.setBackgroundResource(R.drawable.ic_on);
    }
}

I hope I’ve helped.