How to change activity background image using switch?

Question

I have two images (not colors) called black and white. I've written this code so far:

public class MainActivity extends AppCompatActivity
{
    View parentView;
    SwitchCompat switchCompat;

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

        switchCompat = findViewById(R.id.switchCompat);
        parentView = findViewById(R.id.parentView);

        SharedPreferences prefs = getSharedPreferences("save", MODE_PRIVATE);
        switchCompat.setChecked(prefs.getBoolean("value", false);
        
        switchCompat.setOnClickListener(view -> {
            if(switchCompat.isChecked()) {
               parentView.setImageResource(R.drawable.black);
               SharedPreferences.Editor ed = getSharedPreferences("save", MODE_PRIVATE);
               ed.putBoolean("value", true);
               ed.apply();
               switchCompat.setChecked(true);
            } else {
               parentView.setImageResource(R.drawable.white);
               SharedPreferences.Editor ed = getSharedPreferences("save", MODE_PRIVATE);
               ed.putBoolean("value", false);
               ed.apply();
               switchCompat.setChecked(false);
            }
        });
    }

Default background is white. As you see, if the user check switch on the background should be black, but this doesn't work. Do you know any solution?

Does this answer your question? [Android: checkbox listener](https://stackoverflow.com/questions/8386832/android-checkbox-listener) — cutiko, Nov 16 '21 at 17:46
Sorry, but no. I can save switch instance state but i cannot change background. — Wagner_91, Nov 16 '21 at 17:49
yes you can, is literally the answer someone gave you below, use `setOnCheckedChangeListener` instead of click listener — cutiko, Nov 16 '21 at 18:35

Sidharth Shambu · Accepted Answer · 2021-11-16T19:43:54.207

You needn't set the SwitchCompat if its changed, its redundant. Also SharedPreferences.Editor was initialized wrong. Try this

public class MainActivity extends AppCompatActivity implements CompoundButton.OnCheckedChangeListener {

    View parentView;
    SwitchCompat switchCompat;
    SharedPreferences prefs;

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

        switchCompat = findViewById(R.id.switchCompat);
        parentView = findViewById(R.id.parentView);

        prefs = getSharedPreferences("save", MODE_PRIVATE);
        switchCompat.setChecked(prefs.getBoolean("value", false));
        if (prefs.getBoolean("value", false)) { 
            parentView.setBackgroundResource(R.drawable.black);
         } else {
            parentView.setBackgroundResource(R.drawable.white);
         }
        switchCompat.setOnCheckedChangeListener(this);
    }

    @Override
    public void onCheckedChanged(CompoundButton buttonView, boolean isChecked) {
            if(buttonView.getId() == R.id.switchCompat) {
                if(isChecked) {
                  parentView.setImageResource(R.drawable.black);
                  SharedPreferences.Editor ed = prefs.edit();
                  ed.putBoolean("value", true);
                  ed.apply();
                } else {
                  parentView.setImageResource(R.drawable.white);
                  SharedPreferences.Editor ed = prefs.edit();
                  ed.putBoolean("value", false);
                  ed.apply();
                }
        }
    }
}

Thanks for answer. I tried this and I can change the background, but when I exit activity it doesn't save the background change. — Wagner_91, Nov 16 '21 at 18:42
You need to call `parentView.setImageResource(R.drawable.black);` or `parentView.setImageResource(R.drawable.white);` in `onCreate` based on `prefs.getBoolean("value", false)`. Add a check in `onCreate` with boolean from shared prefs and set black or white accordingly — Sidharth Shambu, Nov 16 '21 at 18:57
Do you think this? if (prefs.getBoolean("value", false)) { parentView.setBackgroundResource(R.drawable.white); } else { parentView.setBackgroundResource(R.drawable.black); } — Wagner_91, Nov 16 '21 at 19:18
I have updated this in the snippet above. It sets black if 'prefs.getBoolean("value", false)' returns true, else sets white. — Sidharth Shambu, Nov 16 '21 at 19:45

How to change activity background image using switch?

1 Answers1