Change android:textColor with a spinner

Question

I managed to use a spinner in my code and wanted to change the textColor of a certain text in the MainActivity file trough that spinner, but he is located in another class file - Einstellungen. Is it possible to change the textColor in the current activity from another activity?

This is the main_activity.xml where I want to change text color:

<TextView
    android:id="@+id/speedtext"
    android:layout_width="match_parent"
    android:layout_height="wrap_content"
    android:layout_marginTop="180dp"
    android:gravity="center"
    android:singleLine="true"
    android:text="TEXT"
    android:textColor="@android:color/white"
    android:textSize="220sp" />

This is the Einstellungen activity:

public class Einstellungen extends AppCompatActivity {
    String[] names = {"Weiß", "Blau", "Rot"};
    String[] des = {"Weiß", "Blau", "Rot"};
    ArrayAdapter<String> adapter;
    Spinner spinner;
    TextView description;

    public Button button;

    public void init() {
        button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                Intent toy = new Intent(Einstellungen.this, MainActivity.class);
                startActivity(toy);
            }
        });
    }

    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_einstellungen);
        spinner = (Spinner) findViewById(R.id.spinner);
        description = (TextView) findViewById(R.id.text);
        adapter = new ArrayAdapter<String>(getApplicationContext(), android.R.layout.simple_list_item_1, names);
        spinner.setAdapter(adapter);
        spinner.setOnItemSelectedListener(new AdapterView.OnItemSelectedListener() {
            public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
                switch (i) {
                    case 0:
                        description.setText("" + des[i]);
                        MainActivity.speed.setTextColor(Color.WHITE);
                        break;
                    case 1:
                        description.setText("" + des[i]);
                        MainActivity.speed.setTextColor(Color.BLUE);
                        break;
                    case 2:
                        description.setText("" + des[i]);
                        MainActivity.speed.setTextColor(Color.RED);
                        break;

                }
            }

            public void onNothingSelected(AdapterView<?> adapterView) {

            }
        });
        init();
    }
}

MainActivity:

public class MainActivity extends AppCompatActivity  {

    LocationService myService;
    static boolean status;
    LocationManager locationManager;
    static TextView dist, time, speed;
    static long startTime, endTime;
    ImageView image;
    static ProgressDialog locate;
    static int p = 0;

    private ServiceConnection sc = new ServiceConnection() {
        public void onServiceConnected(ComponentName name, IBinder service) {
            LocationService.LocalBinder binder = (LocationService.LocalBinder) service;
            myService = binder.getService();
            status = true;
        }

        public void onServiceDisconnected(ComponentName name) {
            status = false;
        }
    };

    public Button button;
    public void init() {
        button = (Button) findViewById(R.id.button);
        button.setOnClickListener(new View.OnClickListener() {

            public void onClick(View v) {
                Intent toy = new Intent(MainActivity.this, Einstellungen.class);
                startActivity(toy);
            }
        });
    }

    void bindService() {
        if (status == true)
            return;
        Intent i = new Intent(getApplicationContext(), LocationService.class);
        bindService(i, sc, BIND_AUTO_CREATE);
        status = true;
        startTime = System.currentTimeMillis();
    }

    void unbindService() {
        if (status == false)
            return;
        Intent i = new Intent(getApplicationContext(), LocationService.class);
        unbindService(sc);
        status = false;
    }

    protected void onResume() {
        super.onResume();

    }

    protected void onStart() {
        super.onStart();

    }

    protected void onDestroy() {
        super.onDestroy();
        if (status == true)
            unbindService();
    }

    public void onBackPressed() {
        if (status == false)
            super.onBackPressed();
        else
            moveTaskToBack(true);
    }

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

        speed = (TextView) findViewById(R.id.speedtext);
        image = (ImageView) findViewById(R.id.image);
        start();
        init();
    }

    public void start() {
        checkGps();
        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

        if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {

            return;
        }


        if (status == false)
            bindService();
        locate = new ProgressDialog(MainActivity.this);
        locate.setIndeterminate(true);
        locate.setCancelable(false);
        locate.setMessage("Suche GPS-Signal");
        locate.show();
    }


    void checkGps() {
        locationManager = (LocationManager) getSystemService(LOCATION_SERVICE);

        if (!locationManager.isProviderEnabled(LocationManager.GPS_PROVIDER)) {


            showGPSDisabledAlertToUser();
        }
    }

    private void showGPSDisabledAlertToUser() {
        AlertDialog.Builder alertDialogBuilder = new AlertDialog.Builder(this);
        alertDialogBuilder.setMessage("Bitte GPS aktivieren")
                .setCancelable(false)
                .setPositiveButton("GPS aktivieren",
                        new DialogInterface.OnClickListener() {
                            public void onClick(DialogInterface dialog, int id) {
                                Intent callGPSSettingIntent = new Intent(
                                        android.provider.Settings.ACTION_LOCATION_SOURCE_SETTINGS);
                                startActivity(callGPSSettingIntent);
                            }
                        });
        alertDialogBuilder.setNegativeButton("Abbrechen",
                new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        dialog.cancel();
                    }
                });
        AlertDialog alert = alertDialogBuilder.create();
        alert.show();
    }
}

Answer 1

First of all, please, never store View's into the static field, it leads to Memory leaks. Change:

static ProgressDialog locate;
static TextView dist, time, speed;

to

private ProgressDialog locate;
private TextView dist, time, speed;

Then, for your purposes, you can use SharedPreferences. Let's make it step by step.

1. Add the next fields to Einstellungen:

   public static final String SHARED_PREFERENCES = "SHARED_PREFS";
   public static final String SELECTED_COLOR = "SELECTED_COLOR";
   private SharedPreferences preferences;
   

2. Get SharedPreferences inside onCreate() method:

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_einstellungen);
       preferences = getSharedPreferences(SHARED_PREFERENCES, MODE_PRIVATE);
       ...
   }
   

3. Put selected color to SharedPreferences:

   @Override
   public void onItemSelected(AdapterView<?> adapterView, View view, int i, long l) {
       switch (i) {
           case 0:
               description.setText(des[i]);
               preferences.edit().putInt(SELECTED_COLOR, Color.WHITE).apply();
               break;
           case 1:
               description.setText(des[i]);
               preferences.edit().putInt(SELECTED_COLOR, Color.BLUE).apply();
               break;
           case 2:
               description.setText(des[i]);
               preferences.edit().putInt(SELECTED_COLOR, Color.RED).apply();
               break;
   
       }
   }
   

In your MainActivity:

1. Add the next field:

   private SharedPreferences preferences;
   

2. Inside onCreate() method, get selected color and set it to TextView:

   @Override
   protected void onCreate(Bundle savedInstanceState) {
       super.onCreate(savedInstanceState);
       setContentView(R.layout.activity_main);
   
       speed = findViewById(R.id.speedtext);
       image = findViewById(R.id.image);
   
       preferences = getSharedPreferences(Einstellungen.SHARED_PREFERENCES, MODE_PRIVATE);
       int color = preferences.getInt(Einstellungen.SELECTED_COLOR, Color.WHITE);
       speed.setTextColor(color);
       init();
   }
   

Update:
If you want to save spinner state, you can also use SharedPreferences:

1. Add another one constant to Einstellungen:

   public static final String SELECTED_COLOR_POSITION = "SELECTED_COLOR_POSITION";
   

2. Add the next line at the beginning of your onItemSelected() method, to save selected item position:

   preferences.edit().putInt(SELECTED_COLOR_POSITION, i).apply();
   

3. Restore state of the spinner in the onCreate() method, after spinner.setAdapter(adapter) line:

   int position = preferences.getInt(SELECTED_COLOR_POSITION, 0);
   spinner.setSelection(position);