How can I dynamically create menu items?

android, android-layout, android-menu, dynamic, menuitem

Solution

How to Dynamically Add Menu Items to an Android Activity

public class yourActivity extends Activity {
    ...
    private static final int MENU_ADD = Menu.FIRST;
    private static final int MENU_LIST = MENU.FIRST + 1;
    private static final int MENU_REFRESH = MENU.FIRST + 2;
    private static final int MENU_LOGIN = MENU.FIRST + 3;

    /**
     * Use if your menu is static (i.e. unchanging)
     */
    /*
    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        super.onCreateOptionsMenu(menu);
        menu.add(0, MENU_ADD, Menu.NONE, R.string.your-add-text).setIcon(R.drawable.your-add-icon);
        menu.add(0, MENU_LIST, Menu.NONE, R.string.your-list-text).setIcon(R.drawable.your-list-icon);
        menu.add(0, MENU_REFRESH, Menu.NONE, R.string.your-refresh-text).setIcon(R.drawable.your-refresh-icon);
        menu.add(0, MENU_LOGIN, Menu.NONE, R.string.your-login-text).setIcon(R.drawable.your-login-icon);
        return true;
    }
    */

    /**
     * Gets called every time the user presses the menu button.
     * Use if your menu is dynamic.
     */
    @Override
    public boolean onPrepareOptionsMenu(Menu menu) {
        menu.clear();
        if(enableAdd)
            menu.add(0, MENU_ADD, Menu.NONE, R.string.your-add-text).setIcon(R.drawable.your-add-icon);
        if(enableList)
            menu.add(0, MENU_LIST, Menu.NONE, R.string.your-list-text).setIcon(R.drawable.your-list-icon);
        if(enableRefresh)
            menu.add(0, MENU_REFRESH, Menu.NONE, R.string.your-refresh-text).setIcon(R.drawable.your-refresh-icon);
        if(enableLogin)
            menu.add(0, MENU_LOGIN, Menu.NONE, R.string.your-login-text).setIcon(R.drawable.your-login-icon);
        return super.onPrepareOptionsMenu(menu);
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        super.onOptionsItemSelected(item);

        switch (item.getItemId()) {
        case MENU_ADD: doAddStuff(); break;
        case MENU_LIST: doListStuff(); break;
        case MENU_REFRESH: doRefreshStuff(); break;
        case MENU_LOGIN: doLoginStuff(); break;
        }
        return false;
    }

The following specific example adds a MENU_LOGOUT option if the user is logged in.

    private static final int MENU_LOGOUT = MENU.FIRST + 4;

    public boolean onPrepareOptionsMenu(Menu menu) {
        ...
        if(auth.isLoggedIn()) {
            menu.add(0, MENU_LOGOUT, Menu.NONE, R.string.your-logout-text).setIcon(R.drawable.your-logout-icon);
        }
        ...
    }

    public boolean onOptionsItemSelected(MenuItem item) {
        ...
        case MENU_LOGOUT:
            if(auth.isLoggedIn()) {
                doLogout();
            } else {
                Toast.makeText(this, "You must have somehow been logged out between the time the menu button was pressed and now.", Toast.DURATION_LONG).show();
            }
            break;
        ...
    }

That's all there is to it.

Problem

I'm building an Android application and I'm trying to build a user management system where users can login, logout, etc. I want to display a login menu item if the user is logged out and a logout button if the user is logged in. How can I do this dynamically? This is the layout file right now: ``` <?xml version="1.0" encoding="utf-8"?> <menu xmlns:android="http://schemas.android.com/apk/res/android"> <item android:id="@+id/add" android:title="Add" android:icon="@drawable/ic_menu_add"/> <item android:id="@+id/list" android:title="List" android:icon="@drawable/ic_menu_list"/> <item android:id="@+id/refresh" android:title="Refresh" android:icon="@drawable/ic_menu_refresh"/> <item android:id="@+id/login" android:title="Login" android:icon="@drawable/ic_menu_login"/> </menu> ``` This is my Java right now: ``` @Override public boolean onCreateOptionsMenu(Menu menu) { new MenuInflater(this).inflate(R.menu.activity_main, menu); return(super.onCreateOptionsMenu(menu)); } @Override public boolean onOptionsItemSelected(MenuItem item) { System.out.println(item.getItemId()==R.id.add); if (item.getItemId()==R.id.add) { //Cannot add spot unless we have obtained the users current location. if((currentLat != 0) && (currentLng != 0)) { System.out.println("loggedin? : " + auth.isLoggedIn()); if(!auth.isLoggedIn()) { Toast.makeText(MainActivity.this, "You must be logged in to add a new spot", Toast.LENGTH_LONG).show(); } else { Intent addIntent = new Intent(MainActivity.this, AddSpot.class); Bundle b = new Bundle(); b.putDouble("currentLat", currentLat); b.putDouble("currentLng", currentLng); addIntent.putExtras(b); startActivity(addIntent); return(true); } } } else if(item.getItemId()==R.id.list) { //Pointless showing them a blank screen if nothing is retrieved from the server if(list != null) { Intent listIntent = new Intent(MainActivity.this, ListLocations.class); listIntent.putExtra("list", list); startActivity(listIntent); return(true); } } if(item.getItemId()==R.id.refresh) { finish(); startActivity(getIntent()); return(true); } if(item.getItemId()==R.id.login) { Intent loginIntent = new Intent(MainActivity.this, LoginActivity.class); startActivity(loginIntent); return(true); } return(super.onOptionsItemSelected(item)); } ```

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