根据条件更改ActionBar中的图标

Question

当用户按下图标时,我正在更新SQLite数据库中的记录ActionBar.正在更新的信息是一个标记,用于将记录添加到"收藏夹"页面.

问题

当用户将记录添加或删除到收藏夹时,我希望ActionBar更改中的图标.我有一个完整的星形图标和一个空的星形图标.

setIcon如果记录是收藏夹,则该方法显示完整的星形图标;如果记录不是收藏夹,则显示空星形图标.

在下面的代码中,您将看到我正在使用a boolean isInFavourite,这是true什么时候String fav = "y".

输入时Activity,icon显示正确.

当用户单击icon以调用onMenuItemClick()方法时,记录已成功更新,但icon不会更改.

我无法更改boolean isInFavourite记录更新的时间,因为Eclipse希望将所有变量设置为final

一旦记录更新,任何人都可以帮我改变图标.

@Override
public boolean onCreateOptionsMenu(Menu menu) {

    db = new DBHelper(this);
    db.createDataBase();
    db.openDataBase();


    Bundle bundle = getIntent().getExtras();
    final String rowid = bundle.getString("id");
    final String fav = bundle.getString("fav");

    //Boolean to check if record is a favourite
    final boolean isInFavourite = fav.contentEquals("y");

    menu.add("Add to Favourites")
            .setOnMenuItemClickListener(new OnMenuItemClickListener() {

                public boolean onMenuItemClick(MenuItem item) {

                    String toggle;
                    String message;

                    //Logic to add or remove row from recording.
                    if (isInFavourite) {
                        toggle = "n";
                        message = "Recipe removed from Favourites";
                    } else {
                        toggle = "y";
                        message = "Recipe added to Favourites";
                    }

                    //Update favourite record in database
                    db.updateFavourite(rowid, toggle);
                    db.close();

                    Toast.makeText(getApplicationContext(), message,
                            Toast.LENGTH_LONG).show();

                    return true;
                }

            })

            //Set icon depending on whether record is a favourite or not.
            .setIcon(isInFavourite ? R.drawable.fav_true : R.drawable.fav_false)
            .setShowAsAction(MenuItem.SHOW_AS_ACTION_IF_ROOM);

    return true;

}

感谢@dmon的解决方案

解

private DBHelper db = null;

public String fav = null;
public String rowid = null;
public boolean isFav;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);

    ...

    Bundle bundle = getIntent().getExtras();
    rowid = bundle.getString("id");
    fav = bundle.getString("fav");

    if (fav.contentEquals("y")) {
        isFav = true;
    } else {
        isFav = false;
    }


    try {
        db = new DBHelper(this);
        db.createDataBase();
    } catch (IOException e) {
        e.printStackTrace();
    }

}


@Override
public boolean onCreateOptionsMenu(Menu menu) {

    getSupportMenuInflater().inflate(R.menu.menu_settings, menu);

    return true;
}

@Override
public boolean onPrepareOptionsMenu(Menu menu) {
    MenuItem fave = menu.findItem(R.id.add);
    MenuItem unfave = menu.findItem(R.id.remove);

    fave.setVisible(isFav);
    unfave.setVisible(!isFav);

    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    switch (item.getItemId()) {
    case android.R.id.home:
        onBackPressed();
        return true;
    case R.id.add:
        fav = "n";
        isFav = false;
        updateFav();
        supportInvalidateOptionsMenu();
        Toast("Removed from Favourites");
        return true;
    case R.id.remove:
        fav = "y";
        isFav = true;
        updateFav();
        supportInvalidateOptionsMenu();
        Toast("Added to Favourites");
        return true;
    default:
        return super.onOptionsItemSelected(item);
    }
}

public void updateFav (){
        db.openDataBase();
        db.updateFavourite(rowid, fav);
        db.close();
}

XML文件:res/menu/menu_settings.xml

<?xml version="1.0" encoding="utf-8"?>
<menu xmlns:android="http://schemas.android.com/apk/res/android" >
<item
    android:id="@+id/add"
    android:icon="@drawable/good"
    android:showAsAction="always"
    />
<item
    android:id="@+id/remove"
    android:icon="@drawable/bad"
    android:showAsAction="always"/>

Answer 1

最简单的方法是只提供两个不同的按钮并相应地隐藏/显示它们:

@Override
public boolean onCreateOptionsMenu(Menu menu) {
  MenuInflater inf = new MenuInflater(this);
  inf.inflate(R.menu.menu_xml, menu);
  return true;
}

@Override
public boolean onPrepareOptionsMenu(Menu menu) {
  MenuItem fave = menu.findItem(R.id.favorite);
  MenuItem unfave = menu.findItem(R.id.unfavorite);

  fave.setVisible(!isFave);
  unfave.setVisible(isFave);
  return true;
}

然后在状态更改时使选项菜单无效.请注意,您必须拥有一个具有项目当前状态的全局变量(isFave来自哪里)

invalidateOptionsMenu();