Question

我有10个扩展baseActivity的活动。我的BaseActivity基本上有一个帮助菜单图标。当用户按下帮助菜单图标时，我应该显示该活动的帮助菜单。如何知道哪个活动称为帮助菜单，以便我知道要显示哪个xml资源

public class BaseActivity extends Activity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.help_menu, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
            case R.id.help_menu_item:
                    displayHelpMenu();          
                return true;

            default:
                return super.onOptionsItemSelected(item);
        }
    }

    protected void displayHelpMenu(){

             // I will load the xml to the textview and display it in dialog. How can I know which xml resource to load

    }
}

Answer 1

查找Activity的一种方法是使用instanceOf。像这样：

protected void displayHelpMenu() {
    // I will load the xml to the textview and display it in dialog.
    // How can I know which xml resource to load

    if(this instanceOf DerivedActivity.class) {
        // load XML file
    }
    else if(...) {
    ...
    }
}

但是，在我看来，虽然这解决了你的问题，但这不是正确的做事方式。在最终出现这种情况的OOP中，您应该使用方法覆盖。

base class定义了加载资源的一般功能，而派生类应该提供要加载的文件的名称。换句话说，base class不应该知道derived class。更好的解决方案是：

protected void displayHelpMenu() {

    // ask each child class for the help menu resource file
    int resId = getHelpMenuResource();

    // write code to load XML file with resId
    ...
    ...
}

protected int getHelpMenuResource() {
    return defaultMenuId;
}

现在，在您的派生类中，@Override getHelpMenuResource()方法并返回特定于该活动的资源ID。

Answer 2

如何使您的BaseActivity抽象并添加getMenuResource方法？

public abstract class BaseActivity extends Activity {

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

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater inflater = getMenuInflater();
        inflater.inflate(R.menu.help_menu, menu);
        return true;
    }
    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle item selection
        switch (item.getItemId()) {
            case R.id.help_menu_item:
                    displayHelpMenu();          
                return true;

            default:
                return super.onOptionsItemSelected(item);
        } 
    }

    protected void displayHelpMenu(){

             // I will load the xml to the textview and display it in dialog. How can I know which xml resource to load
        int menuResourceId = getMenuResourceId();
        // do the rest
    }

    public abstract int getMenuResourceId();
}

如何知道哪个活动点击了按钮？

2 个答案: