Question

我为应用程序做了一个简单的侧面菜单。首次调用菜单时。菜单显示正常。

第二次重新调用菜单时，我会看到一个空白屏幕。

这是我构建菜单的方式：

package com.mainsys.zappeion;


import static com.codename1.ui.CN.*;
import com.codename1.ui.Form;
import com.codename1.ui.Dialog;
import com.codename1.ui.plaf.UIManager;
import com.codename1.ui.util.Resources;
import com.codename1.io.Log;
import com.codename1.ui.Toolbar;
import com.codename1.ui.FontImage;

/**
 * This file was generated by <a href="https://www.codenameone.com/">Codename One</a> for the purpose 
 * of building native mobile applications using Java.
 */
public class Zappeion {

    private Form current;
    private Resources theme;

    public void init(Object context) {
        // use two network threads instead of one
        updateNetworkThreadCount(2);

        theme = UIManager.initFirstTheme("/theme");

        // Enable Toolbar on all Forms by default
        Toolbar.setGlobalToolbar(true);

        // Pro only feature
        Log.bindCrashProtection(true);

        addNetworkErrorListener(err -> {
            // prevent the event from propagating
            err.consume();
            if(err.getError() != null) {
                Log.e(err.getError());
            }
            Log.sendLogAsync();
            Dialog.show("Connection Error", "There was a networking error in the connection to " + err.getConnectionRequest().getUrl(), "OK", null);
        });        
    }

    public void start() {

        if(current != null){
            current.show();
            return;
        }

        Toolbar tb =    new Toolbar();

        Statues statues = new Statues();
        statues.setToolbar(tb);
        tb.addMaterialCommandToSideMenu("Αγάλματα", FontImage.MATERIAL_ALBUM, e -> { 
            statues.show();              
        });
        Sights sights = new Sights();
        sights.setToolbar(tb);
        tb.addMaterialCommandToSideMenu("Αξιοθέατα", FontImage.MATERIAL_ALBUM, e -> { 
            sights.show();              
        });
       Map map  = new Map();
       map.setToolbar(tb);
       tb.addMaterialCommandToSideMenu("Χάρτης ", FontImage.MATERIAL_ALBUM, e -> { 
            map.show();              
        });

        MainSys mns = new MainSys();
        mns.setToolbar(tb);
        SplashScreen sc = new SplashScreen(); //(sights, mns);
        sc.setToolbar(tb);
        sc.show();
    }

    public void stop() {
        current = getCurrentForm();
        if(current instanceof Dialog) {
            ((Dialog)current).dispose();
            current = getCurrentForm();
        }
    }

    public void destroy() {
    }

}

在上面的代码上，例如，如果我在菜单上单击“景点表格”，它将显示确定。如果然后我重新单击此菜单，将得到一个空白屏幕，没有菜单工具栏，什么也没有。

感谢您的帮助。

Answer 1

Toolbar是一个组件，它只能有一个父对象，并且已将其添加到3。我想控制台中会抛出一个异常来表明这一点。由于Toolbar的独特性质，有可能未引发异常。

我建议您不要创建工具栏，而应使用form.getToolbar();，尤其是因为您的代码已经声明了Toolbar.setGlobalToolbar(true);。

Answer 2

它的实际作用是下面的代码。我不知道它为什么起作用，因为从我看来，只是对代码的重新排序。我还改变了一个想法，就是我下载了新闻皮肤（Galaxy S8，ipone 8 plus）并对其进行了测试。但是之后，它可以在我以前的皮肤上工作（三星s7，iphone 6）。很奇怪，我不知道是否有人看到更多东西。

package com.mainsys.zappeion;


import static com.codename1.ui.CN.*;
import com.codename1.ui.Form;
import com.codename1.ui.Dialog;
import com.codename1.ui.plaf.UIManager;
import com.codename1.ui.util.Resources;
import com.codename1.io.Log;
import com.codename1.ui.Toolbar;
import com.codename1.ui.FontImage;

/**
 * This file was generated by <a href="https://www.codenameone.com/">Codename One</a> for the purpose 
 * of building native mobile applications using Java.
 */
public class Zappeion {

    private Form current;
    private Resources theme;

    public void init(Object context) {
        // use two network threads instead of one
        updateNetworkThreadCount(2);

        theme = UIManager.initFirstTheme("/theme");

        // Enable Toolbar on all Forms by default
        Toolbar.setGlobalToolbar(true);

        // Pro only feature
        Log.bindCrashProtection(true);

        addNetworkErrorListener(err -> {
            // prevent the event from propagating
            err.consume();
            if(err.getError() != null) {
                Log.e(err.getError());
            }
            Log.sendLogAsync();
            Dialog.show("Connection Error", "There was a networking error in the connection to " + err.getConnectionRequest().getUrl(), "OK", null);
        });        
    }

    public void start() {

        if(current != null){
            current.show();
            return;
        }        

        Statues statues = new Statues();
        Sights sights = new Sights();
        Map map  = new Map();
        MainSys mns = new MainSys();
        SplashScreen sc = new SplashScreen(sights, mns);
        BrowserForm browser = new BrowserForm();

        Toolbar tb = statues.getToolbar();

        tb.addMaterialCommandToSideMenu("Αρχική", FontImage.MATERIAL_ALBUM, e -> { 
           sc.setTitle("Αρχική");
           sc.show();              
        });
        tb.addMaterialCommandToSideMenu("Αγάλματα", FontImage.MATERIAL_ALBUM, e -> { 
             statues.setTitle("Αγάλματα");
             statues.setUrl("https://www.zappeion.gr/el/statues");
             statues.show();              
        });

        tb.addMaterialCommandToSideMenu("Αξιοθέατα", FontImage.MATERIAL_ALBUM, e -> { 
            sights.show();              
        });


       tb.addMaterialCommandToSideMenu("Χάρτης ", FontImage.MATERIAL_ALBUM, e -> { 
            map.show();              
        });

        statues.setToolbar(tb);
        sights.setToolbar(tb);
        map.setToolbar(tb);
        mns.setToolbar(tb);
        sc.setToolbar(tb);
        sc.show();
    }

    public void stop() {
        current = getCurrentForm();
        if(current instanceof Dialog) {
            ((Dialog)current).dispose();
            current = getCurrentForm();
        }
    }

    public void destroy() {
    }

}

表单在第二次调用时未显示

2 个答案: