黑莓:显示警报/状态/对话尽早退出

Question

假设我有一个典型的黑莓应用程序:

public class MyApp extends UiApplication {
    public static void main(String[] args) {
        MyApp app = new MyApp();
        app.enterEventDispatcher();
    }
    public MyApp() {
        pushScreen(new MyScreen());
    }    
}

并且在开始时我已经注意到，缺少一个强制条件(错误的显示尺寸;缺少SD卡;一些IT政策;等)

是否有一种方法来显示一个简短的和快速的消息给用户(在警报/状态/对话框/任何形式)，并直接退出-没有/之前实例化一个复杂的屏幕/注册加速监听器/安装复杂的cleanupunnable ?

我试过Status.show()， Dialog.alert() -他们不工作(RuntimeException "pushModalScreen被一个非事件线程调用"):

public class MyScreen extends MainScreen {
    public MyScreen() {
        if (Display.getWidth() < 400) {
            Status.show("Goodbye");
            return;
        }
    }
}

Answer 1

使用invokeLater代替直接调用。示例如下:

Application.getApplication().invokeLater(new Runnable() {
    public void run() {
        Dialog.inform("Your message here...");
    }
});

你可以用Status.show()来代替Dialog.inform

Answer 2

实际上下面是更好的，比拉斐尔的建议-因为它没有丑陋的白色屏幕下面。下面是我的完整示例MyApp.java:

import net.rim.device.api.ui.*;
import net.rim.device.api.ui.component.*;
import net.rim.device.api.ui.container.*;
import net.rim.device.api.ui.decor.*;
import net.rim.device.api.system.*;
import net.rim.device.api.ui.image.*;
public class MyApp extends UiApplication {
    public static void main(String[] args) {
        MyApp app = new MyApp();
        app.enterEventDispatcher();
    }
    public MyApp() {
        pushScreen(new MyScreen());
    }    
}
class MyScreen extends MainScreen implements DialogClosedListener {
    Dialog myDialog = new Dialog(Dialog.OK, "Goodbye!", 0, Bitmap.getPredefinedBitmap(Bitmap.EXCLAMATION), Dialog.GLOBAL_STATUS);
    public MyScreen() {
        // XXX just some condition, like wrong dimensions or IT policy
        if (Display.getWidth() > 40) {
            myDialog.setDialogClosedListener(this);
            Application.getApplication().requestBackground();
            Application.getApplication().invokeLater(new Runnable() {
                public void run() {
                    myDialog.show();
                }
            });
            return;
        }
        // XXX heavy stuff to be skipped
    }
    public void dialogClosed(Dialog dialog, int choice) {
        if (dialog == myDialog) {
            System.out.println("XXX exiting XXX");
            System.exit(1);
        }
    }
}