我为我的问题准备了一个非常简短的测试用例(如下)。
单击按钮时,我想在新屏幕中显示字符串列表。
用户选择列表中的一项后,应再次显示上一屏幕,并且按钮标签应设置为所选字符串。
我的两个问题是:
- 从菜单内部我不知道如何弹出当前显示的屏幕
- 如何将所选项目从一个屏幕传递到另一个屏幕(假设我不想在前一个屏幕上引入公共变量/方法作为解决方法)
请建议我进行必要的更改src\mypackage\MyList.java:
package mypackage;
import java.util.*;
import net.rim.device.api.collection.*;
import net.rim.device.api.collection.util.*;
import net.rim.device.api.system.*;
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.util.*;
import net.rim.device.internal.i18n.*;
public class MyList extends UiApplication implements FieldChangeListener {
MyScreen myScreen = new MyScreen();
public static void main(String args[]) {
MyList app = new MyList();
app.enterEventDispatcher();
}
public MyList() {
MainScreen titleScreen = new MainScreen();
titleScreen.setTitle("Click the button:");
// TODO change the label of this button (see below)
ButtonField myButton = new ButtonField("Show the list", ButtonField.CONSUME_CLICK);
myButton.setChangeListener(this);
titleScreen.add(myButton);
pushScreen(titleScreen);
}
public void fieldChanged(Field field, int context) {
pushScreen(myScreen);
}
}
class MyScreen extends MainScreen {
ObjectListField myList = new ObjectListField();
public MyScreen() {
setTitle("Select an item below:");
myList.set(new String[] { "Item 1", "Item 2", "Item 3", "Item 4", });
add(myList);
addMenuItem(myMenu);
}
private final MenuItem myMenu = new MenuItem("Select item", 0, 0) {
public void run() {
int index = myList.getSelectedIndex();
if (index < 0)
return;
String item = (String) myList.get(myList, index);
Status.show("Selected: " + item);
// TODO how to return to the previous screen here?
// TODO how to call myButton.setLabel(item) here?
}
};
}
谢谢你!
亚历克斯
使用回调模式:
class TitleScreen extends MainScreen {
private ButtonField myButton;
public TitleScreen() {
super();
setTitle("Click the button:");
// TODO change the label of this button (see below)
myButton = new ButtonField("Show the list", ButtonField.CONSUME_CLICK);
myButton.setChangeListener(new FieldChangeListener() {
public void fieldChanged(Field field, int context) {
OnItemSelectedCallback callback =
new OnItemSelectedCallback() {
public void onItemSelected(String label) {
TitleScreen.this.onItemSelected(label);
}
};
MyScreen myScreen = new MyScreen(callback);
UiApplication.getUiApplication().pushScreen(myScreen);
}
});
add(myButton);
}
private void onItemSelected(String label) {
// this will be called when a menu item is executed on the MyScreen
// e.g. you can call smth like: myButton.setLabel(label);
}
}
interface OnItemSelectedCallback {
void onItemSelected(String label);
}
class MyScreen extends MainScreen {
ObjectListField myList = new ObjectListField();
private final OnItemSelectedCallback onItemSelectedCallback;
public MyScreen(OnItemSelectedCallback onItemSelectedCallback) {
setTitle("Select an item below:");
this.onItemSelectedCallback = onItemSelectedCallback;
myList.set(new String[] { "Item 1", "Item 2", "Item 3", "Item 4", });
add(myList);
addMenuItem(myMenu);
}
private final MenuItem myMenu = new MenuItem("Select item", 0, 0) {
public void run() {
int index = myList.getSelectedIndex();
if (index < 0)
return;
String item = (String) myList.get(myList, index);
Status.show("Selected: " + item);
// TODO how to return to the previous screen here?
// TODO how to call myButton.setLabel(item) here?
// notify the parent screen
onItemSelectedCallback.onItemSelected(item);
// close the current screen
UiApplication.getUiApplication().popScreen(MyScreen.this);
}
};
}
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