BlackBerry - 从 changeListener 事件中设置编辑字段的文本宽度

Question

如果input.getText()返回的长度大于 13，则用户输入的最后一个字符不应出现在编辑字段中。如果第 13 个字符是"，"，则程序应允许在"，"之后增加 2 个字符。这样，编辑字段的最大长度将为 16。

像这样限制编辑字段的文本宽度的选项是什么？

input = new BorderedEditField();
input.setChangeListener(new FieldChangeListener() {             
    public void fieldChanged(Field field, int context) {
        if(input.getText().length() < 13)
            input.setText(pruebaTexto(input.getText()));
        else
            //do not add the new character to the EditField
    }
});
public static String pruebaTexto(String r){
    return r+"0";
}

Answer 1

我已经编写了一个简单的BorderedEditField类来扩展EditField。修改此类的方法protected boolean keyChar(char key, int status, int time)，以便可以操作EditField的默认行为。如果您发现此示例很有帮助，则可以改进实现。

import net.rim.device.api.system.Characters;
import net.rim.device.api.ui.component.EditField;
import net.rim.device.api.ui.container.MainScreen;
public final class MyScreen extends MainScreen {
    public MyScreen() {
        BorderedEditField ef = new BorderedEditField();
        ef.setLabel("Label: ");
        add(ef);
    }
}
class BorderedEditField extends EditField {
    private static final int MAX_LENGTH = 13;
    private static final int MAX_LENGTH_EXCEPTION = 16;
    private static final char SPECIAL_CHAR = ',';
    protected boolean keyChar(char key, int status, int time) {
        // Need to add more rules here according to your need.
        if (key == Characters.DELETE || key == Characters.BACKSPACE) {
            return super.keyChar(key, status, time);
        }
        int curTextLength = getText().length();
        if (curTextLength < MAX_LENGTH) {
            return super.keyChar(key, status, time);
        }
        if (curTextLength == MAX_LENGTH) {
            char spChar = getText().charAt(MAX_LENGTH - 1);
            return (spChar == SPECIAL_CHAR) ? super.keyChar(key, status, time) : false;
        }
        if (curTextLength > MAX_LENGTH && curTextLength < MAX_LENGTH_EXCEPTION) {
            return super.keyChar(key, status, time);
        } else {
            return false;
        }
    }
}