3.9 Component Picker by HarmonyOS

Author: Han Ru

Company: Program Ka (Beijing) Technology Co., LTD

Hong Meng Bus columnist

The Picker provides a sliding selector that allows the user to select from a predefined range.

Supported XML attributes

The Picker’s common XML attribute inherits from: DirectionalLayout

The Picker’s own XML attributes are shown in the following table:

The attribute name	Product description	The values	The values that	Use case
element_padding	The spacing between the text and the Element Element must be configured through the setElementFormatter interface	A float	A float type representing spacing dimensions. They can be floating point values, which default to px; It can also be a floating point value with px/ VP /fp units; Float resources can also be referenced.	ohos:element_padding=”30″ ohos:element_padding=”16vp” ohos:element_padding=”$float:padding”
max_value	The maximum	The integer types	You can set integer values directly or refer to an INTEGER resource.	ohos:max_value=”10″ ohos:max_value=”$integer:value”
min_value	The minimum value	The integer types	You can set integer values directly or refer to an INTEGER resource.	ohos:min_value=”1″ ohos:min_value=”$integer:value”
value	The current value	The integer types	You can set integer values directly or refer to an INTEGER resource.	ohos:value=”5″ ohos:value=”$integer:value”
normal_text_color	Unselected text color	Color type	You can set the color value directly or reference the color resource.	ohos:normal_text_color=”#A8FFFFFF” ohos:normal_text_color=”$color:black”
normal_text_size	Deselect the selected text size	A float	A float type representing the font size. They can be floating point values, which default to px; It can also be a floating point value with px/ VP /fp units; Float resources can also be referenced.	ohos:normal_text_size=”30″ ohos:normal_text_size=”16fp” ohos:normal_text_size=”$float:size_value”
selected_text_color	The selected text color	Color type	You can set the color value directly or reference the color resource.	ohos:selected_text_color=”#A8FFFFFF” ohos:selected_text_color=”$color:black”
selected_text_size	Size of selected text	A float	A float type representing the font size. They can be floating point values, which default to px; It can also be a floating point value with px/ VP /fp units; Float resources can also be referenced.	ohos:selected_text_size=”30″ ohos:selected_text_size=”16fp” ohos:selected_text_size=”$float:size_value”
selector_item_num	The number of items displayed	The integer types	You can set integer values directly or refer to an INTEGER resource.	ohos:selector_item_num=”10″ ohos:selector_item_num=”$integer:num”
selected_normal_text_margin_ratio	Ratio of selected text margins to normal text margins	A float	Floating-point values can be set directly, or float floating-point resources can be referenced. The value ranges from >0.	Ohos: selected_normal_text_margin_ratio = “0.5” ohos:selected_normal_text_margin_ratio=”$float:ratio”
shader_color	Shader color	Color type	You can set the color value directly or reference the color resource.	ohos:shader_color=”#A8FFFFFF” ohos:shader_color=”$color:black”
top_line_element	The top row of the selected item	Element type	Can directly configure the color value, also can reference color resources or reference media/graphic image resources.	ohos:top_line_element=”#FFFFFFFF” ohos:top_line_element=” $color:black”<br />ohos:top_line_element=”$ media:media_src” ohos:top_line_element=”$graphic:graphic_src”
bottom_line_element	The bottom line of the selected item	Element type	Can directly configure the color value, also can reference color resources or reference media/graphic image resources.	ohos:bottom_line_element=”#FFFFFFFF” ohos:bottom_line_element=” $color:black”<br />ohos:bottom_line_element=”$ media:media_src” ohos:bottom_line_element=”$graphic:graphic_src”
wheel_mode_enabled	Select whether the wheel goes around	Boolean type	You can set true/false directly or refer to a Boolean resource.	ohos:wheel_mode_enabled=”true” ohos:wheel_mode_enabled=”$boolean:true”

Use Picker

Create Picker in XML

<Picker
        ohos:id="$+id:test_picker"
        ohos:height="match_content"
        ohos:width="300vp"
        ohos:background_element="#E1FFFF"
        ohos:layout_alignment="horizontal_center"
        ohos:normal_text_size="18fp"
        ohos:selected_text_size="20fp"/>
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Selector created:

In MainAbilitySlice. Java, set the Picker value range

 				Picker picker = (Picker) findComponentById(ResourceTable.Id_test_picker);
        picker.setMinValue(0); // Set the minimum value in the selector
        picker.setMaxValue(6); // Set the maximum value in the selector
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Operation effect:

3. Response to selector changes

				picker.setValueChangedListener((picker1, oldVal, newVal) -> {
            // oldVal: the last selected value; NewVal: the latest value selected
            new ToastDialog(getContext())
                    .setText("oldVal:"+oldVal+",newVal:"+newVal)
                    .show();
        });
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Here we pop up ToastDialog:

4. Format the Picker’s display

Using the Picker’s setFormatter Formatter method, the user can modify the string displayed in the Picker option to a specific format.

picker.setFormatter(i -> {
    String value;
    switch (i) {
        case 0:
            value = "Mon";
            break;
        case 1:
            value = "Tue";
            break;
        case 2:
            value = "Wed";
            break;
        case 3:
            value = "Thu";
            break;
        case 4:
            value = "Fri";
            break;
        case 5:
            value = "Sat";
            break;
        case 6:
            value = "Sun";
            break;
        default:
            value = "" + i;
    }
    return value;
});
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Format selector:

5. Set the string array to display

For components that do not display numbers directly, this method sets a one-to-one correspondence between strings and numbers. The string array length must be equal to the total number of values in the value range. When used, note that this method overrides the picker.setFormatter(Formatter Formatter) method.

In Java code:

				// Sets the array of strings to display, which overrides the picker.setformatter (Formatter Formatter) method.
        picker.setDisplayedData(new String[]{"Monday"."Tuesday"."Wednesday"."Thursday"."Friday"."Saturday"."Sunday"});
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Operation effect:

Third, style Settings

1. Text-related attributes

Set the text style in the XML file:

<Picker
    ...
    ohos:normal_text_color="#FFA500"
    ohos:selected_text_color="#00FFFF"/>
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Set text styles in Java code:

picker.setNormalTextFont(Font.DEFAULT_BOLD);
picker.setNormalTextSize(40);
picker.setNormalTextColor(new Color(Color.getIntColor("#FFA500")));
picker.setSelectedTextFont(Font.DEFAULT_BOLD);
picker.setSelectedTextSize(40);
picker.setSelectedTextColor(new Color(Color.getIntColor("#00FFFF")));
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After setting the style:

2. Set the top and bottom borders of the selected text

Set in XML:

<Picker
    ...
    ohos:bottom_line_element="#40E0D0"
    ohos:top_line_element="#40E0D0"/>
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Set this in Java code:

ShapeElement shape = new ShapeElement();
shape.setShape(ShapeElement.RECTANGLE);
shape.setRgbColor(RgbColor.fromArgbInt(0xFF40E0D0));
// Set the top border separately
// picker.setDisplayedLinesTopElement(shape); 
// Set the lower border separately
// picker.setDisplayedLinesBottomElement(shape);
// Set both the upper and lower borders
picker.setDisplayedLinesElements(shape, shape);
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Set the top and bottom border styles:

3. Set the ratio of the selected text margin in the Picker to the normal text margin

Set in the XML file:

<Picker
    ...
    ohos:selected_normal_text_margin_ratio="5.0">
</Picker>
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Set this in Java code:

picker.setSelectedNormalTextMarginRatio(5.0 f);
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The effect after setting the margin:

4. Set the selection wheel mode

This mode is used to determine whether the Picker displays data in a loop.

Set in the XML file:

<Picker
    ...
    ohos:wheel_mode_enabled="true"/>
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Set this in Java code:

picker.setWheelModeEnabled(true);
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The display after changing the selection wheel mode:

5. Set the Picker’s shader color

Set in the XML file:

<Picker
    ...
    ohos:shader_color="#1E90FF"/>
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Set this in Java code:

picker.setShaderColor(new Color(Color.getIntColor("#1E90FF")));
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The style after setting the shader color:

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3.9 Component Picker by HarmonyOS