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          自學(xué)鴻蒙應(yīng)用開發(fā)(7)- Picker組件

          本文介紹在鴻蒙應(yīng)用中Picker組件的基本用法。


          增加Picker組件

          如下代碼中46行~56行所示,在布局中增加Picker組件。

          <DirectionalLayout    xmlns:ohos="http://schemas.huawei.com/res/ohos"    ohos:height="match_parent"    ohos:width="match_parent"    ohos:orientation="vertical">    <Component        ohos:height="0vp"        ohos:weight="3"        ohos:width="match_parent"        />    <DirectionalLayout        xmlns:ohos="http://schemas.huawei.com/res/ohos"        ohos:height="match_content"        ohos:width="match_content"        ohos:layout_alignment="center"        ohos:orientation="vertical">        <Image            ohos:id="$+id:image"            ohos:width="match_content"            ohos:height="match_content"            ohos:layout_alignment="center"            ohos:image_src="$media:DevEco"        />        <TextField            ohos:id="$+id:text_field"            ohos:width="match_parent"            ohos:height="30vp"            ohos:text_size="20fp"            ohos:text_alignment="center"            ohos:hint="Please input text and press [Click me!] button."            ohos:background_element="$graphic:background_text_field"        />        <Button            ohos:id="$+id:hello_button"            ohos:width="match_content"            ohos:height="match_content"            ohos:text_size="27fp"            ohos:text="Click me!"            ohos:layout_alignment="center"            ohos:background_element="$graphic:background_button"            ohos:margin="15vp"            ohos:right_padding="8vp"            ohos:left_padding="8vp"            />        <Picker            ohos:id="$+id:test_picker"            ohos:height="match_content"            ohos:width="300vp"            ohos:min_value="0"            ohos:max_value="6"            ohos:wheel_mode_enabled="true"            ohos:background_element="#E1FFFF"            ohos:layout_alignment="horizontal_center"            ohos:normal_text_size="16fp"            ohos:selected_text_size="32fp"/>    DirectionalLayout>    <Component        ohos:height="0vp"        ohos:weight="5"        ohos:width="match_parent"        />DirectionalLayout>

          代碼中組件id被指定為test_picker,會(huì)在下面的響應(yīng)代碼中用到。


          獲取Picker組件設(shè)定和取得表示信息

          如下面代碼中30行和36行所示,在獲取PIcker組件后,設(shè)定表示信息并在動(dòng)作響應(yīng)代碼將最新表示信息設(shè)定到TextField組件上

          package com.example.helloharmony.slice;import com.example.helloharmony.ResourceTable;import ohos.aafwk.ability.AbilitySlice;import ohos.aafwk.content.Intent;import ohos.agp.components.Button;import ohos.agp.components.Component;import ohos.agp.components.Picker;import ohos.agp.components.TextField;import ohos.agp.utils.LayoutAlignment;import ohos.agp.window.dialog.ToastDialog;
          public class ComponentAbilitySlice extends AbilitySlice { @Override public void onStart(Intent intent) { super.onStart(intent); super.setUIContent(ResourceTable.Layout_ability_component); //獲取textfield輸入組件 TextField tf = (TextField) findComponentById(ResourceTable.Id_text_field); //獲取button組件 Button button = (Button) findComponentById(ResourceTable.Id_hello_button); // 為按鈕設(shè)置點(diǎn)擊事件回調(diào) button.setClickedListener(new Component.ClickedListener() { public void onClick(Component v) { new ToastDialog(getContext()) .setText(tf.getText()) .show(); } }); //獲取picker組件 Picker picker = (Picker) findComponentById(ResourceTable.Id_test_picker); //設(shè)定表示文字 picker.setDisplayedData(new String[]{"Mon", "Tue", "Wed", "Thu", "Fri", "Sat", "Sun"}); //設(shè)定事件響應(yīng) picker.setValueChangedListener((picker1, oldVal, newVal) -> { tf.setText(picker1.getDisplayedData()[newVal - picker1.getMinValue()]); }); } @Override public void onActive() { super.onActive(); } @Override public void onForeground(Intent intent) { super.onForeground(intent); }}

          畫面顯示如下:


          參考文檔

          Picker類:

          https://developer.harmonyos.com/cn/docs/documentation/doc-references/picker-0000001054119976

          Picker組件:

          https://developer.harmonyos.com/cn/docs/documentation/doc-guides/ui-java-component-picker-0000001059807909


          新書介紹

          《實(shí)戰(zhàn)Python設(shè)計(jì)模式》是作者最近出版的新書,拜托多多關(guān)注!

          本書利用Python 的標(biāo)準(zhǔn)GUI 工具包tkinter,通過(guò)可執(zhí)行的示例對(duì)23 個(gè)設(shè)計(jì)模式逐個(gè)進(jìn)行說(shuō)明。這樣一方面可以使讀者了解真實(shí)的軟件開發(fā)工作中每個(gè)設(shè)計(jì)模式的運(yùn)用場(chǎng)景和想要解決的問(wèn)題;另一方面通過(guò)對(duì)這些問(wèn)題的解決過(guò)程進(jìn)行說(shuō)明,讓讀者明白在編寫代碼時(shí)如何判斷使用設(shè)計(jì)模式的利弊,并合理運(yùn)用設(shè)計(jì)模式。

          對(duì)設(shè)計(jì)模式感興趣而且希望隨學(xué)隨用的讀者通過(guò)本書可以快速跨越從理解到運(yùn)用的門檻;希望學(xué)習(xí)Python GUI 編程的讀者可以將本書中的示例作為設(shè)計(jì)和開發(fā)的參考;使用Python 語(yǔ)言進(jìn)行圖像分析、數(shù)據(jù)處理工作的讀者可以直接以本書中的示例為基礎(chǔ),迅速構(gòu)建自己的系統(tǒng)架構(gòu)。




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