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4. 以積木式編程製作網絡應用程式
迴圈
迴圈

本文件解釋了各種迴圈結構,用於重複操作、條件執行、遍歷範圍和數組以及終止迴圈。

多次重複操作

重複 4 次

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><block type=\"controls_repeat_ext\"><value name=\"TIMES\"><shadow type=\"math_whole_number\"><field name=\"NUM\">4</field></shadow></value></block></xml>"}

這用於多次執行某些操作。

參數: 條件:數字(預設值:4)
輸出: N/A
示例代碼:

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"controls_repeat_ext\"><value name=\"TIMES\"><shadow type=\"math_whole_number\"><field name=\"NUM\">4</field></shadow></value><statement name=\"DO\"><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"1\" _input_init=\"true\"></mutation><value name=\"text\"><shadow type=\"text\"><field name=\"TEXT\">Hello</field></shadow></value></block></value></block></statement></block></next></block></next></block></statement></block></xml>"}

輸出:

重複 4 次 - 輸出

在滿足布爾條件時執行操作

雖然是假的

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><block type=\"device_while\"><value name=\"COND\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">FALSE</field></shadow></value></block></xml>"}

此塊用於在滿足條件時運行相同的操作。

參數: 顯示設定:布爾值 (True/False [Default])
輸出: N/A
示例代碼:

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"device_while\"><value name=\"COND\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">FALSE</field></shadow></value><statement name=\"DO\"><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"1\" _input_init=\"true\"></mutation><value name=\"text\"><shadow type=\"text\"><field name=\"TEXT\">Showing text after 5 seconds.</field></shadow></value></block></value><next><block type=\"Task_sleep\"><value name=\"ms\"><shadow type=\"math_number\"><field name=\"NUM\">5000</field></shadow></value></block></next></block></statement></block></next></block></next></block></statement></block></xml>"}

雖然為 false,但輸出:

雖然 false do - 輸出

雖然為 true,但輸出:

雖然為 true do - 輸出

在從零到最終取值時執行操作

對於從 0 到 4 的索引

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><block type=\"controls_repeat_ext\"><value name=\"TIMES\"><shadow type=\"math_whole_number\"><field name=\"NUM\">4</field></shadow></value></block></xml>"}

此塊用於在將值從 0 取到最終數位時執行操作,該數位將乘以 1。

參數:

  • 指數
  • 條件:數字(預設值:4)

輸出: N/A
示例代碼:

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable><variable>index</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"pxt_controls_for\"><value name=\"VAR\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">index</field></shadow></value><value name=\"TO\"><shadow type=\"math_whole_number\"><field name=\"NUM\">4</field></shadow></value><statement name=\"DO\"><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"1\" _input_init=\"true\"></mutation><value name=\"text\"><shadow type=\"text\"><field name=\"TEXT\">It will repeat 5 times.</field></shadow></value></block></value></block></statement></block></next></block></next></block></statement></block></xml>"}

輸出:

對於從 0 到 4 的索引 - 輸出

在陣列長度中取值時執行操作

對於清單的元素值

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><block type=\"pxt_controls_for_of\"><value name=\"VAR\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">value</field></shadow></value><value name=\"LIST\"><shadow type=\"variables_get\"><field name=\"VAR\">list</field></shadow></value></block></xml>"}

此塊用於在陣列中逐個取值直到清單末尾時執行一些操作。

參數:

  • 陣列

輸出: N/A
示例代碼:

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable><variable>list</variable><variable>value</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"variables_set\"><field name=\"VAR\">list</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"lists_create_with\"><mutation items=\"3\" horizontalafter=\"3\"/><value name=\"ADD0\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow></value><value name=\"ADD1\"><shadow type=\"math_number\"><field name=\"NUM\">1</field></shadow></value><value name=\"ADD2\"><shadow type=\"math_number\"><field name=\"NUM\">2</field></shadow></value></block></value><next><block type=\"pxt_controls_for_of\"><value name=\"VAR\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">value</field></shadow></value><value name=\"LIST\"><block type=\"variables_get\"><field name=\"VAR\">list</field></block></value><statement name=\"DO\"><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"1\" _input_init=\"true\"></mutation><value name=\"text\"><shadow type=\"text\"><field name=\"TEXT\">It will repeat 3 times.</field></shadow></value></block></value></block></statement></block></next></block></next></block></next></block></statement></block></xml>"}

輸出:

對於清單的元素值 - 輸出

中斷循環

中斷

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><block type=\"break_keyword\"/></xml>"}

該模組用於停止中斷循環。

參數: N/A
輸出: N/A
示例代碼:

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"device_while\"><value name=\"COND\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">TRUE</field></shadow></value><statement name=\"DO\"><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"1\" _input_init=\"true\"></mutation><value name=\"text\"><shadow type=\"text\"><field name=\"TEXT\">It will show once only.</field></shadow></value></block></value><next><block type=\"break_keyword\"/></next></block></statement></block></next></block></next></block></statement></block></xml>"}

輸出:

中斷 - 輸出

執行下一步操作

繼續

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><block type=\"continue_keyword\"/></xml>"}

這用於跳過當前操作並繼續迴圈中的下一個操作。

參數: N/A
輸出: N/A
示例代碼:

{"blocks":"<xml xmlns=\"https://developers.google.com/blockly/xml\"><variables><variable>mainLayout</variable><variable>mainScreen</variable><variable>index</variable></variables><block type=\"pxt-on-start\" x=\"0\" y=\"0\"><statement name=\"HANDLER\"><block type=\"variables_set\"><field name=\"VAR\">mainLayout</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"ScreenItem_createLayout\"/></value><next><block type=\"variables_set\"><field name=\"VAR\">mainScreen</field><value name=\"VALUE\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"Screen_create\"><value name=\"label\"><shadow type=\"text\"><field name=\"TEXT\">Main</field></shadow></value><value name=\"layout\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value></block></value><next><block type=\"pxt_controls_for\"><value name=\"VAR\"><shadow type=\"variables_get_reporter\"><field name=\"VAR\">index</field></shadow></value><value name=\"TO\"><shadow type=\"math_whole_number\"><field name=\"NUM\">4</field></shadow></value><statement name=\"DO\"><block type=\"controls_if\"><value name=\"IF0\"><shadow type=\"logic_boolean\"><field name=\"BOOL\">TRUE</field></shadow><block type=\"logic_compare\"><field name=\"OP\">EQ</field><value name=\"A\"><shadow type=\"math_number\"><field name=\"NUM\">0</field></shadow><block type=\"variables_get\"><field name=\"VAR\">index</field></block></value><value name=\"B\"><shadow type=\"math_number\"><field name=\"NUM\">3</field></shadow></value></block></value><statement name=\"DO0\"><block type=\"continue_keyword\"/></statement><next><block type=\"ScreenItem_Layout_add\"><value name=\"this\"><block type=\"variables_get\"><field name=\"VAR\">mainLayout</field></block></value><value name=\"item\"><block type=\"Control_createTextBlock\"><mutation xmlns=\"http://www.w3.org/1999/xhtml\" _expanded=\"1\" _input_init=\"true\"></mutation><value name=\"text\"><block type=\"text_join\"><mutation items=\"2\"/><value name=\"ADD0\"><shadow type=\"text\"><field name=\"TEXT\">The number is </field></shadow></value><value name=\"ADD1\"><shadow type=\"text\"><field name=\"TEXT\"/></shadow><block type=\"variables_get\"><field name=\"VAR\">index</field></block></value></block></value></block></value></block></next></block></statement></block></next></block></next></block></statement></block></xml>"}

輸出:

繼續 - 輸出

目録