zoukankan      html  css  js  c++  java
  • Speed up the display of Delphi list components

    If you use a Delphi component like a ListBox, Memo, TreeList, ListView,... and you add or modify a lot of items (lines, nodes,...), the component's performance becomes very slow. This is due to the fact that after each change, it is redrawn on the screen.

    Thus, modifying 10000 items of a ListBox causes 10000 redraws, and that takes from several seconds to several minutes, depending on the computer's speed and the complexity of the process. Imagine how slow it can become if the process involves inserting, deleting, modifying and swapping many thousands of items.

    But you can speed up things enormously with the following tip:

    Call BeginUpdate before making the changes to the items. When all changes are complete, call EndUpdate to show the changes on screen. BeginUpdate and EndUpdate prevent excessive redraws and speed up processing time when items are added, deleted, or inserted.

    Here's a simple source code example for using this technique with a ListBox:

      ListBox1.Items.BeginUpdate;
    for i := 1 to 10000 do
    ListBox1.Items.Add('abcd');
    ListBox1.Items.EndUpdate;

    To give you an idea of the improvement, we timed the code above (your PC may be faster or slower):
    »  without the BeginUpdate/EndUpdate lines: 4.3 seconds...
    »  with BeginUpdate/EndUpdate: 0.1 seconds, that's 43 times faster!

    Here's a source code example for using this technique with a Memo:

      Memo1.Lines.BeginUpdate;
    for i := 1 to 5000 do
    Memo1.Lines.Add('abcd');
    Memo1.Lines.EndUpdate;

    »  without BeginUpdate/EndUpdate: 25 seconds...
    »  with BeginUpdate/EndUpdate: 0.6 seconds!

  • 相关阅读:
    cocos2d-x项目101次相遇:在HelloWorld上--建立新场景
    MySQL优化之——日志
    Zoj2421 广搜
    GG链路过多port不足导致的报错OGG-01223
    java的InputStream和OutputStream的理解【转】
    JAVA编程规则
    JAVA的String 类
    JAVA的StringBuffer类
    android自带的处理Bitmap out Memory 的处理,我仅仅是改变了些写法成为自己用的东西
    NS3网络仿真(2):first.py
  • 原文地址:https://www.cnblogs.com/yunhaisoft/p/1452032.html
Copyright © 2011-2022 走看看