JavaMe如何实现自适应滚动显示

发布时间：2023-07-25 以下文章来源于网友投稿，内容仅供参考！

【原理】

JavaMe中有一个坐标变换的功能。当触发相应的按键事件时，我们就让其显示相应的页，并且使滚动条滚动到相应的位置。

【代码清单】

ShowHelp.java

package .token.view;   import javax.microedition.lcdui.Font;  import javax.microedition.lcdui.Graphics;  import javax.microedition.lcdui.game.GameCanvas;   import .token.util.StringDealMethod;  import .token.util.UIController;  import .token.viewponents.*;   public class ShowHelp  extends GameCanvas  {      private UIController controller;      private Graphics graphics;      private Font ft;      private int width;      private int height;            private Menu menu;      private Head head;      private BackGroud backGroud;            private int page = 0;      private int currentPageIndex = 0;      private int bodyHeight;      private int dir = 0;             public ShowHelp(UIController control)       {          super(false);          this.controller=control;          setFullScreenMode(true);                    width = getWidth();          height = getHeight();                    menu = new Menu(this);          head = new Head(this);          backGroud = new BackGroud(this);       }            public void show()      {          int margin = 0;          graphics = getGraphics();                    graphics.clipRect(0,0, width, height);          backGroud.drawBackGroud(this, graphics);            head.drawHead(this, graphics, "帮助");          menu.drawMenu(this, graphics, "","返回");          //flushGraphics();                    ft = Font.getFont(Font.FACE_PROPORTIONAL,Font.STYLE_BOLD,Font.SIZE_MEDIUM);                    String info = "1 滚动分页显示；\n"                 +"2 滚动分页显示；\n"                 +"3 滚动分页显示；\n"                 +"4 滚动分页显示；\n"                 +"5 滚动分页显示；\n"                 +"6 滚动分页显示；\n"                 +"7 滚动分页显示；\n"                 +"8 滚动分页显示；\n"                 +"9 滚动分页显示；\n"                 +"10 滚动分页显示；\n"                 +"11 滚动分页显示；\n"                 +"12 滚动分页显示；\n"                 +"13 滚动分页显示；\n"                 +"14 滚动分页显示；\n"                 +"15 滚动分页显示；\n"                 +"16 滚动分页显示；\n"                 +"17 滚动分页显示；\n"                 +"18 滚动分页显示；\n"                 +"19 滚动分页显示；\n"                 +"20 滚动分页显示；\n"                 +"21 滚动分页显示；\n"                 +"22 滚动分页显示；\n"                 +"23 滚动分页显示；\n"                 +"24 滚动分页显示；\n"                 +"25 滚动分页显示；\n"                 +"26 滚动分页显示；\n"                 +"27 滚动分页显示；\n"                 +"28 滚动分页显示；\n"                 +"29 滚动分页显示；\n"                 +"30 滚动分页显示；\n"                 +"31 滚动分页显示；\n"                 +"32 滚动分页显示；\n"                 +"33 滚动分页显示；\n"                 +"34 滚动分页显示；\n";                            String info_wrap1[] = StringDealMethod.format(info, width-15, ft);           page = info_wrap1.length*ft.getHeight()/(height-head.menuHeight-menu.menuHeight-2*margin)+1;          bodyHeight = ((int) (height-head.menuHeight-menu.menuHeight)/ft.getHeight())*ft.getHeight();          margin = (height-head.menuHeight-menu.menuHeight-bodyHeight)/2;                    graphics.setFont(ft);          graphics.setColor(Color.text);          graphics.clipRect(0, head.menuHeight+margin, width, bodyHeight);          graphics.translate(0, dir*currentPageIndex*bodyHeight);                    for(int i=0; i<info_wrap1.length;i++)          {              graphics.drawString(info_wrap1[i],5, i * ft.getHeight()+head.menuHeight+margin, Graphics.TOP|Graphics.LEFT);          }                    graphics.translate(0, -dir*currentPageIndex*bodyHeight);                    drawScrollBar();          flushGraphics();                    //System.out.println(graphics.getTranslateY());                }            private void drawScrollBar()      {          int barHeight = height-head.menuHeight-menu.menuHeight;                    graphics.setColor(Color.menuFrame);          graphics.fillRect(width-3, head.menuHeight, 2, barHeight);          graphics.setColor(Color.selectBg);          graphics.fillRect(width-4, head.menuHeight+(currentPageIndex)*barHeight/page, 4, barHeight/page);      }            protected void keyPressed(int keyCode)      {          //System.out.println(keycode);          switch(keyCode)          {              case KeyID.SOFT_RIGHT:              {                  String flag = "0";                  Object [] args = {flag,""};                  controller.handleEvent(UIController.EventID.EVENT_MAIN_SCREEN,args);                  break;              }              default:                      ;          }                    keyCode = getGameAction(keyCode);          //System.out.println(page);                    switch(keyCode)          {                            case UP:              {                  dir = -1;                                                      if(currentPageIndex>0)                  {                      currentPageIndex--;                  }                  else                   {                      //dir = 0;                  }                                    show();                  break;                                }              case DOWN:              {                  dir = -1;                  if(currentPageIndex<page-1)                  {                      currentPageIndex++;                  }                  else                   {                         //dir = 0;                  }                                    show();                  break;              }          }      }   }

【分析】

1 字符串拆分

String info_wrap1[] = StringDealMethod.format(info, width-15, ft);

2 避免字截断

如何在指定的区域内绘制整行文本，而不会因为字体或屏幕高度的改变使文本出现截断的问题，使文本出现“半截字”的问题呢？

bodyHeight = ((int) (height-head.menuHeight-menu.menuHeight)/ft.getHeight())*ft.getHeight();

经过上述处理后，滚动区域的高度bodyHeight总会是字体高度的整数倍，这样就不会出现上述字截断的问题了。

3 绘制文本

for(int i=0; i<info_wrap1.length;i++)  {      graphics.drawString(info_wrap1[i],5, i * ft.getHeight()+head.menuHeight+margin, Graphics.TOP|Graphics.LEFT);  }

4 坐标变换

graphics.clipRect(0, head.menuHeight+margin, width, bodyHeight);  graphics.translate(0, dir*currentPageIndex*bodyHeight);

文本绘制完成后，将坐标变换回来。

graphics.translate(0, -dir*currentPageIndex*bodyHeight);

5 绘制滚动条

private void drawScrollBar()  {      int barHeight = height-head.menuHeight-menu.menuHeight;            graphics.setColor(Color.menuFrame);      graphics.fillRect(width-3, head.menuHeight, 2, barHeight);      graphics.setColor(Color.selectBg);      graphics.fillRect(width-4, head.menuHeight+(currentPageIndex)*barHeight/page, 4, barHeight/page);  }

6 事件处理

当检测到按键事件后，进行翻页操作。

protected void keyPressed(int keyCode)  {      //System.out.println(keycode);      switch(keyCode)      {          case KeyID.SOFT_RIGHT:          {              String flag = "0";              Object [] args = {flag,""};              controller.handleEvent(UIController.EventID.EVENT_MAIN_SCREEN,args);              break;          }          default:              ;      }                keyCode = getGameAction(keyCode);      //System.out.println(page);                switch(keyCode)      {                    case UP:          {              dir = -1;                                                      if(currentPageIndex>0)              {                  currentPageIndex--;              }              else               {                  //dir = 0;              }                            show();              break;                        }          case DOWN:          {              dir = -1;              if(currentPageIndex<page-1)              {                  currentPageIndex++;              }              else               {                     //dir = 0;              }                                show();              break;          }      }  }