MIDP终端模拟之一：一个简单的模拟器MIDlet

您应该记住一个细节：在测试它是设备上的 up 还是 down 按钮之前，您必须将键代码转换为游戏代码。某些设备上映射到 up 或 down 概念的键不只一个，有些有滚轴或其他专用的输入设备；使用 getGameAction() 能使该方法在所有情况下都能正确工作。keyRepeated() 也可做很多相同的工作，但是一次会移动滚动偏移量半个屏幕。

Telnet MIDlet

现在我们有了一个用于后端的前端，我们需要将他们与 MIDlet 结合成一体。Weather Underground 仍旧提供了一个免费的 telnet 服务，使用它编写一个 MIDlet 以检索最新的天气状况是一个有用的练习。而且，这个任务很有代表性，正是您希望用终端模拟 MIDlet 所做的那类事情：连接到远程服务器、登录和提取某类数据显示在屏幕上。

看一看 MIDTerm.java 的清单。它是一个极其标准的 MIDlet，从应用程序描述符中读取配置选项，然后设置显示和命令。在启动时，startApp() 调用 connect()，connect() 则生成调用 run() 的新线程：

public void run()
{
    String connectString = "socket://" + host + ':' + port;
    
    try
    {
        canvas.receive( toASCII( "Connecting...\n" ) );
        
        connection = new TelnetConnection( 
            (StreamConnection) Connector.open( 
                connectString, Connector.READ_WRITE, true ) );
        input = connection.openInputStream();
        output = connection.openOutputStream();
        
        // server interaction script
        try
        {
            // suppress content until first "continue:" 
            waitUntil( 
                input, new String[] { "ontinue:" }, false );
            output.write( toASCII( "\n" ) );
            output.flush();
            
            // show content until city code prompt
            waitUntil( 
                input, new String[] { "code--" }, true );
            output.write( toASCII( city + '\n' ) );
            canvas.receive( toASCII( city + '\n' ) ); 
            output.flush();
            
            // keep advancing pages until "Selection:" prompt
            while ( !"Selection:".equals( 
                waitUntil( input, new String[] { 
                    "X to exit:", "Selection:" }, true ) ) )
            {
                output.write( toASCII( "\n" ) );
                output.flush();
                canvas.receive( toASCII( "\n" ) );
            }
            // exit will cause disconnect
            output.write( toASCII( "X\n" ) );
            output.flush();
            canvas.receive( toASCII( "X\n" ) );
            
            // keep reading until "Done" or disconnected
            waitUntil( input, new String[] { "Done" }, true );
        }
        catch ( IOException ioe )
        {
            System.err.println( 
                "Error while communicating: " 
                + ioe.toString() );
            canvas.receive( toASCII( "\nLost connection." ) );
        }
        catch ( Throwable t )
        {
            System.err.println( 
                "Unexpected error while communicating: " 
                + t.toString() );
            canvas.receive( toASCII( 
                "\nUnexpected error: " + t.toString() ) );
        }
    }
    catch ( IllegalArgumentException iae )
    {
        System.err.println( "Invalid host: " + host );
        canvas.receive( toASCII( "Invalid host: " + host ) );
    }        
    catch ( ConnectionNotFoundException cnfe )
    {
        System.err.println( 
            "Connection not found: " + connectString );
        canvas.receive( toASCII( 
            "Connection not found: " + connectString ) );
    }        
    catch ( IOException ioe )
    {
        System.err.println( 
            "Error on connect: " + ioe.toString() );
        canvas.receive( toASCII( 
            "Error on connect: " + ioe.toString() ) );
    }        
    catch ( Throwable t )
    {
        System.err.println( 
            "Unexpected error on connect: " + t.toString() );
        canvas.receive( toASCII( 
            "Unexpected error on connect: " + t.toString() ) );
    }        
    
    // clean up
    disconnect();
    canvas.receive( toASCII( "\nDisconnected.\n" ) );
}