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J2ME中利用MMAPI播放聲音

編輯：J2ME

了解J2ME可選包MMAPI一文向讀者介紹了MMAPI的基本知識，掌握MMAPI的靈活性應該是重點。本文將講述如何在實際開發中使用MMAPI。

本文的目的是為讀者提供處理不同情況的代碼，您可以參考MMAPI DOC。

播放單音
try {
Manager.playTone(ToneControl.C4, 5000 /* millisec */, 100 /* max vol */);
} catch (MediaException e) { }
簡單媒體重放功能實現
try {
    Player p = Manager.createPlayer("http://webserver/music.mp3");
    p.setLoopCount(5);
    p.start();
} catch (IOException ioe) {
} catch (MediaException me) { }
詳細重放控制
static final long SECS_TO_MICROSECS = 1000000L;
Player p;
VolumeControl vc;
try {
    p = Manager.createPlayer("http://webserver/music.mp3");
    p.realize();
   // Set a listener.
   p.addPlayerListener(new Listener());
   // Grab volume control for the player.
   // Set Volume to max.
   vc = (VolumeControl)p.getControl("VolumeControl");
   if (vc != null)
      vc.setLevel(100);
   // Set a start time.
   p.setMediaTime(5 * SECS_TO_MICROSECS);
   // Guarantee that the player can start with the smallest latency.
   p.prefetch();
   // Non-blocking start
   p.start();
} catch (IOException ioe) {
} catch (MediaException me) { }
class Listener implements PlayerListener {
    public void playerUpdate(Player p, String event, Object eventData) {
        if (event == END_OF_MEDIA || event == STOP_AT_TIME) {
            System.out.println("Done processing");
            try {
                p.setMediaTime(5 * SECS_TO_MICROSECS);
                p.start();
            } catch (MediaException me) { }
            break;
        }
    }
}

實現MIDI重放控制

Player p;
TempoControl tc;
try {    
p = Manager.createPlayer("http://webserver/tune.mid");    
p.realize();    // Grab the tempo control.    
tc = (TempoControl)p.getControl("TempoControl");    
tc.setTempo(120000); // 120 beats/min    
p.start();
} catch (IOException ioe) {
} catch (MediaException me) { 
}

視頻重放功能實現

Player p;
VideoControl vc;
try {    
p = Manager.createPlayer("http://webserver/movIE.mpg");    
p.realize();    // Grab the video control and set it to the current display.    
vc = (VideoControl)p.getControl("VideoControl");    
if (vc != null) {        
Form form = new Form("video");        
form.append((Item)vc.initDisplayMode(vc.USE_GUI_PRIMITIVE, null));        
Display.getDisplay(midlet).setCurrent(form);    
}   
 p.start();
} catch (IOException ioe) {
} catch (MediaException me) { 
}

播放RMS內存儲的數據

RecordStore rs;
int recordID;   :  // code to set up the record store.
try {    
InputStream is = new    ByteArrayInputStream(rs.getRecord(recordID));    
Player p = Manager.createPlayer(is, "audio/X-wav");    
p.start();
} catch (IOException ioe) {
} catch (MediaException me) { 
}

播放Jar文件中存儲的媒體

/** Notice that in MIDP 2.0, the wav format is mandatory only *//** in the case that the device supports sampled audio.       */
try {    
InputStream is = getClass().getResourceAsStream("audio.wav");   
Player p = Manager.createPlayer(is, "audio/X-wav");    
p.start();
} catch (IOException ioe) {
} catch (MediaException me) { 
}

不同Player的同步

Player p1, p2;
try {    
p1 = Manager.createPlayer("http://webserver/tune.mid");    
p1.realize();    
p2 = Manager.createPlayer("http://webserver/movIE.mpg");    
p2.realize();    
p2.setTimeBase(p1.getTimeBase());    
p1.prefetch();    
p2.prefetch();    
p1.start();    
p2.start();
} catch (IOException ioe) {
} catch (MediaException me) { 
}

產生單音序列
byte tempo = 30; // set tempo to 120 bpm
byte d = 8;      // eighth-note

byte C4 = ToneControl.C4;;
byte D4 = (byte)(C4 + 2); // a whole step
byte E4 = (byte)(C4 + 4); // a major third
byte G4 = (byte)(C4 + 7); // a fifth
byte rest = ToneControl.SILENCE; // rest

byte[] mySequence = {
    ToneControl.VERSION, 1,   // version 1
    ToneControl.TEMPO, tempo, // set tempo
    ToneControl.BLOCK_START, 0,   // start define "A" section
    E4,d, D4,d, C4,d, E4,d,       // content of "A" section
    E4,d, E4,d, E4,d, rest,d,
    ToneControl.BLOCK_END, 0,     // end define "A" section
    ToneControl.PLAY_BLOCK, 0,    // play "A" section
    D4,d, D4,d, D4,d, rest,d,     // play "B" section
    E4,d, G4,d, G4,d, rest,d,
    ToneControl.PLAY_BLOCK, 0,    // repeat "A" section
    D4,d, D4,d, E4,d, D4,d, C4,d // play "C" section
};

try{
    Player p = Manager.createPlayer(Manager.TONE_DEVICE_LOCATOR);
    p.realize();
    ToneControl c = (ToneControl)p.getControl("ToneControl");
    c.setSequence(mySequence);
    p.start();
} catch (IOException ioe) {
} catch (MediaException me) { }

語音捕獲和錄音功能的實現

try {    // Create a DataSource that captures live audio.    
Player p = Manager.createPlayer("capture://audio");    
p.realize();    // Get the RecordControl, set the record location, and     
// start the Player and record for 5 seconds.    
RecordControl rc = (RecordControl)p.getControl("RecordControl");    
rc.setRecordLocation("file:/tmp/audio.wav");    
rc.startRecord();    
p.start();    
Thread.currentThread().sleep(5000);    
p.stop();    
rc.stopRecord();    
rc.commit();
} catch (IOException ioe) {
} catch (MediaException me) {
} catch (InterruptedException e) { 
}

實現攝像功能
Player p;
VideoControl vc;// initialize camera 
try {    
p = Manager.createPlayer("capture://video");    
p.realize();    // Grab the video control and set it to the current display.    
vc = (VideoControl)p.getControl("VideoControl");    
if (vc != null) {        
Form form = new Form("video");        
form.append((Item)vc.initDisplayMode(vc.USE_GUI_PRIMITIVE, null));        
Display.getDisplay(midlet).setCurrent(form);    
}    
p.start();
} catch (IOException ioe) {
} catch (MediaException me) { 
}// now take a picturetry {    byte[] pngImage = vc.getSnapshot(null);    
// do something with the image ...}
 catch (MediaException me) { }


在後面的文章中我們將通過完整的實例演示如何使用MMAPI開發應用程序。