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Handler 和 Message 是 Android 用來更新畫面的重要方法，有在開發 Android 的朋友都應該要知道這兩個的用法。而海芋最近使用這個方法來開發程式時，碰到了「android.util.AndroidRuntimeException: This message is already in use」這個問題，這是原本的寫法。 private int MSG_INCREASE_PROGRESSBAR = 9527; private int MSG_Done = 5566; private ProgressDialog m_progressDialog = null; private Runnable m_runnable = new Runnable(){ @Override public void run() { try { Message msg = new Message(); for (int i = 0; i < 100; i++){ msg.what = MSG_INCREASE_PROGRESSBAR; m_Handler.sendMessage(msg); } msg.what = MSG_Done; m_Handler.sendMessage(msg); } catch (Exception e) { e.printStackTrace(); } } }; private Handler m_Handler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what){ case MSG_INCREASE_PROGRESSBAR: if (m_progressDialog != null) m_progressDialog.incrementProgressBy(1); break; case MSG_DelteDone: if (m_progressDialog != null){ m_progressDialog.dismiss(); m_progressDialog = null; } } } }; 出現這個問題，海芋就去追查一下 Handler 這個 Class，原來在 Handler SendMessage 後，Handler 會將 Message 加入 MessageQueue 中，造成原本要處理的對象，已經不是原來的對象所致，所以要解決這個問題，必須在每次傳送 Message 給 Handler 前，先 New 一個 Message 元件，所以改成以下的寫法就可以囉！ private int MSG_INCREASE_PROGRESSBAR = 9527; private int MSG_Done = 5566; private ProgressDialog m_progressDialog = null; private Runnable m_runnable = new Runnable(){ @Override public void run() { try { for (int i = 0; i < 100; i++){ Message msg = new Message(); msg.what = MSG_INCREASE_PROGRESSBAR; m_Handler.sendMessage(msg); } Message msg = new Message(); msg.what = MSG_Done; m_Handler.sendMessage(msg); } catch (Exception e) { e.printStackTrace(); } } }; private Handler m_Handler = new Handler(){ @Override public void handleMessage(Message msg) { super.handleMessage(msg); switch (msg.what){ case MSG_INCREASE_PROGRESSBAR: if (m_progressDialog != null) m_progressDialog.incrementProgressBy(1); break; case MSG_DelteDone: if (m_progressDialog != null){ m_progressDialog.dismiss(); m_progressDialog = null; } break; } } };