Android(安卓)Hander机制的理解

总以为自己对Handler比较了解，但今天发现还是不了解，以后写代码得好好的看看android doc了，这样才能理解的更深。
一直以为Handler.post(Runnable)为开启一个线程，所以出现了一下问题。
我定义了一个Runnable用来实现短信的分段读取：

private class SubSectionRunnable implements Runnable{          private Cursor mCursor;          private final int RECIPIENT_IDS = 3;          private final int SNIPPET = 4;          private String mRecipient;          private String mSnippet;          private String mNumber;          private Long mSnippetCS;          private String mName;          private String mThreadId;          private final int mFirstQueryStep = 20;          private final int mOtherQueryStep = 80;          private Long mDate = 0l;          private boolean mIsFirstQuery = true;          private TestSpeed mTestSpeed1 = new TestSpeed();          private TestSpeed mTestSpeed2 = new TestSpeed();          @Override          public void run() {              mTestSpeed1.loadBeginTime();              mCursor = getContentResolver().query(THREADS_URI,                      ALL_THREADS_PROJECTION, null, null, "date DESC limit " + mFirstQueryStep);              while(mCursor != null && mCursor.getCount() > 0){                  Log.i("xiao", "onPostExecute new " + mCursor.getCount());                  ConversationInfo conver = new ConversationInfo();                  mConversationInfoPreviousList.add(conver);                  while(mCursor.moveToNext()){                      mThreadId = mCursor.getString(ID);                      mDate = mCursor.getLong(DATE);                      mRecipient = mCursor.getString(RECIPIENT_IDS);                      mSnippetCS = mCursor.getLong(SNIPPET_CS);                      if(mSnippetCS ==0){                          mSnippet = mCursor.getString(SNIPPET);                      }                      else{                          try {                              mSnippet = new String(                                      mCursor.getString(SNIPPET).getBytes("ISO8859_1"), "utf-8");                          } catch (UnsupportedEncodingException e) {                              // TODO Auto-generated catch block                              e.printStackTrace();                          }                      }                      Cursor cr = getContentResolver().query(                              Uri.parse("content://mms-sms/canonical-addresses"),                              new String[] { "_id", "address" }, "_id=?",                              new String[] { mRecipient }, null);                      if(cr != null && cr.moveToFirst()){                          mNumber = cr.getString(1);                          mName = getContactNameByPhone(cr.getString(1));                      }                      else{                          mNumber = "";                          mName = null;                      }                      ConversationInfo conversation = new ConversationInfo(mRecipient, mSnippet, mNumber, mSnippetCS, mName, mThreadId);                      mConversationInfoPreviousList.add(conversation);                  }                  for( int i = 0; i < mConversationInfoPreviousList.size(); i++){                      try {                          mConversationInfoAdapterList.add(mConversationInfoPreviousList.get(i).clone());                      } catch (CloneNotSupportedException e) {                          // TODO Auto-generated catch block                          e.printStackTrace();                      }                  }                  mCursor.close();                  if(mIsFirstQuery){                      Message message = new Message();                      message.what = 1;                      boolean flag1 = mGetMmsHandler.sendMessage(message);                      Log.i("xiao", "flag1 = " + flag1);                      mIsFirstQuery = !mIsFirstQuery;                      mTestSpeed1.loadEndTime();                      mTestSpeed1.printDuration();                  }                  Message message = new Message();                  message.what = 2;                  boolean flag2 = mGetMmsHandler.sendMessage(message);                  Log.i("xiao", "flag2 = " + flag2);                  mTestSpeed2.loadEndTime();                  mTestSpeed2.printDuration();                  mCursor = null;                  mTestSpeed2.loadBeginTime();                  mCursor = getContentResolver().query(THREADS_URI,                          ALL_THREADS_PROJECTION, "date < " + mDate, null, "date DESC limit " + mOtherQueryStep);                  }          }          public String getContactNameByPhone(String number) {              String name = "";              Uri personUri = Uri.withAppendedPath(                      ContactsContract.PhoneLookup.CONTENT_FILTER_URI, number);              try{                  Cursor cur = getContentResolver().query(personUri,                      new String[] { PhoneLookup.DISPLAY_NAME },                      null, null, null );              if(cur != null){                  if( cur.moveToFirst() ) {                      int nameIdx = cur.getColumnIndex(PhoneLookup.DISPLAY_NAME);                      name = cur.getString(nameIdx);                  }                  cur.close();              }              }              catch(Exception e){                  Log.i("xiao", "" + e.getMessage());              }              return name;          }      }

然后定义了一个Handler用来更新界面：

private class GetMmsHandler extends Handler{          @Override          public void handleMessage(Message msg) {              // TODO Auto-generated method stub              super.handleMessage(msg);              int what = msg.what;              switch(what){              case 0:                  showProgress();                  mGetMmsThread.start();                  break;              case 1:                  hideProgress();                  break;              case 2:                  Log.i("xiao", "handleMessage 22222222222222");                  mConversationAdapter.notifyDataSetChanged();                  break;              }          }      }

但我发现每次都是等所有的短信读取完毕后才会打印几次handlerMessage 222222222222信息，所以界面更本没有出现先显示一些，然后陆续加载的过程，我就很奇怪，为什么会会是这样呢，我在mGetMmsHandler.sendMessage后加了判断，看这个消息是否发送成功，验证后是发送成功了，我就查看Handler的doc，原来post(Runnable)是把这个Runnable加到当前的消息队列中，所以等这个Runnable处理完毕后才会处理接受到的多次what为2的消息。

更多相关文章

随机推荐