總以為自己對Handler比較了解，但今天發現還是不了解，以后寫代碼得好好的看看android doc了，這樣才能理解的更深。
一直以為Handler.post(Runnable)為開啟一個線程，所以出現了一下問題。
我定義了一個Runnable用來實現短信的分段讀取：
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) { 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) { 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; } }
然后定義了一個Handler用來更新界面：
private class GetMmsHandler extends Handler{ @Override public void handleMessage(Message msg) {
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; } } }
但我發現每次都是等所有的短信讀取完畢后才會打印幾次handlerMessage 222222222222信息，所以界面更本沒有出現先顯示一些，然后陸續加載的過程，我就很奇怪，為什么會會是這樣呢，我在mGetMmsHandler.sendMessage后加了判斷，看這個消息是否發送成功，驗證后是發送成功了，我就查看Handler的doc，原來post(Runnable)是把這個Runnable加到當前的消息隊列中，所以等這個Runnable處理完畢后才會處理接受到的多次what為2的消息。
總結
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