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问题 I am getting a bit frustrated with an issue that I cannot seem to fully understand. I have a listview with items and when I click them I want to pass an object (Parcelable) to a new activity. This is the code below: lv_Entries.setOnItemClickListener(new AdapterView.OnItemClickListener() { public void onItemClick(AdapterView<?> parent, View view, int position, long id) { Intent getItchesScreen = new Intent(Home.this, Itches.class); getItchesScreen.putExtra("i", 3); Entry e = entries.get

问题 I came across this code: if (txtUPC.Text.ToString() != null) ...and wonder if this test is even valid - is it possible for the text property to be null? txtUPC is not a dynamically created control. It can be empty, of course, or contain just whitespace, but null? If so, I'd like to know how. Then again, call ToString() on the text property seems like wearing suspenders with a belt, too. UPDATE So it seems to me, that for me (remember: .NET 1.1, Windows CE/Compact Framework), this: if (txtUPC

问题 Let's say we have the following sql statement: INSERT INTO myTable VALUES (1,"test") In my python code the first value is either an integer or NULL. How can I insert NULL value using python code? Code snippet: var1 = getFirstValue() var2 = getSecondValue() qry = "INSERT INTO myTable VALUES (%d,%s)" % (var1,var2) Whenever var1 is None it is throwing error, but I want NULL to be inserted. 回答1: You can use: qry = "INSERT INTO myTable VALUES ({0}, {1})".format(var1, var2) 回答2: Since you marked

问题 I am using Google Protocol Buffer for message serialization. This is my sample proto file content. package MessageParam; message Sample { message WordRec { optional uint64 id = 1; optional string word = 2; optional double value = 3; } message WordSequence { repeated WordRec WordSeq = 1; } } I am trying to serialize the message in C++ like following MessageParam::Sample::WordSequence wordseq; for(int i =0;i<10;i++) { AddRecords(wordseq.add_wordseq()); } std::string str = wordseq

问题 I'm trying to place a button over a webview, and I found the easiest way to do it is through xml. My MainActivity onCreate looks as such: public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); Button buttonClick = (Button)findViewById(R.id.playButton); mWebview = (WebView)findViewById(R.id.webview); mWebview.getSettings().setJavaScriptEnabled(true); // enables javascript System.out.println("Loading Webpage..."); new tts().execute(""); mWebview.loadUrl("http:/

问题 I'm very new with javascript and trying to play around with Mail Merge function in Google spreadsheet and mail. I copied the tutorial script and made some necessary changes (at least what I can think of). But when I tried to run the script, I got TypeError: Cannot read property "length" from null. (line 43) The line 43 mentioned above is the for loop below. Can someone please help let me know what to be fixed so I can run the script? // Replaces markers in a template string with values define

问题 What are the advantages of having String a = null; if(null != a) over if(a !=null) I tried both statement and they worked fine. Any suggestions why should I go with the first one? 回答1: Both are the same, however if you are checking for == on a boolean value: if(a == true) vs if(true == a) The latter would be better due to the tendency of typographical error by typing only = instead of == : if(a = true) //still compilable but not what you intended if(true = a) //cannot be compiled, hence you

问题 This question already has answers here : Closed 8 years ago . Possible Duplicate: json_encode is returning NULL? I'm having a strange problem with json_encode() in php. Pretty simple code: $content = json_encode(array('content1' => $arm_length, 'content2' => $body_length)); echo $content; $arm_length and $body_length variables contain the HTML markup for two select dropdown menus. My problem is when it echo 's out it show's NULL for content1 and content2 . If I take the json_encode() away and

问题 I am doing a query with a trivial join, with the intention of finding the newest record that the user hasn't voted on yet: SELECT v.user_id, v.version_id, vv.user_id FROM versions v LEFT JOIN versions_votes vv ON v.version_id = vv.version_id WHERE vv.user_id != 39; Curiously, this returns no rows if vv.user_id is null. My admittedly pedestrian understanding of the problem is that NULL cannot be equal to anything - that's why we have to test for IS NULL rather than =NULL in the first place.

问题 Simple question: In php, is var set to null same as undefined? In addition, what is simplest way to check is var null? How to use this functionality without breaking code, eg. by setting something optional in config array that can be set to null . If check for null with is_null it can potentially break code if var is not defined. is_null is completely opposite of isset , but can used only and only if you are certain that var is defined. Fore every other cases looks that isset more appropriate