Parsing data in JSON form on Android

Last Update:2015-05-31 Source: Internet

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1, JSON (JavaScript Object Notation) definition:A lightweight data interchange format with good readability and easy-to-write features. The Industry's mainstream technology provides a complete solution (somewhat like regular expressions, which is supported in most languages today), enabling data exchange between different platforms. JSON uses a high-compatibility text format, and also has a similar behavior to the C language System.2, the structure of json:(1) name/value Pairs (unordered): similar to the familiar keyed list, Hash table, disctionary, and associative array. There is another class "Bundle" in the Android platform that has similar behavior in some way.(2) Array (ordered): A set of ordered data lists, processing This class is step-by, see in detail the implementation in Jsonparser.java.JSON objectThe Name/value object is an unordered collection of Pairs. {name:value, name:value, name:value ...}, example: {"name": "jack", "age": 20}JSON Arrays (array)An array is an ordered collection of values (value). [value, value, Value ...] The value (value) can be a string enclosed in double quotation marks (string), A numeric value (number), true, false, null, an object, or an array. These structures can be nested. A string is a collection of any number of Unicode characters surrounded by double quotation marks, escaped with a backslash . A character (character) is a separate string (character string).At the time of the test, the following string is Shown:<pre><pre>String result = "{\" name\ ": \" jack\ ", \" age\ ": 20}";</pre></pre>Example 1: array contains objects (object)[{"id": 1, "name": "jack", "age": $}, {"id": 2, "name": "tom", "age": 23}, ...]Example 2: the same object can contain an array(1) An object contains 1 arrays, 2 sub-objects{"root": [{"id": "001", "name": "jack"},{"id": "002", "name": "tom"},{"id": "003", "name": "helen"}], "total": 3, "success": true }(2) you can also object nested child objects, sub-objects nested arrays{"calendar": {"calendarlist": [ {"id": "001", "name": "jack"}, {"id": "002", "name": "tom"} ] } }Summary sentence: The format is varied and can be nested with each other .--------------------------------------------------------------------------------------------Contains four json-related classes and a exceptions in android:jsonarray, jsonobject, jsonstringer, jsontokener, jsonexception, In addition to the first two, the other in the analysis is not long use.(1) jsonobject:This is the basic unit in the system for JSON definition, which contains a pair of Key/value Values.Its response to the external (External: apply the ToString () method output Value) is reflected as a standard string (for example: {"JSON": "Hello, world"}, enclosing the outer brace with the key and value separated by the colon ":"). Its action format for internal (Internal) behavior is slightly, for example: initializing a jsonobject instance, referencing the internal put () method to add a value : New Jsonobject (). put ("JSON", "Hello, world" ! "), separated by a comma", "between key and value . The types of value include: Boolean, jsonarray, jsonobject, number, string, or the default value Jsonobject.null Object.There are two different methods of fetching values:Get (): used when determining the existence of a value, or a exception message will be thrown when the relevant key cannot be retrieved. Opt (): This method is relatively flexible and returns a default value when the specified value cannot be obtained, and does not throw an Exception. (2) jsonarray:It represents an ordered set of Values. Converting it to a string output (toString) is performed in the form of a square bracket, separated by a comma "," (for example: [value1,value2,value3], You can personally use the short code to understand its format more intuitively). The inside of this class also has query behavior, both get () and opt () can return the specified value through the index index, and the put () method is used to add or replace Values.similarly, The value type of this class can include: Boolean, jsonarray, jsonobject, number, string, or default value Jsonobject.null Object.(3) Jsonstringer:According to the official explanation, this class can help create jsontext quickly and easily. Its greatest advantage is that it can reduce program exceptions due to format errors, which can automatically create JSON text in strict accordance with JSON syntax rules (syntaxrules). Each Jsonstringer entity can only create one JSON Text.Follow the example below to learn about other relevant information: The result is a standard set of JSON text:{"name": "pig"}, where The. object () and. EndObject () must be used together in order to add a boundary to the value according to the object Standard. similarly, there is a standard set of methods for arrays to generate Boundaries. array () and. Endarray ().(4) Jsontokener:This is the class for the system to parse the JSON source string for the Jsonobject and Jsonarray constructors, which can extract numeric information from the source String.Jsonexception: is the exception information thrown by the json.org class.Practiced hand simple parsing of several common types, first write a class, implement a static method to call Jsonparser.java:<pre> packageujs.jsonparser;Importjava.util.ArrayList;Importjava.util.HashMap;Importjava.util.List;Importjava.util.Map;Importorg.json.JSONArray;Importorg.json.JSONException;Importorg.json.JSONObject; public classJsonparser {/*** JSON array inline JSON object * *@paramstring *, Data form string result = * "[{\" id\ ": 1,\" name\ ": \" piglet \ ", \" age\ ": 2},{\" id\ ": 2,\" Nam e\ ": \" puppy \ ", \" age\ ": 3}]" *; * @return * @throwsException*/ public Staticlist<map<string, string>>getjsonarray (string String) {List<map<string, string>> list =Newarraylist<map<string, string>>(); Map<string, string> map =NULL; Jsonarray jsonarray; Try{jsonarray=NewJsonarray (string); for(inti = 0; I < Jsonarray.length (); i++) {jsonobject Item=Jsonarray.getjsonobject (i); intid = item.getint ("id"); String name= Item.getstring ("name"); String age= Item.getstring ("age"); Map=Newhashmap<string, string>(); Map.put ("id", ID + ""); Map.put ("name", name); Map.put ("age", age); List.add (map); } } Catch(jsonexception E) {//TODO auto-generated Catch blockE.printstacktrace (); } /*** Test Print information, You can delete*/ for(map<string, string>Map2:list) {String ID= Map2.get ("id"); String name= Map2.get ("name"); String age= Map2.get ("age"); System.out.println ("id:" + ID + "name:" + name + "age:" +age ); } returnlist; } /*** JSON object embedded JSON array (array inline JSON Object) * *@paramString * For example: string result = * "{\" total\ ": 2,\" success\ ": true,\" arraydata\ ": [{\" id\ ": 1,\ "name\": \ "piglet \"},{\ "id\": 2,\ "name\": \ "kitten \"}]} "*; * @return * @throwsException*/ public Staticlist<map<string, string>>getjsonobject (string String) {List<map<string, string>> list =Newarraylist<map<string, string>>(); Map<string, string> map =NULL; Jsonobject jsonobject; inttotal ; Try{jsonobject=NewJsonobject (string); total= Jsonobject.getint ("total"); Boolean Success= Jsonobject.getboolean ("success"); System.out.println ("total:" + all + "| Success: "+ success);//Test data, information has been obtainedJsonarray Jsonarray = Jsonobject.getjsonarray ("arraydata");//gets the array inside the object for(inti = 0; I < Jsonarray.length (); i++) {jsonobject Item=Jsonarray.getjsonobject (i); intid = item.getint ("id");//gets the value corresponding to the objectString name = item.getstring ("name"); Map=Newhashmap<string, string> ();//Store in MapMap.put ("id", ID + "" "); Map.put ("name", name); List.add (map); } } Catch(jsonexception E) {//TODO auto-generated Catch blockE.printstacktrace (); } /*** Test data, can be deleted*/ for(map<string, string>Map2:list) {String ID= Map2.get ("id"); String name= Map2.get ("name"); System.out.println ("id:" + ID + "| Name: "+name); } returnlist; } /** * * @paramString * String result = * "{\" name\ ": \" piglet \ ", \" age\ ": all, \" content\ ": {\" questionstotal \ ": 2,\" questions\ ": [{\" question\ ": \" What ' s your name?\ ", \" answer\ ": \" piggy \ "},{\" question\ ": \" What ' s your age\ ", \" ans Wer\ ": \" 23\ "}]}}" *; * @return * @throwsException*/ public Staticlist<map<string, string>>Getjson (string String) {List<map<string, string>> list =Newarraylist<map<string, string>>(); Map<string, string> map =NULL; Jsonobject jsonobject; Try{jsonobject=NewJsonobject (string); String name= Jsonobject.getstring ("name"); intAge = Jsonobject.getint ("age"); System.out.println ("name:" + name + "| Age: "+ age");//test DataJsonobject Contentobject = Jsonobject.getjsonobject ("content"); String Questionstotal= Contentobject.getstring ("questionstotal");//gets a value from the objectSystem.out.println ("questionstotal:" + questionstotal);//Jsonarray Contentarray = Contentobject.getjsonarray ("questions"); for(inti = 0; I < Contentarray.length (); i++) {jsonobject Item= Contentarray.getjsonobject (i);//get each objectString question = item.getstring ("question");//gets the value corresponding to the objectString answer = item.getstring ("answer"); Map=Newhashmap<string, string> ();//Store in MapMap.put ("question", question); Map.put ("answer", answer); List.add (map); } } Catch(jsonexception E) {//TODO auto-generated Catch blockE.printstacktrace (); } /*** Test data, can be deleted*/ for(map<string, string>Map2:list) {String question= Map2.get ("question"); String Answer= Map2.get ("answer"); System.out.println ("question:" + question + "| Answer: "+answer); } returnlist; }}</pre>Here is a simple call:<pre><pre>String result = "[{\" id\ ": 1,\" name\ ": \" piglet \ "," age\ ": 2},{\" id\ ": 2,\" name\ ": \" puppy \ ", \" age\ ": 3}]"; // String result = // "{\" total\ ": 2,\" success\ ": true,\" arraydata\ ": [{\" id\ ": 1,\" name\ ": \" piggy \ "},{\" id\ ": 2,\" name\ ": \" kitten \ "}]}"; // String result = // "{\" name\ ": \" piglet \ ", \" age\ ":, \" content\ ": {\" questionstotal\ ": 2,\" questions\ ": [{\" question\ ": \" What ' s your Name?\ ", \" answer\ ": \" piglet \ "},{\" question\ ": \" What ' s your age\ ", \" answer\ ": \" 23\ "}]}"; Jsonparser.getjsonarray (result);</pre></pre>Parsing data in JSON form on Android

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