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Andrid prgramming curse Data strage Sessin bjectives Internal Strage Intrductin By Võ Văn Hải Faculty f Infrmatin Technlgies Andrid prvides several ptins fr yu t save persistent applicatin data.

Andrid prvides a way fr yu t expse even yur private data t ther applicatins with a cntent prvider.

1 Andrid prgramming curse Data strage Sessin bjectives Internal Strage Intrductin By Võ Văn Hải Faculty f Infrmatin Technlgies Andrid prvides several ptins fr yu t save persistent applicatin data. The slutin yu chse depends n yur specific needs, such as whether the data shuld be private t yur applicatin r accessible t ther applicatins (and the user) and hw much space yur data requires. Andrid prvides a way fr yu t expse even yur private data t ther applicatins with a cntent prvider. A cntent prvider is an ptinal cmpnent that expses read/write access t yur applicatin data, subject t whatever restrictins yu want t impse. 3 External Strage Databases Netwrk Cnnectin Strage Optins Stre private primitive data in key-value pairs. Internal Strage Stre private data n the device memry. External Strage Stre public data n the shared external strage. Databases Stre structured data in a private database. Netwrk Cnnectin Stre data n the web with yur wn netwrk server

$(%AndridSDKFlder%\tls\mrnitr.$ bat) The SharedPreferences class prvides a general framewrk that allws yu t save and retrieve persistent

Yu can use SharedPreferences t save any primitive data: bleans, flats, ints, lngs, and strings.

cm/ 5 7 Create T get a SharedPreferences bject fr yur applicatin, use ne f tw methds: getsharedpreferences()

2 Data strage mnitr Tl T mnitr data in emulatr, yu can use the tl Andrid Device Manager included in Andrid SDK (%AndridSDKFlder%\tls\mrnitr.bat) The SharedPreferences class prvides a general framewrk that allws yu t save and retrieve persistent key-value pairs f primitive data types. Yu can use SharedPreferences t save any primitive data: bleans, flats, ints, lngs, and strings. This data will persist acrss user sessins (even if yur applicatin is killed) Create T get a SharedPreferences bject fr yur applicatin, use ne f tw methds: getsharedpreferences() - Use this if yu need multiple preferences files identified by name, which yu specify with the first parameter. getpreferences() - Use this if yu need nly ne preferences file fr yur Activity. Because this will be the nly preferences file fr yur Activity, yu dn't supply a name

Get/Put values T write values: Call edit() t get a SharedPreferences.Editr.

Cmmit the new values with cmmit() T read values: Use SharedPreferences methds getxxx() - XXX is data type.

cm/ 9 11 Example Save & Restring instance states T save Activity instance variables, Andrid ffers a specialized

3 Get/Put values T write values: Call edit() t get a SharedPreferences.Editr. Add values with methds putxxx() XXX is data type. such as putblean() and putstring(). Cmmit the new values with cmmit() T read values: Use SharedPreferences methds getxxx() - XXX is data type. such as getblean() and getstring(). Example Example Save & Restring instance states T save Activity instance variables, Andrid ffers a specialized variatin f. By verriding an Activity s nsaveinstancestate event handler, yu can use its Bundle parameter t save UI instance values. Stre values using the same get and put methds as shwn fr, befre passing the mdified Bundle int the superclass s handler

Save & Restring instance states example Andrid's Preference APIs Preferences Andrid's Preference APIs Preferences Every setting fr yur app is represented by a specific subclass f the Preference class.

4 Save & Restring instance states example Andrid's Preference APIs Preferences Andrid's Preference APIs Preferences Every setting fr yur app is represented by a specific subclass f the Preference class. Each subclass includes a set f cre prperties that allw yu t specify things such as a title fr the setting and the default value. A few f the mst cmmn preferences are: CheckBxPreference Shws an item with a checkbx fr a setting that is either enabled r disabled. The saved value is a blean (true if it's checked). ListPreference Opens a dialg with a list f radi buttns. The saved value can be any ne f the supprted value types (listed abve). EditTextPreference Opens a dialg with an EditText widget. The saved value is a String Applicatins ften include settings that allw users t mdify app features and behavirs. Fr example, sme apps allw users t specify whether ntificatins are enabled r specify hw ften the applicatin syncs data with the clud. If yu want t prvide settings fr yur app, yu shuld use Andrid's Preference APIs t build an interface that's cnsistent with the user experience in ther Andrid apps (including the system settings) Andrid's Preference APIs Defining Preferences in XML 16 4

Preference APIs Using Preference Fragments Display

5 Andrid's Preference APIs Defining Preferences in XML Andrid's Preference APIs Creating Activity Andrid's Preference APIs Using Preference Fragments Display AndridManifest.xml Using the Internal Strage

Internal Strage Yu can save files directly n the device's internal strage. By default, files saved t the internal strage are private t yur applicatin and ther applicatins cannt access them.

Yu can pen it with penrawresurce(), passing the R.raw.<filename> resurce ID.

6 Internal Strage Yu can save files directly n the device's internal strage. By default, files saved t the internal strage are private t yur applicatin and ther applicatins cannt access them. When the user uninstalls yur applicatin, these files are remved. If yu want t save a static file in yur applicatin at cmpile time, save the file in yur prject res/raw/ directry. Yu can pen it with penrawresurce(), passing the R.raw.<filename> resurce ID. This methd returns an InputStream that yu can use t read the file (but yu cannt write t the riginal file) Internal Strage Steps T create and write a private file t the internal strage: 1. Call penfileoutput() methd with the name f the file and the perating mde. 2. Write t the file with write() methd. 3. Clse the stream with clse() methd. T read a file frm internal strage: 1. Call penfileinput() methd and pass it the name f the file t read. 2. Read bytes frm the file with read() methd. 3. Then clse the stream with clse() methd Internal Strage Static file Internal Strage Example

Internal Strage Saving cache files If yu'd like t cache sme data, rather than stre it persistently, yu shuld use getcachedir() methd t pen a File that represents the internal directry where yur

cm/ 25 27 Internal Strage Other useful methds getfilesdir() Gets the abslute path t the filesystem directry where yur internal files are saved.

7 Internal Strage Saving cache files If yu'd like t cache sme data, rather than stre it persistently, yu shuld use getcachedir() methd t pen a File that represents the internal directry where yur applicatin shuld save temprary cache files. When the device is lw n internal strage space, Andrid may delete these cache files t recver space. Using the External Strage Internal Strage Other useful methds getfilesdir() Gets the abslute path t the filesystem directry where yur internal files are saved. getdir() Creates (r pens an existing) directry within yur internal strage space. deletefile() Deletes a file saved n the internal strage. filelist() Returns an array f files currently saved by yur applicatin. External Strage Every Andrid-cmpatible device supprts a shared "external strage" that yu can use t save files. This can be a remvable strage media (such as an SD card) r an internal (nn-remvable) strage. Files saved t the external strage are wrld-readable and can be mdified by the user when they enable USB mass strage t transfer files n a cmputer. In rder t read r write files n the external strage, yur app must acquire the READ_EXTERNAL_STORAGE r WRITE_EXTERNAL_STORAGE system permissins. AndridManifest.xml

External Strage Checking media availability External Strage Example Befre yu d any wrk with

zer-cnfiguratin, transactinal SQL database engine supprts all the relatinal database features.

8 External Strage Checking media availability External Strage Example Befre yu d any wrk with the external strage, yu shuld always call the getexternalstragestate() methd t check whether the media is available. The media might be munted t a cmputer, missing, read-nly, r in sme ther state. Using Database intrductin is an in-prcess library that implements a selfcntained, server-less, zer-cnfiguratin, transactinal SQL database engine supprts all the relatinal database features. In rder t access this database, yu dn't need t establish any kind f cnnectins fr it like JDBC,ODBC e.t.c is a database that stres data t a file n a device. Andrid cmes in with built in database implementatin. Hme page:

Create a Database Using a SQL Helper Create a Database Using a SQL Helper Just like files that yu save n the device's internal strage, Andrid stres yur

When yu use this class t btain references t yur database, the system perfrms the ptentially lng-running peratins f creating and updating the database nly

T access yur database, instantiate yur subclass f OpenHelper: http://vvanhai.wrdpress.cm/ 33 35 Create a Database using methd database=database.

Sets the lcale f the database t the the system's current lcale. Call setlcale if yu wuld like smething else.

9 Create a Database Using a SQL Helper Create a Database Using a SQL Helper Just like files that yu save n the device's internal strage, Andrid stres yur database in private disk space that's assciated applicatin. Yur data is secure, because by default this area is nt accessible t ther applicatins. When yu use this class t btain references t yur database, the system perfrms the ptentially lng-running peratins f creating and updating the database nly when needed and nt during app startup. All yu need t d is call getwritabledatabase() r getreadabledatabase(). T access yur database, instantiate yur subclass f OpenHelper: Create a Database using methd database=database.pendatabase(path, factry, flags) Open the database accrding t the flags OPEN_READWRITE OPEN_READONLY CREATE_IF_NECESSARY and/r NO_LOCALIZED_COLLATORS. Sets the lcale f the database t the the system's current lcale. Call setlcale if yu wuld like smething else. Parameters: path: t database file t pen and/r create factry: an ptinal factry class that is called t instantiate a cursr when query is called, r null fr default flags: t cntrl database access mde Returns:the newly pened database Thrws:Exceptin - if the database cannt be pened

Create a Database using methd Put Infrmatin int a Database nt recmmendatin Read Infrmatin frm a Database http://vvanhai.wrdpress.cm/ 37 39 The first argument fr insert() is simply the table name.

10 Create a Database using methd Put Infrmatin int a Database nt recmmendatin Read Infrmatin frm a Database The first argument fr insert() is simply the table name. The secnd argument prvides the name f a clumn in which the framewrk can insert NULL in the event that the CntentValues is empty (if yu instead set this t "null", then the framewrk will nt insert a rw when there are n values). Return: the rw ID f the newly inserted rw, r -1 if an errr ccurred Read Infrmatin frm a Database

11 Delete Infrmatin frm a Database Update a Data T delete rws frm a table, yu need t prvide selectin criteria that identify the rws. Netwrk Cnnectin View in later sessin

CS5530 Mobile/Wireless Systems Using Google Map in Android

CS5530 Mobile/Wireless Systems Using Google Map in Android Mbile/Wireless Systems Using Ggle Map in Andrid Yanyan Zhuang Department f Cmputer Science http://www.cs.uccs.edu/~yzhuang UC. Clrad Springs Setup Install the Ggle Play services SDK Tls > Andrid > SDK