Lập trình android C10 luutrutruyxuatdulieutrongungdung

Ch ng 10 L U TR VÀ TRUY XU T D LI U TRONG NG D NG Lê V n H nh levanhanhvn@gmail.com N I DUNG 1.Shared Preferences B l u tr B l u tr SQLite Databases Content Provider SharedPreferences • L u tr d li u d ng c b n • Ch h tr m t s ki u d li u c b n: booleans, float, int, long, string • Ho t đ ng theo ki u l u tr c ng nh truy xu t thông qua c p giá tr key/value • Các d li u đ c l u tr truy xu t qua t ng phiên (session) t ng tác c a ng d ng v i ng i dùng • S d ng đ i t ph ng th c: ng l p SharedPreference thơng qua GetsharedPreferences(string, int) SharedPreferences • T ođ it ng SharedPreferences: SharedPreferences sharedPre = getSharedPreferences(PREFS_NAME, mode); Trong đó: o PREFS_NAME: tên c a sharedPreference c n t o o Mode: ki u ghi d li u     MODE_PRIVATE: mode ghi m c đ nh, ch có nh t ng d ng t o t p tin đ c phép truy c p vào MODE_WORLD_READABLE: cho phép ng d ng khác truy c p vào MODE_WORLD_WRITEABLE: cho phép ng d ng khác truy c p s a đ i MODE_MULTI_PROCESS: cho phép nhi u ti n trình ng d ng truy xu t vào m t th i m SharedPreferences • B sung thơng tin cho đ i t thông qua đ i t ng Editor ng SharedPreferences(): Ví d : SharedPreferences.Editor editor = sharedPre.edit(); editor.putBoolean(“isTrue”, true); editor.putFloat(“lastFloat”, 1f); editor.putInt(“wholeNumber”, 2); editor.putLong(“aNumber”, 3l); editor.putString(“textEntryValue”, “Not Empty”); //L u SharedPreference editor.commit(); SharedPreferences • L y d li u SharedPreferences(): s d ng hàm get tùy theo t ng lo i d li u Ví d : boolean isTrue = sharedPre.getBoolean(“isTrue”, false); float lastFloat = sharedPre.getFloat(“lastFloat”, 0f); int wholeNumber = sharedPre.getInt(“wholeNumber”, 1); long aNumber = sharedPre.getLong(“aNumber”, 0); String stringPreference= sharedPre.getString(“textEntryValue”, “”); B L U TR TRONG • L u d li u riêng b nh thi t b • Khi ng d ng đ c cài đ t, h th ng cung c p vùng b nh dành cho vi c l u tr d li u cho m i ng d ng riêng • Khi ng i dùng g b ng d ng, vùng b nh s đ c xóa • T o l u tr file vào b l u tr o o o • G i openFileOutput() v i tên file ch đ truy c p file Ghi lên file s d ng ph ng th c write() óng stream v i ph ng th c close() c file t b l u tr o o o G i openFileInput() v i tên file c n đ c c n i d ng t file s d ng ph ng th c read() óng stream v i ph ng th c close() B L U TR TRONG • Ví d 1: String FILENAME = "hello_file"; String string = "hello world!"; FileOutputStream fos = openFileOutput(FILENAME, Context.MODE_PRIVATE); fos.write(string.getBytes()); fos.close(); B L U TR NGỒI • L u tr d li u public b nh ngồi • M i thi t b Android có th h tr b l u tr ngồi s d ng l u file (nh SDcard) • D li u đ c l u tr b l u tr ngồi có th đ c thay đ i b i ng i dùng, có th đ ng b v i máy tính cá nhân • Tr c làm vi c v i b l u tr c n ki m tra tr ng thái c a b l u tr B L U TR NGỒI • Ví d : boolean mExternalStorageAvailable = false; boolean mExternalStorageWriteable = false; String state = Environment.getExternalStorageState(); if (Environment.MEDIA_MOUNTED.equals(state)) { // We can read and write the media mExternalStorageAvailable=mExternalStorageWriteable= true; } else if (Environment.MEDIA_MOUNTED_READ_ONLY.equals(state)) { // We can only read the media mExternalStorageAvailable = true; mExternalStorageWriteable = false; } else { /* Something else is wrong It may be one of many other states, but all we need to know is we can neither read nor write*/ mExternalStorageAvailable=mExternalStorageWriteable=false; } CONTENT PROVIDER • Là n i đóng gói d li u cho phép thành ph n ng d ng ho c ng d ng khác truy c p s d ng • Android cung c p m t s gói content provider dùng cho vi c l u tr chung: • Browser • CallLog • Contact (people, phones, photos, group) • MediaStore (music, video, image) • Setting CONTENT PROVIDER • Mơ hình d li u theo đ nh d ng c t dòng gi ng nh c s d li u V i m i c t tr ng d li u m i dòng m t record • Cách th c ho t đ ng gi ng giao th c REST web • S d ng chu i URI đ th c hi n vi c rút trích c ng nh l u d li u content provider Ví d : content://com.android.book.BookProvider content://com.android.book.BookProvider/7 • C n khai báo file AndroidManifest.xml cho bi t ng d ng s d ng nh ng content provider CONTENT PROVIDER • S d ng Cursor đ th c hi n thao b ng d li u c a provider Cursor • M t s ph d li u: ng th c đ u n Cursor thao tác movetoFisrt movetoPrevious movetoNext movetoPosition getCount getColumnName getPosititon getColumnIndexOrThrow getColumnNames CONTENT PROVIDER • Ví d : if (cur.moveToFirst()==false) { // no rows empty cursor return; } //The cursor is already pointing to the first row //lets access a few columns int nameColumnIndex = cur.getColumnIndex(People.NAME); String name = cur.getString(nameColumnIndex); //let’s now see how cwn loop through a cursor while (cur.moveToNext()) { // cursor moved suceessfully //access fields } CONTENT PROVIDER • T o m t Content Provider public class MyProvider extends ContentProvider { private static final String myURI = ”content://com.paad.provider.myapp/items”; public static final Uri CONTENT_URI = Uri.parse(myURI); @Override public boolean onCreate() { //TODO: Construct the underlying database return true; } } CONTENT PROVIDER • Truy xu t thơng tin (thơng qua bi n có tên uriMatcher ) private class final int ALLROWS = 1; private class final int SINGLE_ROWS = 2; private static final UriMatcher uriMatcher; { /*Populate the UriMatcher object, where a URI ending in ‘items’ will correspond to a request for all items, and ‘items/[rowID]’ represents a single row */ static { uriMatcher = new UriMatcher (UriMatcher.NO_MATCH); uriMatcher.addURI (“com.paad.provider.myApp”, “items”, ALLROWS); uriMatcher.addURI (“com.paad.provider.myApp”,“items/#”,SINGLE_ROW); } CONTENT PROVIDER • S d ng UriMatcher CONTENT PROVIDER • Truy v n provider CONTENT PROVIDER • S d ng đ i t ng ContentResolver đ truy xu t vào provider thông qua ph ng th c getContentResolver() CONTENT PROVIDER • Insert Uri vào provider CONTENT PROVIDER • Insert d li u vào provider CONTENT PROVIDER • Delete Uri provider • Delete d li u CONTENT PROVIDER • Update Uri provider • Update d li u CONTENT PROVIDER • S d ng SimpleCursorAdapter o Cho phép g n k t m t Cursor đ n ListView o S d ng layout t đ nh ngh a đ hi n th item • t o m t SimpleCursorAdapter c n: o Context hi n dùng o Layout o Cursor o M t array ch a tên c a c t o M t array ch a ID c a resource cho View hi n th CONTENT PROVIDER String uriString = "content://contacts/people/"; Cursor myCursor = managedQuery(Uri.parse(uriString), null, null, null); String[] fromColumns = new String[] {People.NUMBER, People.NAME}; int[] toLayoutIDs = new int[] {R.id.numberTextView, R.id.nameTextView}; SimpleCursorAdapter myAdapter; myAdapter = new SimpleCursorAdapter(this, R.layout.simplecursorlayout, myCursor, fromColumns, toLayoutIDs); myListView.setAdapter(myAdapter);