Android - Data Storage
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The document discusses various data storage options for Android applications, including shared preferences, internal and external file storage, and SQLite databases. It provides code examples for reading and writing data to shared preferences files and internal storage, as well as implementing a SQLite database using SQLiteOpenHelper and performing common CRUD operations.
![• DatabaseUXls.java
public
ArrayList<Classmate>
getClassmateList()
{
if(isOpen()
==
false)
{
openDatabase();
}
ArrayList<Classmate>
list
=
new
ArrayList<Classmate>();
String
name,
descripXon;
int
imgRes;
Cursor
cursor
=
mDb.query(DatabaseConsts.TABLE_NAME,
new
String[]
{},
null,
null,
null,
null,
null);
if(cursor
==
null)
{
Log.e(TAG,
"Invalid
query.");
return
list;
}
try
{
while(cursor.moveToNext())
{
name
=
cursor.getString(cursor.getColumnIndex(DatabaseConsts.NAME));
descripXon
=
cursor.getString(cursor.getColumnIndex(DatabaseConsts.DESCRIPTION));
imgRes
=
cursor.getInt(cursor.getColumnIndex(DatabaseConsts.IMAGE_RESOURCE));
list.add(new
Classmate(name,
descripXon,
imgRes));
}
}
catch(ExcepXon
e)
{
Log.i(TAG,
"Search
classmate
table
error
"
+
e.toString());
}
finally
{
cursor.close();
}
closeDatabase();
return
list;
2014/9/9
}
Copyright
©
2014
MingHo
Chang](https://image.slidesharecdn.com/android-datastorage-140909081135-phpapp01/85/Android-Data-Storage-31-320.jpg)
![• DatabaseUXls.java
public
Classmate
getClassmate(String
name)
{
if(isOpen()
==
false)
{
openDatabase();
}
Classmate
c
=
null;
String
descripXon;
int
imgRes;
Cursor
cursor
=
mDb.query(DatabaseConsts.TABLE_NAME,
new
String[]
{},
DatabaseConsts.NAME
+
"
=
'"
+
name
+
"'",
null,
null,
null,
null);
if(cursor
==
null)
{
Log.e(TAG,
"Invalid
query.");
return
null;
}
try
{
while(cursor.moveToNext())
{
descripXon
=
cursor.getString(cursor.getColumnIndex(DatabaseConsts.DESCRIPTION));
imgRes
=
cursor.getInt(cursor.getColumnIndex(DatabaseConsts.IMAGE_RESOURCE));
c
=
new
Classmate(name,
descripXon,
imgRes);
}
}
catch(ExcepXon
e)
{
Log.i(TAG,
"Search
classmates
table
error
"
+
e.toString());
}
finally
{
cursor.close();
}
closeDatabase();
return
c;
2014/9/9
}
Copyright
©
2014
MingHo
Chang](https://image.slidesharecdn.com/android-datastorage-140909081135-phpapp01/85/Android-Data-Storage-32-320.jpg)
Android - Data Storage
- 1. Data Storage 2014/9/9 Copyright © 2014 MingHo Chang
- 2. 張明禾 • C • Android App • NodeJS • Sencha Touch • Unity 2014/9/9 Copyright © 2014 MingHo Chang
- 3. Data Storage • Shared preferences files – Saving key-‐value pairs of simple data. – Private or shared • Android file system – Saving arbitrary files. – Read/Write in order. • Database – Saving structured data. 2014/9/9 Copyright © 2014 MingHo Chang
- 4. SharedPreferences • Key-‐value pair of data • Can be either private or shared 2014/9/9 Copyright © 2014 MingHo Chang
- 5. SharedPreferences – Get handle • Use only one shared preferences file – PreferenceManager.getDefaultPreferences(context) – getPreferences(Context.MODE_PRIVATE) • Use mulXple shared preferences files – getSharedPreferences(FILE_KEY, Context.MODE_PRIVATE) • Example SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(mCo ntext); 2014/9/9 Copyright © 2014 MingHo Chang
- 6. SharedPreferences • Accessibility – MODE_PRIVATE – MODE_WORLD_READABLE – MODE_WORLD_WRITEABLE 2014/9/9 Copyright © 2014 MingHo Chang
- 7. SharedPreferences – Write • SharedPreferences.Editor SharedPreferences.Editor editor = sharedPref.edit(); editor.putInt(“saved_high_score”, 100); editor.commit(); 2014/9/9 Copyright © 2014 MingHo Chang
- 8. SharedPreferences – Read int defaultValue = 60; int highScore = sharedPref.getInt(“saved_high_score”, defaultValue); 2014/9/9 Copyright © 2014 MingHo Chang
- 9. SharedPreferences • FirstAcXvity.java SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences(mContext); SharedPreferences.Editor editor = sharedPref.edit(); for(int i = 0; i < mClassmates.size(); i++) { String name = mClassmates.get(i).name; if(sharedPref.contains(name) == true) { if(sharedPref.getBoolean(name, false) == true) { // Toast name + “has been updated” } } else { editor.putBoolean(name, false); } } editor.commit(); 2014/9/9 Copyright © 2014 MingHo Chang
- 10. SharedPreferences • SecondAcXvity.java SharedPreferences sharedPref = PreferenceManager.getDefaultSharedPreferences( mContext); SharedPreferences.Editor editor = sharedPref.edit(); editor.putBoolean(mName, true); editor.commit(); 2014/9/9 Copyright © 2014 MingHo Chang
- 11. 1st ImplementaXon • Save update status of every classmate in default shared preferences file. • Toast classmates’ names that have been updated when the app starts. 2014/9/9 Copyright © 2014 MingHo Chang
- 12. File • Internal Storage – Accessible by only your app by default. – Removed when your app is uninstalled. • External Storage – World-‐readable 2014/9/9 Copyright © 2014 MingHo Chang
- 13. File – Internal Storage String filename = "myfile”, str = "Hello world!"; FileOutputStream outputStream; try { outputStream = openFileOutput(filename, Context.MODE_PRIVATE); outputStream.write(str.getBytes()); outputStream.close(); } catch (ExcepXon e) { e.printStackTrace(); } 2014/9/9 Copyright © 2014 MingHo Chang
- 14. File – External Storage • Permission <manifest ...> <uses-‐permission android:name="android.permission.WRITE_EXTERN AL_STORAGE" /> <uses-‐permission android:name="android.permission.READ_EXTERNA L_STORAGE" /> ... </manifest> 2014/9/9 Copyright © 2014 MingHo Chang
- 15. File – External Storage • Verify that the volume is available before accessing it – getExternalStorageState() • Environment.MEDIA_MOUNTED • Environment.MEDIA_MOUNTED_READ_ONLY 2014/9/9 Copyright © 2014 MingHo Chang
- 16. File – External Storage • Public files Environment.getExternalStoragePublicDirectory(Env ironment.DIRECTORY_PICTURES) • Private files context.getExternalFilesDir(Environment.DIRECTOR Y_PICTURES) 2014/9/9 Copyright © 2014 MingHo Chang
- 17. File – Delete • myFile.delete(); • context.deleteFile(fileName); 2014/9/9 Copyright © 2014 MingHo Chang
- 18. Database(SQLite) – Structure • Constants • SQLiteOpenHelper • OperaXons 2014/9/9 Copyright © 2014 MingHo Chang
- 19. Database(SQLite) -‐ Constants • DATABASE_NAME • DATABASE_VERSION • Table field names 2014/9/9 Copyright © 2014 MingHo Chang
- 20. Database(SQLite) -‐ Constants • DatabaseConsts.java public class DatabaseConsts implements BaseColumns { public final staXc String DATABASE_NAME = "android.db"; public final staXc int DATABASE_VERSION = 1; public final staXc String TABLE_NAME = "classmates"; public final staXc String NAME = "name"; public final staXc String DESCRIPTION = "descripXon"; public final staXc String IMAGE_RESOURCE = "image_resource"; } 2014/9/9 Copyright © 2014 MingHo Chang
- 21. Database(SQLite) – SQLiteOpenHelper • Create table – onCreate() • Upgrade table – onUpgrade() 2014/9/9 Copyright © 2014 MingHo Chang
- 22. Database(SQLite) – SQLiteOpenHelper • DatabaseHelper.java public class DatabaseHelper extends SQLiteOpenHelper { public DatabaseHelper(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); } @Override public void onCreate(SQLiteDatabase db) { createTable(db); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { dropTable(db); onCreate(db); } } 2014/9/9 Copyright © 2014 MingHo Chang
- 23. Database(SQLite) – SQLiteOpenHelper • DatabaseHelper.java private void createTable(SQLiteDatabase db) { db.execSQL("CREATE TABLE IF NOT EXISTS " + DatabaseConsts.TABLE_NAME + " (” + DatabaseConsts._ID + " INTEGER PRIMARY KEY,” + DatabaseConsts.NAME + " TEXT,” + DatabaseConsts.DESCRIPTION + " TEXT,” + DatabaseConsts.IMAGE_RESOURCE + " INTEGER” + ");"); } 2014/9/9 Copyright © 2014 MingHo Chang
- 24. Database(SQLite) – SQLiteOpenHelper • DatabaseHelper.java public void dropTable(SQLiteDatabase db) { db.execSQL("DROP TABLE IF EXISTS " + DatabaseConsts.TABLE_NAME); } 2014/9/9 Copyright © 2014 MingHo Chang
- 25. Database(SQLite) – OperaXons • Open database • Insert data • Update data • Get data • Delete data 2014/9/9 Copyright © 2014 MingHo Chang
- 26. Database(SQLite) – OperaXons • DatabaseUXls.java public class DatabaseUXls { private staXc final String TAG = DatabaseUXls.class.getSimpleName(); private DatabaseHelper mDbHelper; private SQLiteDatabase mDb = null; private Context mContext; public DatabaseUXls(Context context) { mContext = context; mDbHelper = new DatabaseHelper(mContext, DatabaseConsts.DATABASE_NAME, null, DatabaseConsts.DATABASE_VERSION); 2014/9/9} Copyright © 2014 MingHo Chang
- 27. Database(SQLite) – OperaXons • DatabaseUXls.java private boolean isOpen() { if(mDb == null) { return false; } return mDb.isOpen(); } private void openDatabase() { if(isOpen() == false) { mDb = mDbHelper.getWritableDatabase(); } } public void closeDatabase() { mDb.close(); 2014/9/9 } Copyright © 2014 MingHo Chang
- 28. • DatabaseUXls.java public boolean insertData(ArrayList<Classmate> classmates) { if(isOpen() == false) { openDatabase(); } long count = 0; try { mDb.beginTransacXon(); for(Classmate c : classmates) { ContentValues values = new ContentValues(); values.put(DatabaseConsts.NAME, c.name); values.put(DatabaseConsts.DESCRIPTION, c.descripXon); values.put(DatabaseConsts.IMAGE_RESOURCE, c.imageRes); count = mDb.insert(DatabaseConsts.TABLE_NAME, null, values); } mDb.setTransacXonSuccessful(); } catch(ExcepXon e) { Log.i(TAG, e.toString()); } finally { mDb.endTransacXon(); } closeDatabase(); return count > 0; } 2014/9/9 Copyright © 2014 MingHo Chang
- 29. • DatabaseUXls.java public boolean deleteData(ArrayList<Classmate> classmates) { if(isOpen() == false) { openDatabase(); } long count = 0; try { mDb.beginTransacXon(); for(Classmate c : classmates) { count = mDb.delete(DatabaseConsts.TABLE_NAME, DatabaseConsts.NAME + " = '" + c.name + "'", null); } mDb.setTransacXonSuccessful(); } catch(ExcepXon e) { Log.i(TAG, e.toString()); } finally { mDb.endTransacXon(); } closeDatabase(); return count > 0; 2014/9/9 } Copyright © 2014 MingHo Chang
- 30. • DatabaseUXls.java public boolean updateData(Classmate classmate) { if(isOpen() == false) { openDatabase(); } long count = 0; try { mDb.beginTransacXon(); ContentValues values = new ContentValues(); values.put(DatabaseConsts.NAME, classmate.name); values.put(DatabaseConsts.DESCRIPTION, classmate.descripXon); values.put(DatabaseConsts.IMAGE_RESOURCE, classmate.imageRes); count = mDb.update(DatabaseConsts.TABLE_NAME, values, DatabaseConsts.NAME + " = '" + classmate.name + "'", null); mDb.setTransacXonSuccessful(); } catch(ExcepXon e) { Log.i(TAG, e.toString()); } finally { mDb.endTransacXon(); } closeDatabase(); return count > 0; } 2014/9/9 Copyright © 2014 MingHo Chang
- 31. • DatabaseUXls.java public ArrayList<Classmate> getClassmateList() { if(isOpen() == false) { openDatabase(); } ArrayList<Classmate> list = new ArrayList<Classmate>(); String name, descripXon; int imgRes; Cursor cursor = mDb.query(DatabaseConsts.TABLE_NAME, new String[] {}, null, null, null, null, null); if(cursor == null) { Log.e(TAG, "Invalid query."); return list; } try { while(cursor.moveToNext()) { name = cursor.getString(cursor.getColumnIndex(DatabaseConsts.NAME)); descripXon = cursor.getString(cursor.getColumnIndex(DatabaseConsts.DESCRIPTION)); imgRes = cursor.getInt(cursor.getColumnIndex(DatabaseConsts.IMAGE_RESOURCE)); list.add(new Classmate(name, descripXon, imgRes)); } } catch(ExcepXon e) { Log.i(TAG, "Search classmate table error " + e.toString()); } finally { cursor.close(); } closeDatabase(); return list; 2014/9/9 } Copyright © 2014 MingHo Chang
- 32. • DatabaseUXls.java public Classmate getClassmate(String name) { if(isOpen() == false) { openDatabase(); } Classmate c = null; String descripXon; int imgRes; Cursor cursor = mDb.query(DatabaseConsts.TABLE_NAME, new String[] {}, DatabaseConsts.NAME + " = '" + name + "'", null, null, null, null); if(cursor == null) { Log.e(TAG, "Invalid query."); return null; } try { while(cursor.moveToNext()) { descripXon = cursor.getString(cursor.getColumnIndex(DatabaseConsts.DESCRIPTION)); imgRes = cursor.getInt(cursor.getColumnIndex(DatabaseConsts.IMAGE_RESOURCE)); c = new Classmate(name, descripXon, imgRes); } } catch(ExcepXon e) { Log.i(TAG, "Search classmates table error " + e.toString()); } finally { cursor.close(); } closeDatabase(); return c; 2014/9/9 } Copyright © 2014 MingHo Chang
- 33. • DatabaseUXls.java public boolean cleanTable() { if(isOpen() == false) { openDatabase(); } long count = 0; try { mDb.beginTransacXon(); count = mDb.delete(DatabaseConsts.TABLE_NAME, null, null); mDb.setTransacXonSuccessful(); } catch(ExcepXon e) { Log.i(TAG, e.toString()); } finally { mDb.endTransacXon(); } closeDatabase(); return count > 0; 2}0 14/9/9 Copyright © 2014 MingHo Chang
- 34. Database(SQLite) – OperaXons • DatabaseUXls.java public void deleteTable() { mDbHelper.dropTable(mDb); mDbHelper.createTable(mDb); } 2014/9/9 Copyright © 2014 MingHo Chang
- 35. Database(SQLite) – Insert Data • FirstAcXvity.java -‐> onCreate() mDU = new DatabaseUXls(mContext); if(sharedPref.contains("database_inited") == false || sharedPref.getBoolean("database_inited", false) == false) { initDatabase(); editor.putBoolean("database_inited", true); editor.commit(); } mClassmates = mDU.getClassmateList(); mListAdapter = new CustomAdapter(this, mClassmates); mList.setAdapter(mListAdapter); 2014/9/9 Copyright © 2014 MingHo Chang
- 36. Database(SQLite) – Insert Data • FirstAcXvity.java private void initDatabase() { ArrayList<Classmate> classmates = new ArrayList<Classmate>(); classmates.add(new Classmate("Mary", "A girl.", R.drawable.person_1)); classmates.add(new Classmate("Tom", "A boy.", R.drawable.person_1)); classmates.add(new Classmate("Mark", "A boy.", R.drawable.person_1)); classmates.add(new Classmate("Cindy", "A girl.", R.drawable.person_1)); classmates.add(new Classmate("Tiffany", "A girl.", R.drawable.person_1)); classmates.add(new Classmate("John", "A boy.", R.drawable.person_1)); classmates.add(new Classmate("Amy", "A girl.", R.drawable.person_1)); classmates.add(new Classmate("Annie", "A girl.", R.drawable.person_1)); classmates.add(new Classmate("Jimmy", "A boy.", R.drawable.person_1)); classmates.add(new Classmate("Eddie", "A boy.", R.drawable.person_1)); mDU.insertData(classmates); } 2014/9/9 Copyright © 2014 MingHo Chang
- 37. 2nd ImplementaXon • Use database to hold data. 2014/9/9 Copyright © 2014 MingHo Chang
- 38. Database(SQLite) – Update Data • FirstAcXvity.java -‐> CustomReceiver -‐> onReceive updateDatabase(mClassmates.get(posiXon)); • FirstAcXvity.java private void updateDatabase(Classmate classmate) { mDU.updateData(classmate); } 2014/9/9 Copyright © 2014 MingHo Chang
- 39. 3rd ImplementaXon • Update data to database. 2014/9/9 Copyright © 2014 MingHo Chang