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Chapter 8

Chapter 8. Saving and Reading Files. Java I/O. Write a Text File. FileWriter FileWriter 寫入單位為 char 。產生物件方式如下： 在 FileWriter 物件參數當中，第一個為檔案名稱，第二個為寫入模式是否為 append BufferedWriter 使用 Buffer 機制來做 write() 時，會先將要寫入之檔案暫存起來，等到一定的資料量後才寫入磁碟，因此可省下不少 I/O 所造成的負擔。. Write a Text File.

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Chapter 8

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  1. Chapter 8 Saving and Reading Files

  2. Java I/O

  3. Write a Text File • FileWriter • FileWriter寫入單位為char。產生物件方式如下： • 在FileWriter物件參數當中，第一個為檔案名稱，第二個為寫入模式是否為append • BufferedWriter • 使用Buffer機制來做write()時，會先將要寫入之檔案暫存起來，等到一定的資料量後才寫入磁碟，因此可省下不少I/O所造成的負擔。

  4. Write a Text File The most applied methods of BufferedWriter

  5. Write a Text File Results of the example are shown below：

  6. Write a Text File public class JavaWriteData extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); try { // 建立FileWriter物件，並將寫入位置設定為SD卡中的output.txt FileWriter fw = new FileWriter( "/sdcard/output.txt", false ); // 建立fw的Output Buffer BufferedWriter bw = new BufferedWriter( fw ); bw.write("Hello, Android"); bw.newLine(); bw.close(); } catch (IOException e) { e.printStackTrace(); } } } Codes are as below：

  7. File Stream Output • FileOutputStream • 此種方式是以byte為單位對檔案作存取，故通常在使用這種方式來做檔案讀寫時會一起使用其他Object的OutputStream，目的是將我們要儲存的目標檔案自動以byte的形式作儲存

  8. File Stream Output Results of the example are shown below ：

  9. File Stream Output public class JavaOutputStream extends Activity { /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); try { String data1 = "This is OutputStream data"; String data2 = "\n"; FileOutputStream output = new FileOutputStream("/sdcard/output.txt"); output.write(data1.getBytes()); output.write(data2.getBytes()); output.close(); } catch (Exception e) { e.printStackTrace(); } } } Codes are as below ：

  10. Read a Text File • FileReader • FileReader讀取單位為char。產生物件方式如下： • BufferedReader

  11. Read a Text File The most applied methods of BufferedWriter

  12. Read a Text File Results of the example are shown below ：

  13. Read a Text File public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); try { // 建立FileReader物件，設定讀取的檔案為SD卡中的output.txt FileReader fr = new FileReader( "/sdcard/output.txt" ); // 建立fr的Input Buffer BufferedReader br = new BufferedReader( fr ); String readData = ""; String temp = br.readLine(); while( temp != null ) { readData += temp; temp = br.readLine(); } Context context = getApplicationContext(); int duration = Toast.LENGTH_LONG; Toast toast = Toast.makeText(context, readData, duration); toast.show(); } catch (Exception e) { e.printStackTrace(); } } Codes are as below：

  14. File Stream Input • FileInputStream • 此種方式如同FileOutputStream是以byte為單位，故此方法通常也用於不同物件的讀取

  15. File Stream Input Results of the example are shown below ：

  16. File Stream Input public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); try { FileInputStream input = new FileInputStream("/sdcard/output.txt"); String data = ""; while (input.available() > 0) { byte [] b = new byte[10]; if ( input.read(b) != -1 ) data += new String(b); else break; } Context context = getApplicationContext(); int duration = Toast.LENGTH_LONG; Toast toast = Toast.makeText(context, data, duration); toast.show(); } catch (Exception e) { e.printStackTrace(); } } Codes are as below：

  17. SQLite

  18. SQLite • Features of SQLite ： • 不需要一個額外的系統來運行整個資料庫系統 • 寫入或是讀取資料都是直接連結到檔案中 • 由於都以檔案型式存在，所以可以將此資料隨意在大部分平台下使用 • 支援大部分SQL92的語法 • 運行資料庫操作時所佔用的資源較小

  19. Introduction on SQL Language • CREATE TABLE • Create table用來建立表格，而表格分為列（row）和欄（column），而表格當中的資料可以有不同的資料型態

  20. Introduction on SQL Language • CREATE TABLE Example

  21. Introduction on SQL Language Results of CREATE TABLEExample：

  22. Introduction on SQL Language • ALTER TABLE • Alter table用來更改Table，如新增、刪除、更改欄位屬性或名稱，更改指令如下表： • Using method of Alter table is shown below：

  23. Introduction on SQL Language • DROP TABLE • Drop table指令為刪除一個表格，其用法如下：

  24. Introduction on SQL Language • INSERT • Insert指令用於將資料輸入到表格當中，使用方法如下：

  25. Introduction on SQL Language • SELECT • Select指令用於查詢資料庫當中符合條件的資料，使用方法如下：

  26. Introduction on SQL Language • UPDATE • Update指令可修改資料表當中的值，使用方法如下：

  27. Introduction on SQL Language • DELETE • Delete指令可將符合條件的資料給刪除，使用方法如下：

  28. Introduction on SQL Language 使用adb工具進入模擬器中，接著在模擬器當中使用sqlite3這個工具，使用方法為：

  29. SQLite Development–EX1 src/ncu/bnlab/MyDatabase.java public class MyDatabase extends SQLiteOpenHelper { public MyDatabase(Context context, String name, CursorFactory factory,int version) { super(context, name, factory, version); } @Override public void onCreate(SQLiteDatabase db) { // TODO Auto-generated method stub } @Override public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) { // TODO Auto-generated method stub } }

  30. SQLite Development–EX1 src/ncu/bnlab/sqliteExample.java public class sqliteExample extends Activity { // 設定DATABASE檔案名稱 private final String DATABASE_NAME = "example1"; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); MyDatabase myDBHelper = new MyDatabase(this, DATABASE_NAME, null, 3); }

  31. SQLite Development–EX2 src/ncu/bnlab/MyDatabase.java public class MyDatabase extends SQLiteOpenHelper{ public String DATABASE_TABLE = "STUDENTINFO"; public final String DB_CREATE_TABLE = "CREATE TABLE " + DATABASE_TABLE + "( " + "ID INTEGER NOT NULL," + "NAME CHAR(20) NOT NULL," + "PHONE CHAR(20)," + "CLASS CHAR(50)," + "PRIMARY KEY(ID) );"; public MyDatabase(Context context, String name, CursorFactory factory, int version) { super(context, name, factory, version); } @Override public void onCreate(SQLiteDatabase db) { db.execSQL(DB_CREATE_TABLE); } @Override public void onUpgrade(SQLiteDatabase db, int arg1, int arg2) { // TODO Auto-generated method stub db.execSQL("DROP IF TABLE EXISTS " + DATABASE_TABLE); onCreate(db); } }

  32. SQLite Development–EX4 src/ncu/bnlab/sqliteExample.java public class sqliteExample extends Activity { private final String DATABASE_NAME = "example1"; @Override public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); MyDatabase myDBHelper = new MyDatabase(this, DATABASE_NAME, null, 3); SQLiteDatabase db = myDBHelper.getWritableDatabase(); // 搜尋STUDENTINFO資料表中的資料 String cmd = "SELECT * FROM STUDENTINFO;"; Cursor result = db.rawQuery(cmd, null); result.moveToNext(); // 將結果以AlertDialog的方式輸出 for( int i = 0; i < result.getColumnCount() ;i++ ) { String data = result.getString(i); AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage(data); builder.show(); } } }

  33. SQLite Development The most used Cursor are listed below:

  34. SQLite Development The most used Cursor are listed below:

  35. Q&A

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