SQLite數據庫增刪改查
阿新 • • 發佈:2017-11-17
lda writable switch books ide red ear create val
在安卓開發中不可避免的會遇到在手機中保存數據的時候,如果只是小量數據(如保存設置等)的話,用SharedPreferences是個極好的選擇,它以鍵值對的形式保存數據,但是如果數據量比較多的話,比如一個鍵對應了一個集合的情況,此時再用SharedPreferences保存數據就顯得吃力了,如果再需要對數據進行修改刪除的操作,這個保存數據的方法明顯不適合了,所以安卓本身也內置了sqlite數據庫,對於保存app裏面的數據已經夠了。
新建安卓工程後新建一個類:SQLDatabase .java,該類繼承自SQLiteOpenHelper,主要用於新建數據庫,新建數據表和更新數據庫:
1 publicclass SQLDatabase extends SQLiteOpenHelper{ 2 private Context context; 3 private String CREAT_BOOK="create table Book(id integer primary key autoincrement,author text,price real,pages integer,name text)"; 4 public SQLDatabase(Context context, String name, SQLiteDatabase.CursorFactory factory, intversion) { 5 super(context, name, factory, version); 6 this.context = context; 7 } 8 @Override 9 public void onCreate(SQLiteDatabase db) { 10 //建表 11 db.execSQL(CREAT_BOOK); 12 //插入一些數據 13 Toast.makeText(context, "創建數據庫成功", Toast.LENGTH_SHORT).show();14 } 15 @Override 16 public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { 17 Toast.makeText(context, "數據庫更新了", Toast.LENGTH_SHORT).show(); 18 } 19 }
布局文件:
1 <?xml version="1.0" encoding="utf-8"?> 2 <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 3 xmlns:tools="http://schemas.android.com/tools" 4 android:id="@+id/activity_main" 5 android:layout_width="match_parent" 6 android:layout_height="match_parent" 7 android:orientation="vertical" 8 tools:context="com.example.mydiyizho3_2.MainActivity"> 9 <Button 10 android:id="@+id/button1" 11 android:layout_width="match_parent" 12 android:layout_height="wrap_content" 13 android:onClick="onClick" 14 android:text="增"/> 15 <Button 16 android:id="@+id/button2" 17 android:layout_width="match_parent" 18 android:layout_height="wrap_content" 19 android:onClick="onClick" 20 android:text="刪"/> 21 <Button 22 android:id="@+id/button3" 23 android:layout_width="match_parent" 24 android:layout_height="wrap_content" 25 android:onClick="onClick" 26 android:text="改"/> 27 <Button 28 android:id="@+id/button4" 29 android:layout_width="match_parent" 30 android:layout_height="wrap_content" 31 android:onClick="onClick" 32 android:text="查"/> 33 34 </LinearLayout>
接下來就是增加,刪除,修改,查找數據:
1 public class MainActivity extends AppCompatActivity { 2 3 private static final String TAG = "MainActivity"; 4 private SQLDatabase database; 5 private SQLiteDatabase writableDatabase; 6 7 @Override 8 protected void onCreate(Bundle savedInstanceState) { 9 super.onCreate(savedInstanceState); 10 setContentView(R.layout.activity_main); 11 database = new SQLDatabase(MainActivity.this, "BookStore.db", null, 1); 12 } 13 14 public void onClick(View view) { 15 switch (view.getId()){ 16 case R.id.button1://增 17 writableDatabase = database.getWritableDatabase(); 18 ContentValues values = new ContentValues(); 19 for (int i = 0; i <20 ; i++) { 20 values.put("author","homeng"+i); 21 values.put("price",10.5+i); 22 values.put("pages",1000+i); 23 values.put("name","雜技團"+i); 24 long book = writableDatabase.insert("Book", null, values); 25 Log.i(TAG,"每天的id="+book); 26 } 27 //關閉 28 writableDatabase.close(); 29 break; 30 case R.id.button2://刪 31 writableDatabase = database.getWritableDatabase(); 32 int book = writableDatabase.delete("Book", "id=?", new String[]{1 + ""}); 33 Log.i(TAG,"這是刪除的"+book); 34 writableDatabase.close(); 35 break; 36 case R.id.button3://改 37 writableDatabase = database.getWritableDatabase(); 38 ContentValues update = new ContentValues(); 39 update.put("price",10000); 40 int update1 = writableDatabase.update("Book", update, "author=?", new String[]{"homeng5"}); 41 Log.i(TAG,"這是修改的"+update1); 42 writableDatabase.close(); 43 break; 44 case R.id.button4://查 45 writableDatabase = database.getWritableDatabase(); 46 Cursor book1 = writableDatabase.query("Book", null, null, null, null, null, null); 47 if (book1.moveToFirst()){ 48 do { 49 String name = book1.getString(book1.getColumnIndex("name")); 50 float price = book1.getFloat(book1.getColumnIndex("price")); 51 int pages = book1.getInt(book1.getColumnIndex("pages")); 52 String author = book1.getString(book1.getColumnIndex("author")); 53 Log.i(TAG,"name"+name); 54 Log.i(TAG,"price"+price); 55 Log.i(TAG,"pages"+pages); 56 Log.i(TAG,"author"+author); 57 }while (book1.moveToNext()); 58 } 59 writableDatabase.close(); 60 break; 61 } 62 } 63 }
SQLite數據庫增刪改查