Android 高手進階教程(十三)之----Android 數據庫SQLiteDatabase的使用！！
阿新 • • 發佈：2018-08-06
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Android 提供了三種數據存儲方式，第一種是文件存儲;第二種是SharedPreferences 存儲;第三種就是數據庫SQLiteDatabase 存儲。
文件存儲我就不用多說了，而SharedPreferences 可以存取簡單的數據(int,double,float.etc)，它經常用於數據緩存，因為它讀取存儲簡單。詳細可以參見本系列。Android 高手進階教程(七)之----Android 中Preferences的使用!
今天我們將講一下SQLiteDatabase 的使用。 而掌握SqliteDatabase ，將會我們接下來掌握ContentProvider 打下良好的基石。
為了讓大家更好的掌握，我們手把手完成該節的Demo
第一步：新建一個Android工程，命名為SQLiteDatabaseDemo.
第二步:創建一個新的類BooksDB.java 這個類要繼承於android.database.sqlite.SQLiteOpenHelper抽象類，我們要實現其中兩個方法：onCreate(),onUpdate.具體代碼如下：
package com.android.tutor; import android.content.ContentValues; import android.content.Context; import android.database.Cursor; import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteOpenHelper; public class BooksDB extends SQLiteOpenHelper { private final static String DATABASE_NAME = "BOOKS.db"; private final static int DATABASE_VERSION = 1; private final static String TABLE_NAME = "books_table"; public finalstatic String BOOK_ID = "book_id"; public final static String BOOK_NAME = "book_name"; public final static String BOOK_AUTHOR = "book_author"; public BooksDB(Context context) { // TODO Auto-generated constructor stub super(context, DATABASE_NAME, null, DATABASE_VERSION); } //創建table @Override public void onCreate(SQLiteDatabase db) { String sql = "CREATE TABLE " + TABLE_NAME + " (" + BOOK_ID + " INTEGER primary key autoincrement, " + BOOK_NAME + " text, "+ BOOK_AUTHOR +" text);"; db.execSQL(sql); } @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { String sql = "DROP TABLE IF EXISTS " + TABLE_NAME; db.execSQL(sql); onCreate(db); } public Cursor select() { SQLiteDatabase db = this.getReadableDatabase(); Cursor cursor = db .query(TABLE_NAME, null, null, null, null, null, null); return cursor; } //增加操作 public long insert(String bookname,String author) { SQLiteDatabase db = this.getWritableDatabase(); /* ContentValues */ ContentValues cv = new ContentValues(); cv.put(BOOK_NAME, bookname); cv.put(BOOK_AUTHOR, author); long row = db.insert(TABLE_NAME, null, cv); return row; } //刪除操作 public void delete(int id) { SQLiteDatabase db = this.getWritableDatabase(); String where = BOOK_ID + " = ?"; String[] whereValue ={ Integer.toString(id) }; db.delete(TABLE_NAME, where, whereValue); } //修改操作 public void update(int id, String bookname,String author) { SQLiteDatabase db = this.getWritableDatabase(); String where = BOOK_ID + " = ?"; String[] whereValue = { Integer.toString(id) }; ContentValues cv = new ContentValues(); cv.put(BOOK_NAME, bookname); cv.put(BOOK_AUTHOR, author); db.update(TABLE_NAME, cv, where, whereValue); } }
第三步:修改main.xml布局如下，由兩個EditText和一個ListView組成，代碼如下:
<?xml version="1.0" encoding="utf-8"?> <LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" android:orientation="vertical" android:layout_width="fill_parent" android:layout_height="fill_parent" > <EditText android:id="@+id/bookname" android:layout_width="fill_parent" android:layout_height="wrap_content" > </EditText> <EditText android:id="@+id/author" android:layout_width="fill_parent" android:layout_height="wrap_content" > </EditText> <ListView android:id="@+id/bookslist" android:layout_width="fill_parent" android:layout_height="wrap_content" > </ListView> </LinearLayout>
第四步:修改SQLiteDatabaseDemo.java代碼如下:
package com.android.tutor; import android.app.Activity; import android.content.Context; import android.database.Cursor; import android.os.Bundle; import android.view.Menu; import android.view.MenuItem; import android.view.View; import android.view.ViewGroup; import android.widget.AdapterView; import android.widget.BaseAdapter; import android.widget.EditText; import android.widget.ListView; import android.widget.TextView; import android.widget.Toast; public class SQLiteDatabaseDemo extends Activity implements AdapterView.OnItemClickListener { private BooksDB mBooksDB; private Cursor mCursor; private EditText BookName; private EditText BookAuthor; private ListView BooksList; private int BOOK_ID = 0; protected final static int MENU_ADD = Menu.FIRST; protected final static int MENU_DELETE = Menu.FIRST + 1; protected final static int MENU_UPDATE = Menu.FIRST + 2; public void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.main); setUpViews(); } public void setUpViews(){ mBooksDB = new BooksDB(this); mCursor = mBooksDB.select(); BookName = (EditText)findViewById(R.id.bookname); BookAuthor = (EditText)findViewById(R.id.author); BooksList = (ListView)findViewById(R.id.bookslist); BooksList.setAdapter(new BooksListAdapter(this, mCursor)); BooksList.setOnItemClickListener(this); } @Override public boolean onCreateOptionsMenu(Menu menu) { super.onCreateOptionsMenu(menu); menu.add(Menu.NONE, MENU_ADD, 0, "ADD"); menu.add(Menu.NONE, MENU_DELETE, 0, "DELETE"); menu.add(Menu.NONE, MENU_DELETE, 0, "UPDATE"); return true; } public boolean onOptionsItemSelected(MenuItem item) { super.onOptionsItemSelected(item); switch (item.getItemId()) { case MENU_ADD: add(); break; case MENU_DELETE: delete(); break; case MENU_UPDATE: update(); break; } return true; } public void add(){ String bookname = BookName.getText().toString(); String author = BookAuthor.getText().toString(); //書名和作者都不能為空，或者退出 if (bookname.equals("") || author.equals("")){ return; } mBooksDB.insert(bookname, author); mCursor.requery(); BooksList.invalidateViews(); BookName.setText(""); BookAuthor.setText(""); Toast.makeText(this, "Add Successed!", Toast.LENGTH_SHORT).show(); } public void delete(){ if (BOOK_ID == 0) { return; } mBooksDB.delete(BOOK_ID); mCursor.requery(); BooksList.invalidateViews(); BookName.setText(""); BookAuthor.setText(""); Toast.makeText(this, "Delete Successed!", Toast.LENGTH_SHORT).show(); } public void update(){ String bookname = BookName.getText().toString(); String author = BookAuthor.getText().toString(); //書名和作者都不能為空，或者退出 if (bookname.equals("") || author.equals("")){ return; } mBooksDB.update(BOOK_ID, bookname, author); mCursor.requery(); BooksList.invalidateViews(); BookName.setText(""); BookAuthor.setText(""); Toast.makeText(this, "Update Successed!", Toast.LENGTH_SHORT).show(); } @Override public void onItemClick(AdapterView<?> parent, View view, int position, long id) { mCursor.moveToPosition(position); BOOK_ID = mCursor.getInt(0); BookName.setText(mCursor.getString(1)); BookAuthor.setText(mCursor.getString(2)); } public class BooksListAdapter extends BaseAdapter{ private Context mContext; private Cursor mCursor; public BooksListAdapter(Context context,Cursor cursor) { mContext = context; mCursor = cursor; } @Override public int getCount() { return mCursor.getCount(); } @Override public Object getItem(int position) { return null; } @Override public long getItemId(int position) { return 0; } @Override public View getView(int position, View convertView, ViewGroup parent) { TextView mTextView = new TextView(mContext); mCursor.moveToPosition(position); mTextView.setText(mCursor.getString(1) + "___" + mCursor.getString(2)); return mTextView; } } }
第五步:運行程序效果如下:
第六步：查看我們所建的數據庫。有兩種方法：第一種用命令查看：adb shell ls data/data/com.android.tutor/databases。
另一種方法是用DDMS查看，在data/data下面對應的應用程序的包名 下會有如下數據庫，如圖所示：
Android 高手進階教程(十三)之----Android 數據庫SQLiteDatabase的使用！！