android 之數據庫sqlite 使用

  初步嘗試sqlite 確實比較輕量級，功能強大，支持五種數據類型，NULL、INTEGER、REAL(浮點型)、TEXT(字符文本型),sqlite 最大特點就是可以保存任何類型的數據到任何字段中，而無論這列聲明的數據類型是什麼，如 ： 可以在Integer 類型存放字符串，有一種情況除外： 定義爲integer primary key 的字段只能存儲64位整數，如果像其保存整數以外的數據會產生錯誤

    與關係型數據庫相比sqlite 最大限制除了字段無類型外，就是不支持外鍵約束，當然就不支持表連接了

對於sqlite 比較重要的類

SQLiteOpenHelper 他是一個輔助類，用來管理數據庫的創建和數據庫的版本。通過繼承這個類，實現他的一些方法對數據庫進行操作

SQLiteDataBase 代表一個數據庫對象，主要有create（） execSQL() 以及 beginTransaction() endTransaction() 

SQLiteCursor 代表查詢結果的記錄集，主要操作MoveFirst() MoveLast() MoveNext() Move()  IsLast() GetColumns() 

    實現增，刪，改，查，代碼如下

main.xml

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".MainActivity"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/counttip"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text="@string/hello" />

    <ListView
        android:id="@+id/ListView01"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"></ListView>

</LinearLayout>

main.java

package com.example.i18n;

import android.os.Bundle;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.util.Log;
import android.widget.ListAdapter;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
import android.widget.TextView;

public class MainActivity extends Activity {

    private static final String TAG = MainActivity.class.getSimpleName();

    private ListView lv = null;
    private TextView tv = null;
    private SQLiteDatabase mSQLiteDatabase;
    private static final String DATABASE_NAME = "Test.db";
    private static final String TABLE_NAME = "table_test";
    private static final String COLUMN_ID = "_id"; // primary key
    private static final String COLUMN_NAME = "name";
    private static final String COLUMN_AGE = "age";
    private static final String CREATE_TABLE = "create table if not exists " + TABLE_NAME + "(" + COLUMN_ID + " integer primary key,"
                                                        + COLUMN_NAME + " text," + COLUMN_AGE + " integer)";

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        lv = (ListView) this.findViewById(R.id.ListView01);
        tv = (TextView) this.findViewById(R.id.counttip);

        try {
            mSQLiteDatabase = this.openOrCreateDatabase(DATABASE_NAME, Activity.MODE_PRIVATE, null);
        } catch (Exception ex) {
            Log.e(TAG, "打開或者創建數據庫異常" + ex.getMessage());
        }

        try {
            mSQLiteDatabase.execSQL(CREATE_TABLE);
        } catch (Exception ex) {
            Log.e(TAG, "創建表異常" + ex.getMessage());
        }
        insertData();
        insertData2();
        this.selectData();
    }


    @Override
    protected void onPause() {
        super.onPause();
        mSQLiteDatabase.close();
    }

    /**
     * 插入數據
     */
    private void insertData() {
        try {
            String sql = "insert into " + TABLE_NAME + "(" + COLUMN_NAME + "," + COLUMN_AGE + ") values('張三',30)";
            mSQLiteDatabase.execSQL(sql);
        } catch (Exception e) {
            Log.e(TAG,"插入數據異常" + e.getMessage());
        }
    }

    /**
     * 插入數據2
     */
    private void insertData2() {
        try {
            String sql = "insert into " + TABLE_NAME + "(" + COLUMN_NAME + "," + COLUMN_AGE + ") values(?,?)";
            Object [] ob = new Object[]{"王五",50};
            mSQLiteDatabase.execSQL(sql,ob);
        } catch (Exception e) {
            Log.e(TAG,"插入數據異常" + e.getMessage());
        }
    }

    private void addData() {
        try {
            ContentValues cv = new ContentValues();
            cv.put(COLUMN_NAME, "李四");
            cv.put(COLUMN_AGE, 40);
            long num = mSQLiteDatabase.insertOrThrow(TABLE_NAME, null, cv);
            setTitle("num == " + num);
        } catch (Exception e) {
            Log.e(TAG,"插入數據異常" + e.getMessage());
        }
    }

    /**
     * 更新數據
     */
    private void updateData() {
        try {
            String str = "update " + TABLE_NAME + " set " + COLUMN_AGE + "=25 where id=1";
            mSQLiteDatabase.execSQL(str);
        } catch (Exception e) {
            Log.e(TAG,"更新數據異常" + e.getMessage());
        }
    }
    private void updateData2() {
        try {
            String str = "update " + TABLE_NAME + " set " + COLUMN_AGE + "=? where id=?";
            Object[] ob = new Object[]{33,2};
            mSQLiteDatabase.execSQL(str);
        } catch (Exception e) {
            Log.e(TAG,"更新數據異常" + e.getMessage());
        }
    }
    private void updateData3() {
        try {
            ContentValues cv = new ContentValues();
            cv.put(COLUMN_NAME, "李四");
            cv.put(COLUMN_AGE, 43);
            long num = mSQLiteDatabase.update(TABLE_NAME, cv ,COLUMN_NAME + "=?",new String[]{"李四"});
            setTitle("修改行數 num= " + num);
        } catch (Exception e) {
            Log.e(TAG,"更新數據異常" + e.getMessage());
        }
    }

    /**
     * 刪除數據
     */
    private void deleteData() {
        try{
            String sql = "delete from " + TABLE_NAME +  " where _id=3";
            mSQLiteDatabase.execSQL(sql);
        } catch(Exception e) {
            Log.e(TAG,"刪除數據異常" + e.getMessage());
        }
    }

    private void deleteData2() {
        try{
            String sql = "delete from " + TABLE_NAME +  " where _id=?";
            mSQLiteDatabase.execSQL(sql,new Object[]{2});
        } catch(Exception e) {
            Log.e(TAG,"刪除數據異常" + e.getMessage());
        }
    }

    private void deleteData3() {
        try{
            int num = mSQLiteDatabase.delete(TABLE_NAME, "_id=1", null);
            setTitle("刪除行數 num= " + num);
        } catch(Exception e) {
            Log.e(TAG,"刪除數據異常" + e.getMessage());
        }
    }

    /**
     * 查詢數據
     */
    private void selectData() {
        try{
            String sql = "select * from " + TABLE_NAME;
            Cursor curson = mSQLiteDatabase.rawQuery(sql, null);
            if(curson !=null) {
                ListAdapter adapter = new SimpleCursorAdapter(this, R.layout.list,curson, new String[]{COLUMN_ID,COLUMN_NAME,COLUMN_AGE}, new int[]{R.id.textView1,R.id.textView2,R.id.textView3});
                lv.setAdapter(adapter);
                tv.setText(Integer.toString(curson.getCount()));
            }
        } catch (Exception e) {
            Log.e(TAG, "查詢數據異常" + e.getMessage());
        }
    }

    /**
     * 刪除表
     */
    private void dropTable() {
        try{
            String sql = "drop table " + TABLE_NAME;
            mSQLiteDatabase.execSQL(sql);
        } catch(Exception e) {
            Log.e(TAG, "刪除數據異常" + e.getMessage());
        }
    }

    /**
     * 刪除數據庫
     */
    private void dropDataBase() {
        try{
            deleteDatabase(DATABASE_NAME);
        } catch (Exception ex) {
            Log.e(TAG, "刪除數據庫異常 "+ ex.getMessage());
        }
    }
}

list.xml

<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:orientation="vertical" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""/>

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""/>

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:text=""/>

</LinearLayout>