MyDatabaseHelper.java 的內(nèi)容如下：
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.widget.Toast;
/**
* Created by toby on 17-12-28.
*/
public class MyDatabaseHelper extends SQLiteOpenHelper {
private static final String CREATE_BOOK = "create table Book (" +
"id integer primary key autoincrement, " +
"author text, " +
"price real, " +
"pages integer, " +
"name text)";
private static final String CREATE_CATEGORY = "create table Category (" +
"id integer primary key autoincrement, " +
"category_name text, " +
"category_code integer)";
private Context mContext;
public MyDatabaseHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,
int version) {
super(context, name, factory, version);
mContext = context;
}
@Override
public void onCreate(SQLiteDatabase sqLiteDatabase) {
sqLiteDatabase.execSQL(CREATE_BOOK);
sqLiteDatabase.execSQL(CREATE_CATEGORY);
Toast.makeText(mContext, "Create succeeded", Toast.LENGTH_SHORT).show();
}
@Override
public void onUpgrade(SQLiteDatabase sqLiteDatabase, int oldVersion, int newVersion) {
switch (oldVersion) {
case 1:
sqLiteDatabase.execSQL(CREATE_CATEGORY);
// 不要加 break脂男，以保證每次數(shù)據(jù)庫的修改都會被執(zhí)行
// break;
case 2:
sqLiteDatabase.execSQL("alter table Book add column category_id integer");
// 不要加 break，以保證每次數(shù)據(jù)庫的修改都會被執(zhí)行
// break;
default:
}
}
}
使用的實(shí)例代碼如下：
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.util.Log;
import android.view.View;
public class MainActivity extends Activity {
private static final String TAG = "MainActivity";
private MyDatabaseHelper dbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
dbHelper = new MyDatabaseHelper(this, "BookStore.db", null, 2);
}
@Override
protected void onDestroy() {
super.onDestroy();
}
public void create(View view) {
dbHelper.getWritableDatabase();
}
public void add(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("name", "The first");
values.put("author", "None");
values.put("pages", 123);
values.put("price", 12.34);
// 第二個參數(shù)用于在未指定添加數(shù)據(jù)的情況下給某些可為空的列自動賦值 NULL煤墙，一般填 null
db.insert("Book", null, values);
values.clear();
values.put("name", "The Second");
values.put("author", "None");
values.put("pages", 234);
values.put("price", 23.45);
db.insert("Book", null, values);
}
public void update(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
ContentValues values = new ContentValues();
values.put("price","10.00");
// 不指定休涤，第三和第四個參數(shù)文兑，將會更新所有行
db.update("Book", values, "name = ?", new String[] {"The first"});
}
public void delete(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
// 第二個和第三個參數(shù)如果不指定將會刪除所有行
db.delete("Book", "pages > ?", new String[] {"200"});
}
public void query(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
Cursor cursor = db.query("Book", null, null, null,
null, null, null);
if (cursor.moveToFirst()) {
do {
String value = cursor.getString(cursor.getColumnIndex("name"));
Log.d(TAG, "Book name is " + value);
value = cursor.getString(cursor.getColumnIndex("author"));
Log.d(TAG, "Book author is " + value);
value = cursor.getString(cursor.getColumnIndex("pages"));
Log.d(TAG, "Book pages is " + value);
value = cursor.getString(cursor.getColumnIndex("price"));
Log.d(TAG, "Book price is " + value);
} while (cursor.moveToNext());
cursor.close();
}
}
public void replace(View view) {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.beginTransaction();
try {
db.delete("Book", null, null);
// if (true) { // 拋出一個異常測試事務(wù)
// throw new NullPointerException();
// }
ContentValues values = new ContentValues();
values.put("name", "The Third");
values.put("author", "Toby");
values.put("pages", 720);
values.put("price", 23.45);
db.insert("Book", null, values);
db.setTransactionSuccessful();
} catch (Exception e) {
e.printStackTrace();
} finally {
db.endTransaction();
}
}
}
布局文件的代碼如下：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
xmlns:app="http://schemas.android.com/apk/res-auto"
xmlns:tools="http://schemas.android.com/tools"
android:layout_width="match_parent"
android:layout_height="match_parent"
tools:context="com.syberos.learnandroid.MainActivity">
<Button
android:id="@+id/create"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentStart="true"
android:layout_alignParentTop="true"
android:layout_marginStart="136dp"
android:layout_marginTop="22dp"
android:text="@string/create"
android:onClick="create"
/>
<Button
android:id="@+id/add"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/create"
android:layout_below="@+id/create"
android:layout_marginTop="17dp"
android:onClick="add"
android:text="@string/add"
/>
<Button
android:id="@+id/update"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/add"
android:layout_below="@+id/add"
android:layout_marginTop="11dp"
android:onClick="update"
android:text="@string/update" />
<Button
android:id="@+id/delete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/update"
android:layout_below="@+id/update"
android:layout_marginTop="15dp"
android:onClick="delete"
android:text="@string/delete" />
<Button
android:id="@+id/query"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/delete"
android:layout_below="@+id/delete"
android:layout_marginTop="14dp"
android:text="@string/query"
android:onClick="query"
/>
<Button
android:id="@+id/replace"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignStart="@+id/query"
android:layout_below="@+id/query"
android:text="@string/replace"
android:onClick="replace"
/>
</RelativeLayout>
string 文件的內(nèi)容如下：
<resources>
<string name="app_name">LearnAndroid</string>
<string name="create">create</string>
<string name="add">add</string>
<string name="update">update</string>
<string name="delete">delete</string>
<string name="query">query</string>
<string name="replace">replace</string>
</resources>
本文參考自 《Android 第一行代碼》
