android之SQLlite操作

布局文件

创建了四个按键，分别对应增删改查

<?xml version="1.0" encoding="utf-8"?>
<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"
android:orientation="vertical"
tools:context="xidian.dy.com.chujia.MainActivity">
<Button
android:id="@+id/btn_insert"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="插入一条数据"/>
<Button
android:id="@+id/btn_query"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="查询当前数据" />
<Button
android:id="@+id/btn_update"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="修改一条数据"/>
<Button
android:id="@+id/btn_delete"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:text="删除一条数据"/>
</LinearLayout>

数据库操作

package xidian.dy.com.chujia;

import android.content.ContentValues;
import android.database.Cursor;
import android.database.sqlite.SQLiteDatabase;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends AppCompatActivity implements View.OnClickListener {

private SQLiteDatabase db;
private MainActivity mContext;
private int i = 1;

@Override
protected void onCreate(Bundle savedInstanceState) {
mContext = MainActivity.this;
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
MyDBOpenHelper myDBHelper = new MyDBOpenHelper(mContext, "my.db", null, 1);
db = myDBHelper.getWritableDatabase();
bindViews();
}

private void bindViews() {
Button btn_insert = (Button) findViewById(R.id.btn_insert);
Button btn_query = (Button) findViewById(R.id.btn_query);
Button btn_update = (Button) findViewById(R.id.btn_update);
Button btn_delete = (Button) findViewById(R.id.btn_delete);
if(btn_query != null)
btn_query.setOnClickListener(this);
if(btn_insert != null)
btn_insert.setOnClickListener(this);
if(btn_update != null)
btn_update.setOnClickListener(this);
if(btn_delete != null)
btn_delete.setOnClickListener(this);
}

@Override
public void onClick(View v) {
switch (v.getId()) {
case R.id.btn_insert:
ContentValues values1 = new ContentValues();
//name为数据库中属性名,第二个为欲插入的值
values1.put("name", "呵呵~" + i);
i++;
//参数依次是：表名，强行插入null值得数据列的列名，一行记录的数据
db.insert("person", null, values1);
Toast.makeText(mContext, "插入完毕~", Toast.LENGTH_SHORT).show();
break;
case R.id.btn_query:
StringBuilder sb = new StringBuilder();
//参数依次是:表名，列名，where约束条件，where中占位符提供具体的值，指定group by的列，进一步约束
//指定查询结果的排序方式
Cursor cursor = db.query("person", null, null, null, null, null, null);
if (cursor.moveToFirst()) {
do {
int id = cursor.getInt(cursor.getColumnIndex("_id"));
String name = cursor.getString(cursor.getColumnIndex("name"));
sb.append("id：" + id + "：" + name + "\n");
} while (cursor.moveToNext());
}
cursor.close();
Toast.makeText(mContext, sb.toString(), Toast.LENGTH_SHORT).show();
break;
case R.id.btn_update:
ContentValues values2 = new ContentValues();
values2.put("name", "嘻嘻~");
//参数依次是表名，修改后的值，where条件，以及约束，如果不指定三四两个参数，会更改所有行
db.update("person", values2, "name = ?", new String[]{"呵呵~2"});
break;
case R.id.btn_delete:
//参数依次是表名,where条件,约束
db.delete("person", "_id = ?", new String[]{"3"});
//多个条件
//                db.delete("person", "_id=? and name=?", new String[]{"1", "小名"});
break;
}
}
}

这里先创建一个数据库助手，通过该助手获取数据库操作对象。利用该对象提供的API来操作数据库。

数据库助手类

package xidian.dy.com.chujia;

import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;

/**
* Created by dy on 2016/6/13.
*/
public class MyDBOpenHelper extends SQLiteOpenHelper {
public MyDBOpenHelper(Context context, String name, SQLiteDatabase.CursorFactory factory,
int version) {super(context, "my.db", null, 1); }
@Override
//数据库第一次创建时被调用
public void onCreate(SQLiteDatabase db) {
db.execSQL("CREATE TABLE person(_id INTEGER PRIMARY KEY AUTOINCREMENT,name VARCHAR(20))");

}
//软件版本号发生改变时调用
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("ALTER TABLE person ADD phone VARCHAR(12) NULL");
}
}

事务

如果在数据库操作中使用到了事务可以参考以下的代码

//转账事物
public void transaction(){
try {
db.beginTransaction();
ContentValues values = new ContentValues();
values.put("salary", 9000);
db.update("person",values,"name=?", new String[]{"小王"});
values.clear();
values.put("salary", 11000);
db.update("person", values, "name=?", new String[]{"小张"});
//设置事务执行成功
db.setTransactionSuccessful();
}finally {
//关闭事物,同时提交,如果已经设置事务执行成功,那么sql将会生效,否则SQL回滚
db.endTransaction();
}
}