Android SQLiteDatabase帮助类SQLiteOpenHelper的使用
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SQLiteOpenHelper是SQLiteDatabse的一个帮助类，用来管理数据的创建和版本更新。一般的用法是定义一个类继承SQLiteOpenHelper，并实现两个回调方法，OnCreate(SQLiteDatabase db)和onUpgrade(SQLiteDatabse, int oldVersion, int newVersion)来创建和更新数据库，我利用数据库做了一个类似电话本的功能，插入数据，查询数据，和删除数据，界面很丑，主要是讲解SQLiteOpenHelper类的用法，截图如下
首先我们创建一个DBHelper继承SQLiteOpenHelper，这个是数据库的一个帮助类
package com.example.utils;import android.content.ContentValues;import android.content.Context;import android.database.Cursor;import android.database.sqlite.SQLiteDatabase;import android.database.sqlite.SQLiteDatabase.CursorFactory;import android.database.sqlite.SQLiteOpenHelper;public class DBHelper extends SQLiteOpenHelper { private final static int VERSION = 1; private final static String DB_NAME = "phones.db"; private final static String TABLE_NAME = "phone"; private final static String CREATE_TBL = "create table phone(_id integer primary key autoincrement, name text, sex text, number text, desc text)"; private SQLiteDatabase db; //SQLiteOpenHelper子类必须要的一个构造函数 public DBHelper(Context context, String name, CursorFactory factory,int version) { //必须通过super 调用父类的构造函数 super(context, name, factory, version); } //数据库的构造函数，传递三个参数的 public DBHelper(Context context, String name, int version){ this(context, name, null, version); } //数据库的构造函数，传递一个参数的， 数据库名字和版本号都写死了 public DBHelper(Context context){ this(context, DB_NAME, null, VERSION); } // 回调函数，第一次创建时才会调用此函数，创建一个数据库 @Override public void onCreate(SQLiteDatabase db) { this.db = db; System.out.println("Create Database"); db.execSQL(CREATE_TBL); } //回调函数，当你构造DBHelper的传递的Version与之前的Version调用此函数 @Override public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) { System.out.println("update Database"); } //插入方法 public void insert(ContentValues values){ //获取SQLiteDatabase实例 SQLiteDatabase db = getWritableDatabase(); //插入数据库中 db.insert(TABLE_NAME, null, values); db.close(); } //查询方法 public Cursor query(){ SQLiteDatabase db = getReadableDatabase(); //获取Cursor Cursor c = db.query(TABLE_NAME, null, null, null, null, null, null, null); return c; } //根据唯一标识_id 来删除数据 public void delete(int id){ SQLiteDatabase db = getWritableDatabase(); db.delete(TABLE_NAME, "_id=?", new String[]{String.valueOf(id)}); } //更新数据库的内容 public void update(ContentValues values, String whereClause, String[]whereArgs){ SQLiteDatabase db = getWritableDatabase(); db.update(TABLE_NAME, values, whereClause, whereArgs); } //关闭数据库 public void close(){ if(db != null){ db.close(); } }}第一个MainActivity
package com.example.phonebooks;import android.app.Activity;import android.content.ContentValues;import android.content.Intent;import android.os.Bundle;import android.view.View;import android.view.View.OnClickListener;import android.widget.Button;import android.widget.EditText;import android.widget.RadioButton;import android.widget.RadioGroup;import android.widget.RadioGroup.OnCheckedChangeListener;import android.widget.Toast;import com.example.utils.DBHelper;public class MainActivity extends Activity implements OnClickListener{ private DBHelper dbHelper; //定义三个输入框 private EditText name, number, desc; //定义两个按钮 private Button submit ,look; //定义一个RadioGroup private RadioGroup radio; private String nameStr, numberStr, descStr; private String sexStr = "男"; @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); //实例化DBHelper dbHelper = new DBHelper(this); //根据id 获取到相对应的控件 name = (EditText)findViewById(R.id.editText1); number = (EditText)findViewById(R.id.editText2); desc = (EditText)findViewById(R.id.editText3); submit = (Button)findViewById(R.id.button1); look = (Button)findViewById(R.id.button2); radio = (RadioGroup)findViewById(R.id.radioGroup1); //按钮设置点击监听 submit.setOnClickListener(this); look.setOnClickListener(this); //单选群组的监听 radio.setOnCheckedChangeListener(new OnCheckedChangeListener() { @Override public void onCheckedChanged(RadioGroup group, int checkedId) { if(checkedId == R.id.radio0){ RadioButton r = (RadioButton) group.findViewById(checkedId); sexStr = r.getText().toString(); } if(checkedId == R.id.radio1){ RadioButton r = (RadioButton) group.findViewById(checkedId); sexStr = r.getText().toString(); } } }); } @Override public void onClick(View v) { switch (v.getId()) { case R.id.button1: if(name.getText().toString().length() != 0){ nameStr = name.getText().toString(); }else{ Toast.makeText(getApplication(), "姓名不能为空", Toast.LENGTH_SHORT).show(); return; } if(number.getText().toString().length() != 0){ numberStr = number.getText().toString(); }else{ Toast.makeText(getApplication(), "电话号码不能为空", Toast.LENGTH_SHORT).show(); return; } if(desc.getText().toString().length() != 0){ descStr = desc.getText().toString(); }else{ Toast.makeText(getApplication(), "备注不能为空", Toast.LENGTH_SHORT).show(); return; } //实例化一个ContentValues， ContentValues是以键值对的形式，键是数据库的列名，值是要插入的值 ContentValues values = new ContentValues(); values.put("name", nameStr); values.put("sex", sexStr); values.put("number", numberStr); values.put("desc", descStr); //调用insert插入数据库 dbHelper.insert(values); //将三个输入框重置下 reset(); break; case R.id.button2: Intent intent = new Intent(); intent.setFlags(Intent.FLAG_ACTIVITY_CLEAR_TOP); intent.setClass(this, ResultActivity.class); startActivity(intent); break; default: break; } } //重置edittext private void reset(){ name.setText(""); number.setText(""); desc.setText(""); }}activity_main.xml
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" android:background="#000000" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentTop="true" android:text="姓名" android:textSize="15dp" /> <EditText android:id="@+id/editText1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_below="@+id/textView1" android:ems="10" > <requestFocus /> </EditText> <RadioGroup android:id="@+id/radioGroup1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_below="@+id/editText1" > <RadioButton android:id="@+id/radio0" android:layout_width="wrap_content" android:layout_height="wrap_content" android:checked="true" android:text="男" /> <RadioButton android:id="@+id/radio1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignTop="@+id/radioGroup1" android:layout_toRightOf="@+id/textView2" android:text="女" /> </RadioGroup> <TextView android:id="@+id/textView2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_below="@+id/radioGroup1" android:text="电话号码" /> <EditText android:id="@+id/editText2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_below="@+id/textView2" android:ems="10" /> <TextView android:id="@+id/textView3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_below="@+id/editText2" android:text="备注" /> <EditText android:id="@+id/editText3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_below="@+id/textView3" android:lines="5" android:ems="10" android:inputType="textMultiLine" /> <Button android:id="@+id/button2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentBottom="true" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:text="查看" /> <Button android:id="@+id/button1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_below="@+id/editText3" android:text="插入" /></RelativeLayout>用一个Person类来封装姓名，性别，电话，备注这些数据。里面只有get()和set()方法package com.example.mode;public class Person { private String name; private String sex; private String number; private String desc; private int _id; public int get_id() { return _id; } public void set_id(int _id) { this._id = _id; } public String getName() { return name; } public void setName(String name) { this.name = name; } public String getSex() { return sex; } public void setSex(String sex) { this.sex = sex; } public String getNumber() { return number; } public void setNumber(String number) { this.number = number; } public String getDesc() { return desc; } public void setDesc(String desc) { this.desc = desc; }}查看数据的ResultActivitypackage com.example.phonebooks;import java.util.ArrayList;import java.util.List;import android.app.Activity;import android.app.AlertDialog;import android.content.Context;import android.content.DialogInterface;import android.content.DialogInterface.OnClickListener;import android.database.Cursor;import android.os.Bundle;import android.view.LayoutInflater;import android.view.View;import android.view.ViewGroup;import android.widget.AdapterView;import android.widget.AdapterView.OnItemClickListener;import android.widget.BaseAdapter;import android.widget.ListView;import android.widget.TextView;import com.example.mode.Person;import com.example.utils.DBHelper;public class ResultActivity extends Activity implements OnItemClickListener{ private ListView listView; private DbAdapter adapter; DBHelper dbHelper; List<Person> bookList = new ArrayList<Person>(); @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.result); //获取ListView listView = (ListView)findViewById(R.id.listView1); bookList = queryData(); //实例化DbAdapter adapter = new DbAdapter(getApplication(), bookList); listView.setAdapter(adapter); listView.setOnItemClickListener(this); } //查询数据库，将每一行的数据封装成一个person 对象，然后将对象添加到List中 private List<Person> queryData(){ List<Person> list = new ArrayList<Person>(); dbHelper = new DBHelper(this); //调用query()获取Cursor Cursor c = dbHelper.query(); while (c.moveToNext()){ int _id = c.getInt(c.getColumnIndex("_id")); String name = c.getString(c.getColumnIndex("name")); String sex = c.getString(c.getColumnIndex("sex")); String number = c.getString(c.getColumnIndex("number")); String desc = c.getString(c.getColumnIndex("desc")); //用一个Person对象来封装查询出来的数据 Person p = new Person(); p.set_id(_id); p.setName(name); p.setSex(sex); p.setNumber(number); p.setDesc(desc); list.add(p); } return list; } //自定义DbAdapter public class DbAdapter extends BaseAdapter{ private List<Person> list; private Context context; private LayoutInflater layoutInflater; public DbAdapter(Context context, List<Person> list){ layoutInflater = LayoutInflater.from(context); this.context = context; this.list = list; } //刷新适配器 public void refresh(List<Person> list){ this.list = list; notifyDataSetChanged(); } @Override public int getCount() { return list.size(); } @Override public Object getItem(int position) { return list.get(position); } @Override public long getItemId(int position) { return position; } @Override public View getView(int position, View convertView, ViewGroup parent) { Person p = list.get(position); ViewHolder holder; if(convertView == null){ holder = new ViewHolder(); convertView = layoutInflater.inflate(R.layout.item, null); holder.name = (TextView)convertView.findViewById(R.id.textView1); holder.sex = (TextView)convertView.findViewById(R.id.textView2); holder.number = (TextView)convertView.findViewById(R.id.textView3); holder.desc = (TextView)convertView.findViewById(R.id.textView4); convertView.setTag(holder); }else{ holder = (ViewHolder) convertView.getTag(); } holder.name.setText(p.getName()); holder.sex.setText(p.getSex()); holder.number.setText(p.getNumber()); holder.desc.setText(p.getDesc()); return convertView; } public class ViewHolder { public TextView name; public TextView sex; public TextView number; public TextView desc; public TextView id; } } @Override public void onItemClick(AdapterView<?> parent, View view, final int position, long id) { final Person p = bookList.get(position); final long temp = id; AlertDialog.Builder builder = new AlertDialog.Builder(this); builder.setMessage("真的要删除该记录？").setPositiveButton("是", new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { //调用delete（）删除某条数据 dbHelper.delete(p.get_id()); //重新刷新适配器 adapter.refresh(queryData()); } }).setNegativeButton("否", new OnClickListener() { @Override public void onClick(DialogInterface dialog, int which) { } }).create().show(); // 关闭数据库 dbHelper.close(); }}显示数据的布局result.xml,里面只有一个ListView<?xml version="1.0" encoding="UTF-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" > <ListView android:id="@+id/listView1" android:layout_width="fill_parent" android:layout_height="fill_parent" android:layout_alignParentLeft="true" android:cacheColorHint="#00000000" android:layout_alignParentTop="true" > </ListView></RelativeLayout>ListView 的item
<?xml version="1.0" encoding="UTF-8"?><RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="fill_parent" android:layout_height="fill_parent" > <TextView android:id="@+id/textView1" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentTop="true" android:text="TextView" /> <TextView android:id="@+id/textView3" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_above="@+id/textView4" android:layout_alignParentRight="true" android:text="TextView" /> <TextView android:id="@+id/textView2" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_above="@+id/textView4" android:layout_centerHorizontal="true" android:text="TextView" /> <TextView android:id="@+id/textView4" android:layout_width="wrap_content" android:layout_height="wrap_content" android:layout_alignParentLeft="true" android:layout_alignParentRight="true" android:layout_below="@+id/textView1" android:layout_marginTop="19dp" android:text="TextView" /></RelativeLayout>主要不要忘了在AndroidManifest.xml 注册ResultActivity 1 0
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