一个简单通过SQLite 执行CRUD 的列表展示和编辑程序。
数据操作类
import java.util.Calendar;
import android.content.ContentValues;
import android.content.Context;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
public class DiaryDbAdapter {
//数据库名表名
private static final String DATABASE_NAME = "database";
private static final String DATABASE_TABLE = "diary";
private static final int DATABASE_VERSION = 1;
//字段属性
public static final String KEY_TITLE = "title";
public static final String KEY_BODY = "body";
public static final String KEY_ROWID = "_id";
public static final String KEY_CREATED = "created";
//操作对象
private DatabaseHelper mDbHelper;
//数据库本身
private SQLiteDatabase mDb;
//建库语句
private static final String DATABASE_CREATE = "create table diary (_id integer primary key autoincrement, "
+ "title text not null, body text not null, created text not null);";
//上下文对象
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
//自动执行
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(DATABASE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS diary");
onCreate(db);
}
}
//构造函数，初始化上下文
public DiaryDbAdapter(Context ctx) {
this.mCtx = ctx;
}
public DiaryDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase(); //获得一个可写数据库
return this;
}
//关闭数据库操作类
public void closeclose() {
mDbHelper.close();
}
//添加一条记录
public long createDiary(String title, String body) {
ContentValues initialValues = new ContentValues();
initialValues.put(KEY_TITLE, title);
initialValues.put(KEY_BODY, body);
Calendar calendar = Calendar.getInstance();
String created = calendar.get(Calendar.YEAR) + "年"
+ calendar.get(Calendar.MONTH) + "月"
+ calendar.get(Calendar.DAY_OF_MONTH) + "日"
+ calendar.get(Calendar.HOUR_OF_DAY) + "时"
+ calendar.get(Calendar.MINUTE) + "分";
initialValues.put(KEY_CREATED, created);
return mDb.insert(DATABASE_TABLE, null, initialValues);
}
//删除一条记录
public boolean deleteDiary(long rowId) {
return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
//获得所有数据并返回Cursor
public Cursor getAllNotes() {
return mDb.query(DATABASE_TABLE, new String[] { KEY_ROWID, KEY_TITLE,
KEY_BODY, KEY_CREATED }, null, null, null, null, null);
}
//获得一条数据，返回也是Cursor
public Cursor getDiary(long rowId) throws SQLException {
Cursor mCursor =
mDb.query(true, DATABASE_TABLE, new String[] { KEY_ROWID, KEY_TITLE,
KEY_BODY, KEY_CREATED }, KEY_ROWID + "=" + rowId, null, null,
null, null, null);
if (mCursor != null) {
mCursor.moveToFirst();
}
return mCursor;
}
//更新
public boolean updateDiary(long rowId, String title, String body) {
ContentValues args = new ContentValues();
args.put(KEY_TITLE, title);
args.put(KEY_BODY, body);
Calendar calendar = Calendar.getInstance();
String created = calendar.get(Calendar.YEAR) + "年"
+ calendar.get(Calendar.MONTH) + "月"
+ calendar.get(Calendar.DAY_OF_MONTH) + "日"
+ calendar.get(Calendar.HOUR_OF_DAY) + "时"
+ calendar.get(Calendar.MINUTE) + "分";
args.put(KEY_CREATED, created);
return mDb.update(DATABASE_TABLE, args, KEY_ROWID + "=" + rowId, null) > 0;
}
}
List 页面
import android.app.ListActivity;
import android.content.Intent;
import android.database.Cursor;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.ListView;
import android.widget.SimpleCursorAdapter;
/**
* @author jinyan
*
*/
public class ActivityMain extends ListActivity {
private static final int ACTIVITY_CREATE = 0;
private static final int ACTIVITY_EDIT = 1;
private static final int INSERT_ID = Menu.FIRST;
private static final int DELETE_ID = Menu.FIRST + 1;
private DiaryDbAdapter mDbHelper; //定义数据操作类，这个类在一个新的Java文件中定义
private Cursor mDiaryCursor; //数据存储集合
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.diary_list);
mDbHelper = new DiaryDbAdapter(this); //初始化数据对象
mDbHelper.open(); //打开将进行初始化，实例化一个数据库
renderListView(); //刷新ListView
}
private void renderListView() {
mDiaryCursor = mDbHelper.getAllNotes();
startManagingCursor(mDiaryCursor); //让数据被托管，这样可以垃圾回收
String[] from = new String[] { DiaryDbAdapter.KEY_TITLE,
DiaryDbAdapter.KEY_CREATED };//数据字段
int[] to = new int[] { R.id.text1, R.id.created }; //List控件 Id
SimpleCursorAdapter notes = new SimpleCursorAdapter(this,
R.layout.diary_row, mDiaryCursor, from, to); //绑定Cousor对象到List
setListAdapter(notes); //绑定当前List 数据
}
//重写草组偶菜单方法，建立菜单。
@Override
public boolean onCreateOptionsMenu(Menu menu) {
super.onCreateOptionsMenu(menu);
menu.add(0, INSERT_ID, 0, R.string.menu_insert);
menu.add(0, DELETE_ID, 0, R.string.menu_delete);
return true;
}
//菜单选择事件
@Override
public boolean onMenuItemSelected(int featureId, MenuItem item) {
switch (item.getItemId()) {
case INSERT_ID:
createDiary();
return true;
case DELETE_ID:
mDbHelper.deleteDiary(getListView().getSelectedItemId());
renderListView();
return true;
}
return super.onMenuItemSelected(featureId, item);
}
//插入事件代码，就是一个跳转
private void createDiary() {
Intent i = new Intent(this, ActivityDiaryEdit.class);
startActivityForResult(i, ACTIVITY_CREATE);
}
@Override
// 需要对position和id进行一个很好的区分
// position指的是点击的这个ViewItem在当前ListView中的位置
// 每一个和ViewItem绑定的数据，肯定都有一个id，通过这个id可以找到那条数据。
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Cursor c = mDiaryCursor; //定义一个临时变量
c.moveToPosition(position); //
Intent i = new Intent(this, ActivityDiaryEdit.class); //跳转到编辑页面
//写入参数
i.putExtra(DiaryDbAdapter.KEY_ROWID, id); //ID可以作为参数传进来
i.putExtra(DiaryDbAdapter.KEY_TITLE, c.getString(c
.getColumnIndexOrThrow(DiaryDbAdapter.KEY_TITLE)));
i.putExtra(DiaryDbAdapter.KEY_BODY, c.getString(c
.getColumnIndexOrThrow(DiaryDbAdapter.KEY_BODY)));
//调转带ID
startActivityForResult(i, ACTIVITY_EDIT);
}
//返回后刷新列表
@Override
protected void onActivityResult(int requestCode, int resultCode,
Intent intent) {
super.onActivityResult(requestCode, resultCode, intent);
renderListView();
}
}
编辑页面
import android.app.Activity;
import android.content.Intent;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
public class ActivityDiaryEdit extends Activity {
//初始化成员变量
private EditText mTitleText;
private EditText mBodyText;
private Long mRowId;
private DiaryDbAdapter mDbHelper; // 数据库操作类
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
//初始化数据操作控件
mDbHelper = new DiaryDbAdapter(this);
mDbHelper.open();
//设置页面
setContentView(R.layout.diary_edit);
//获得页面控件
mTitleText = (EditText) findViewById(R.id.title);
mBodyText = (EditText) findViewById(R.id.body);
Button confirmButton = (Button) findViewById(R.id.confirm);
mRowId = null;
// 每一个intent都会带一个Bundle型的extras数据。
Bundle extras = getIntent().getExtras();
//说明是编辑
if (extras != null) {
//获得传递过来的参数
String title = extras.getString(DiaryDbAdapter.KEY_TITLE);
String body = extras.getString(DiaryDbAdapter.KEY_BODY);
mRowId = extras.getLong(DiaryDbAdapter.KEY_ROWID);
//初始化控件
if (title != null) {
mTitleText.setText(title);
}
if (body != null) {
mBodyText.setText(body);
}
}
//设置保存事件
confirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String title = mTitleText.getText().toString();
String body = mBodyText.getText().toString();
//不等于空是修改，否则添加
if (mRowId != null) {
mDbHelper.updateDiary(mRowId, title, body);
} else
mDbHelper.createDiary(title, body);
Intent mIntent = new Intent();
setResult(RESULT_OK, mIntent);//设置点击按键
finish();//结束页面
}
});
}
}