8.2 Android Basic 数据存储 Database SQLite Demo 2
SQLite Demo 2
本演练演示一个日记本程序
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新建项目SQLiteDemo2, 编辑res/layout/main.xml 文件
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk
/res/android"
android:layout_width="wrap_content" android:layout_height="wrap_content">
<ListView android:id="@+id/android:list" android:layout_width="wrap_content"
android:layout_height="wrap_content" />
<TextView android:id="@+id/android:empty"
android:layout_width="wrap_content" android:layout_height="wrap_content"
android:text="没有日记内容点击菜单开始写日记" />
</LinearLayout>
2. 在res/layout/ 新建布局文件 diary_row.xml 用于显示日记的界面：
<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout android:id="@+id/row"
xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView android:id="@+id/text1"
android:layout_width="wrap_content" android:layout_height="30px"
android:maxWidth="200dip"
android:textSize="22sp"
android:layout_marginTop="10dip"
android:text="标题" />
<TextView android:id="@+id/created" android:layout_width="wrap_content"
android:layout_height="35px" android:layout_alignParentRight="true"
android:layout_marginLeft="10dip"
android:layout_marginTop="10dip"
android:text="xxxx年xx月xx日" />
</RelativeLayout>
3. 在res/layout/新建布局文件 diary_edit.xml 用于编辑日记的界面
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical" android:layout_width="fill_parent"
android:layout_height="fill_parent">
<LinearLayout android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="wrap_content">
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content" android:text="@string/title"
android:padding="2px" />
<EditText android:id="@+id/title"
android:layout_width="fill_parent"
android:layout_height="wrap_content" android:layout_weight="1" />
</LinearLayout>
<TextView android:layout_width="wrap_content"
android:layout_height="wrap_content" android:text="@string/body" />
<EditText android:id="@+id/body" android:layout_width="fill_parent"
android:layout_height="fill_parent" android:layout_weight="1"
android:scrollbars="vertical" android:gravity="top" />
<Button android:id="@+id/confirm" android:text="@string/confirm"
android:layout_width="wrap_content"
android:layout_height="wrap_content" />
</LinearLayout>
4. 打开res/values/string.xml，添加如下内容：
<?xml version="1.0" encoding="utf-8"?>
<resources>
<string name="hello">Hello World, SQLiteDemo2!</string>
<string name="app_name">SQLiteDemo2</string>
<string name="menu_insert">添加一篇新日记</string>
<string name="menu_delete">删除一篇日记</string>
<string name="title">标题</string>
<string name="body">内容</string>
<string name="confirm">确定</string>
<string name="edit_diary">编辑日记</string>
</resources>
5. 新建DiaryDbAdapter类，用于封装对数据库的操作。
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 {
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";
private static final String TAG = "DiaryDbAdapter";
private DatabaseHelper mDbHelper;
private SQLiteDatabase mDb;
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);";
private static final String DATABASE_NAME = "database";
private static final String DATABASE_TABLE = "diary";
private static final int DATABASE_VERSION = 1;
private final Context mCtx;
private static class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@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);
}
}
public DiaryDbAdapter(Context ctx) {
this.mCtx = ctx;
}
public DiaryDbAdapter open() throws SQLException {
mDbHelper = new DatabaseHelper(mCtx);
mDb = mDbHelper.getWritableDatabase();
return this;
}
public void closeclose() {
mDbHelper.close();
}
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);
}
public boolean deleteDiary(long rowId) {
return mDb.delete(DATABASE_TABLE, KEY_ROWID + "=" + rowId, null) > 0;
}
public Cursor getAllNotes() {
return mDb.query(DATABASE_TABLE, new String[] { KEY_ROWID, KEY_TITLE,
KEY_BODY, KEY_CREATED }, null, null, null, null, null);
}
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;
}
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;
}
}
6. 新建类DiaryEditActivity类继承自Activity类用于编辑日记:
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 DiaryEditActivity extends Activity {
private EditText mTitleText;
private EditText mBodyText;
private Long mRowId;
private DiaryDbAdapter mDbHelper;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
mDbHelper = new DiaryDbAdapter(this);
mDbHelper.open();
setContentView(R.layout.diary_edit);
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();
if (extras != null) {
String title = extras.getString(DiaryDbAdapter.KEY_TITLE);
String body = extras.getString(DiaryDbAdapter.KEY_BODY);
mRowId = extras.getLong(DiaryDbAdapter.KEY_ROWID);
if (title != null) {
mTitleText.setText(title);
}
if (body != null) {
mBodyText.setText(body);
}
}
confirmButton.setOnClickListener(new View.OnClickListener() {
public void onClick(View view) {
String title = mTitleText.getText().toString();
String body = mBodyText.getText().toString();
if (mRowId != null) {
mDbHelper.updateDiary(mRowId, title, body);
} else
mDbHelper.createDiary(title, body);
Intent mIntent = new Intent();
setResult(RESULT_OK, mIntent);
finish();
}
});
}
}
7. 编辑SQLiteDemo2类
import android.app.Activity;
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;
public class SQLiteDemo2 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;
private Cursor mDiaryCursor;
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
mDbHelper = new DiaryDbAdapter(this);
mDbHelper.open();
renderListView();
}
private void renderListView() {
mDiaryCursor = mDbHelper.getAllNotes();
startManagingCursor(mDiaryCursor);
String[] from = new String[] { DiaryDbAdapter.KEY_TITLE,
DiaryDbAdapter.KEY_CREATED };
int[] to = new int[] { R.id.text1, R.id.created };
SimpleCursorAdapter notes = new SimpleCursorAdapter(this,
R.layout.diary_row, mDiaryCursor, from, to);
setListAdapter(notes);
}
@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;
}
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);
}
private void createDiary() {
Intent i = new Intent(this, DiaryEditActivity.class);
startActivityForResult(i, ACTIVITY_CREATE);
}
protected void onListItemClick(ListView l, View v, int position, long id) {
super.onListItemClick(l, v, position, id);
Cursor c = mDiaryCursor;
c.moveToPosition(position);
Intent i = new Intent(this, DiaryEditActivity.class);
i.putExtra(DiaryDbAdapter.KEY_ROWID, id);
i.putExtra(DiaryDbAdapter.KEY_TITLE, c.getString(c
.getColumnIndexOrThrow(DiaryDbAdapter.KEY_TITLE)));
i.putExtra(DiaryDbAdapter.KEY_BODY, c.getString(c
.getColumnIndexOrThrow(DiaryDbAdapter.KEY_BODY)));
startActivityForResult(i, ACTIVITY_EDIT);
}
@Override
protected void onActivityResult(int requestCode, int resultCode,
Intent intent) {
super.onActivityResult(requestCode, resultCode, intent);
renderListView();
}
}
8. 在AndroidManifest.xml 中配置
<activity android:name="DiaryEditActivity"></activity>
