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系出名門Android(9) - 數(shù)據(jù)庫支持(SQLite),

文章分類:移動開發(fā)

系出名門Android(9) - 數(shù)據(jù)庫支持(SQLite), 內容提供器(ContentProvider)

作者：webabcd

介紹
在 Android 中使用 SQLite, ContentProvider
數(shù)據(jù)庫支持(SQLite) - Android 開發(fā)平臺提供了操作 SQLite 數(shù)據(jù)庫的相關 API
內容提供器(ContentProvider) - 當數(shù)據(jù)需要在應用程序之間共享時，可以在某程序中使用 ContentProvider 定義 URI，以使其它應用程序可以通過此 URI 訪問指定的數(shù)據(jù)

1、SQLite 的 Demo
DatabaseHelper.java

Java代碼

代碼
package com.webabcd.SQLite;
import android.content.Context;
import android.database.sqlite.SQLiteDatabase;
import android.database.sqlite.SQLiteOpenHelper;
import android.database.sqlite.SQLiteDatabase.CursorFactory;
// 數(shù)據(jù)庫操作的 Helper 類
public class DatabaseHelper extends SQLiteOpenHelper {
DatabaseHelper(Context context, String name, CursorFactory cursorFactory, int version) {
super(context, name, cursorFactory, version);
}
@Override
public void onCreate(SQLiteDatabase db) {
// TODO 創(chuàng)建數(shù)據(jù)庫后，對數(shù)據(jù)庫的操作
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// TODO 更改數(shù)據(jù)庫版本的操作
}
@Override
public void onOpen(SQLiteDatabase db) {
super.onOpen(db);
// TODO 每次成功打開數(shù)據(jù)庫后首先被執(zhí)行
}
}
Main.java
代碼
package com.webabcd.SQLite;
import java.util.Random;
import android.app.Activity;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.SQLException;
import android.database.sqlite.SQLiteDatabase;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
public class Main extends Activity {
private DatabaseHelper dbHelper;
private static final String DATABASE_NAME = "db.db";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_NAME = "employee";
TextView txtMsg;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
dbHelper = new DatabaseHelper(this, DATABASE_NAME, null,
DATABASE_VERSION);
txtMsg = (TextView) this.findViewById(R.id.txtMsg);
Button btn1 = (Button) this.findViewById(R.id.btn1);
btn1.setText("創(chuàng)建表");
btn1.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
CreateTable();
}
});
Button btn2 = (Button) this.findViewById(R.id.btn2);
btn2.setText("插入 3 條記錄");
btn2.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
insertItem();
}
});
Button btn3 = (Button) this.findViewById(R.id.btn3);
btn3.setText("刪除全部記錄");
btn3.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
deleteItem();
}
});
Button btn4 = (Button) this.findViewById(R.id.btn4);
btn4.setText("更新指定數(shù)據(jù)");
btn4.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
updateItem();
}
});
Button btn5 = (Button) this.findViewById(R.id.btn5);
btn5.setText("顯示全部數(shù)據(jù)");
btn5.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
showItems();
}
});
Button btn6 = (Button) this.findViewById(R.id.btn6);
btn6.setText("刪除表");
btn6.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
dropTable();
}
});
}
// 創(chuàng)建數(shù)據(jù)表
private void CreateTable() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "CREATE TABLE IF NOT EXISTS " + TABLE_NAME
+ " (ID INTEGER PRIMARY KEY, Name VARCHAR, Age INTEGER);";
try {
db.execSQL(sql);
txtMsg.append("數(shù)據(jù)表成功創(chuàng)建\n");
} catch (SQLException ex) {
txtMsg.append("數(shù)據(jù)表創(chuàng)建錯誤\n" + ex.toString() + "\n");
}
}
// 插入數(shù)據(jù)
private void insertItem() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
Random random = new Random();
for (int i = 0; i < 3; i++) {
String sql = "insert into " + TABLE_NAME
+ " (name, age) values ('name" + String.valueOf(i)
+ "', " + random.nextInt() + ")";
// execSQL() - 執(zhí)行指定的 sql
db.execSQL(sql);
}
txtMsg.append("成功插入 3 條數(shù)據(jù)\n");
} catch (SQLException ex) {
txtMsg.append("插入數(shù)據(jù)失敗\n" + ex.toString() + "\n");
}
}
// 刪除數(shù)據(jù)
private void deleteItem() {
try {
SQLiteDatabase db = dbHelper.getWritableDatabase();
db.delete(TABLE_NAME, " id < 999999", null);
txtMsg.append("成功刪除數(shù)據(jù)\n");
} catch (SQLException e) {
txtMsg.append("刪除數(shù)據(jù)失敗\n");
}
}
// 更新數(shù)據(jù)
private void updateItem() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
try {
ContentValues values = new ContentValues();
values.put("name", "批量更新后的名字");
db.update(TABLE_NAME, values, "id<?", new String[] { "3" });
txtMsg.append("成功更新數(shù)據(jù)\n");
} catch (SQLException e) {
txtMsg.append("更新數(shù)據(jù)失敗\n");
}
}
// 查詢數(shù)據(jù)
private void showItems() {
SQLiteDatabase db = dbHelper.getReadableDatabase();
try {
String[] column = { "id", "name", "age" };
Cursor cursor = db.query(TABLE_NAME, column, null, null, null,
null, null);
Integer num = cursor.getCount();
txtMsg.append("共 " + Integer.toString(num) + " 條記錄\n");
cursor.moveToFirst();
while (cursor.getPosition() != cursor.getCount()) {
txtMsg.append(Integer.toString(cursor.getPosition()) + ","
+ String.valueOf(cursor.getString(0)) + ","
+ cursor.getString(1) + ","
+ String.valueOf(cursor.getString(2)) + "\n");
cursor.moveToNext();
}
} catch (SQLException ex) {
txtMsg.append("讀取數(shù)據(jù)失敗\n" + ex.toString() + "\n");
}
}
// 刪除數(shù)據(jù)表
private void dropTable() {
SQLiteDatabase db = dbHelper.getWritableDatabase();
String sql = "DROP TABLE IF EXISTS " + TABLE_NAME;
try {
db.execSQL(sql);
txtMsg.append("數(shù)據(jù)表刪除成功\n");
} catch (SQLException ex) {
txtMsg.append("數(shù)據(jù)表刪除錯誤\n" + ex.toString() + "\n");
}
}
}
2、ContentProvider 的 Demo
MyUser.java
代碼
package com.webabcd.contentprovider;
import android.net.Uri;
import android.provider.BaseColumns;
// 自定義 ContentProvider 所需的實體類
public class MyUser {
// 必須要有 _id 字段。本例中 BaseColumn 類中已經包含了 _id 字段
public static final class User implements BaseColumns {
// 定義 CONTENT_URI
public static final Uri CONTENT_URI = Uri.parse("content://com.webabcd.MyContentProvider");
// 表數(shù)據(jù)列
public static final String USER_NAME = "USER_NAME";
}
}
MyContentProvider.java
代碼
package com.webabcd.contentprovider;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import org.apache.http.util.EncodingUtils;
import android.content.ContentProvider;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.database.MatrixCursor;
import android.net.Uri;
// 繼承 ContentProvider 以實現(xiàn)自定義的 ContentProvider（基于文件的信息存儲）
public class MyContentProvider extends ContentProvider {
private File file;
private FileOutputStream out;
private FileInputStream in;
// ContentProvider 的刪除數(shù)據(jù)接口
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
@Override
public String getType(Uri uri) {
// TODO Auto-generated method stub
return null;
}
// ContentProvider 的插入數(shù)據(jù)接口
@Override
public Uri insert(Uri uri, ContentValues values) {
try {
out = new FileOutputStream(file);
out.write(values.getAsString(MyUser.User.USER_NAME).getBytes());
out.close();
int rowId = 0;
Uri rowUri = ContentUris.appendId(
MyUser.User.CONTENT_URI.buildUpon(), rowId).build();
getContext().getContentResolver().notifyChange(rowUri, null);
return rowUri;
} catch (Exception e) {
return null;
}
}
// 創(chuàng)建用于保存信息的文件
@Override
public boolean onCreate() {
try {
// 每個包中應用程序的私有目錄為：/data/data/包名/
// SD 卡目錄為：/sdcard
file = new File("/data/data/com.webabcd.contentprovider/",
"demo.txt");
if (!file.exists())
file.createNewFile();
return true;
} catch (Exception ex) {
return false;
}
}
// ContentProvider 的查詢數(shù)據(jù)接口
@Override
public Cursor query(Uri uri, String[] projection, String selection,
String[] selectionArgs, String sortOrder) {
String content;
try {
in = new FileInputStream(file);
int length = (int) file.length();
byte[] buffer = new byte[length];
in.read(buffer, 0, length);
content = EncodingUtils.getString(buffer, "UTF-8");
in.close();
String[] columns = new String[] { MyUser.User._ID, MyUser.User.USER_NAME };
MatrixCursor cur = new MatrixCursor(columns);
String[] values = new String[] { "0", content };
cur.moveToFirst();
cur.addRow(values);
return cur;
} catch (Exception e) {
return null;
}
}
// ContentProvider 的更新數(shù)據(jù)接口
@Override
public int update(Uri uri, ContentValues values, String selection,
String[] selectionArgs) {
// TODO Auto-generated method stub
return 0;
}
}
Main.java
代碼
package com.webabcd.contentprovider;
import java.util.Random;
import android.app.Activity;
import android.content.ContentUris;
import android.content.ContentValues;
import android.database.Cursor;
import android.net.Uri;
import android.os.Bundle;
import android.provider.Contacts;
import android.provider.Contacts.People;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;
/*
* 幾個常用的系統(tǒng)內置的 ContentProvider 如下：
* content://media/internal/images 這個URI將返回設備上存儲的所有圖片
* content://contacts/people/ 這個URI將返回設備上的所有聯(lián)系人信息
* content://contacts/people/45 這個URI返回單個結果（聯(lián)系人信息中ID為45的聯(lián)系人記錄）
*/
public class Main extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.main);
Button btn1 = (Button) this.findViewById(R.id.btn1);
btn1.setText("新增聯(lián)系人記錄");
btn1.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
Random random = new Random();
insertRecords("name" + String.valueOf(random.nextInt()), String
.valueOf(random.nextInt()));
}
});
Button btn2 = (Button) this.findViewById(R.id.btn2);
btn2.setText("查看聯(lián)系人記錄");
btn2.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
displayRecords();
}
});
Button btn3 = (Button) this.findViewById(R.id.btn3);
btn3.setText("清除聯(lián)系人記錄");
btn3.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
deleteRecords();
}
});
Button btn4 = (Button) this.findViewById(R.id.btn4);
btn4.setText("更新聯(lián)系人記錄");
btn4.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
// 此處只是演示，id 來自 People._ID ，可參見 displayRecords() 是如何獲取 id 的
int id = 0;
updateRecord(id, "修改后的name");
}
});
Button btn5 = (Button) this.findViewById(R.id.btn5);
btn5.setText("新增記錄到 MyContentProvider");
btn5.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
insertRecord2MyContentProvider("webabcd");
}
});
Button btn6 = (Button) this.findViewById(R.id.btn6);
btn6.setText("獲取記錄從 MyContentProvider");
btn6.setOnClickListener(new Button.OnClickListener() {
public void onClick(View v) {
displayRecord2MyContentProvider();
}
});
}
// 調用 ContentProvider 的插入接口
private void insertRecords(String name, String phoneNum) {
ContentValues values = new ContentValues();
values.put(People.NAME, name);
Uri uri = getContentResolver().insert(People.CONTENT_URI, values);
Log.d("MyDebug", uri.toString());
Uri numberUri = Uri.withAppendedPath(uri,
People.Phones.CONTENT_DIRECTORY);
Log.d("MyDebug", numberUri.toString());
values.clear();
values.put(Contacts.Phones.TYPE, People.Phones.TYPE_MOBILE);
values.put(People.NUMBER, phoneNum);
getContentResolver().insert(numberUri, values);
}
// 調用 ContentProvider 的查詢接口
private void displayRecords() {
String[] columns = new String[] { People._ID, People.NAME,
People.NUMBER };
Uri contacts = People.CONTENT_URI;
Log.d("MyDebug", contacts.toString());
Cursor cur = managedQuery(contacts, columns, // 要返回的數(shù)據(jù)字段
null, // WHERE子句
null, // WHERE 子句的參數(shù)
null // Order-by子句
);
if (cur.moveToFirst()) {
String id = null;
String name = null;
String phoneNo = null;
while (cur.getPosition() != cur.getCount()) {
id = cur.getString(cur.getColumnIndex(People._ID));
name = cur.getString(cur.getColumnIndex(People.NAME));
phoneNo = cur.getString(cur.getColumnIndex(People.NUMBER));
Toast.makeText(this, id + " / " + name + " / " + phoneNo,
Toast.LENGTH_SHORT).show();
cur.moveToNext();
}
}
}
// 調用 ContentProvider 的刪除接口
private void deleteRecords() {
Uri uri = People.CONTENT_URI;
Log.d("MyDebug", uri.toString());
getContentResolver().delete(uri, null, null);
// getContentResolver().delete(uri, "NAME=" + "'name'", null);
}
// 調用 ContentProvider 的更新接口
private void updateRecord(int recordNo, String name) {
Uri uri = ContentUris.withAppendedId(People.CONTENT_URI, recordNo);
Log.d("MyDebug", uri.toString());
ContentValues values = new ContentValues();
values.put(People.NAME, name);
getContentResolver().update(uri, values, null, null);
}
// 調用自定義 ContentProvider 的插入接口
private void insertRecord2MyContentProvider(String name) {
ContentValues values = new ContentValues();
values.put(MyUser.User.USER_NAME, name);
getContentResolver().insert(MyUser.User.CONTENT_URI, values);
}
// 調用自定義 ContentProvider 的查詢接口
private void displayRecord2MyContentProvider() {
String[] columns = new String[] { MyUser.User.USER_NAME };
Uri uri = MyUser.User.CONTENT_URI;
Cursor cur = managedQuery(uri, columns, null, null, null);
while (cur.getPosition() != cur.getCount()) {
String id = cur.getString(cur.getColumnIndex(People._ID));
String name = cur.getString(cur.getColumnIndex(MyUser.User.USER_NAME));
Toast.makeText(this,
id + " / " + name,
Toast.LENGTH_SHORT).show();
cur.moveToNext();
}
}
}
AndroidManifest.xml
代碼
<?xml version="1.0" encoding="utf-8"?>
<manifest xmlns:android="http://schemas.android.com/apk/res/android"
package="com.webabcd.contentprovider"
android:versionCode="1"
android:versionName="1.0">
<application android:icon="@drawable/icon" android:label="@string/app_name">
<activity android:name=".Main"
android:label="@string/app_name">
<intent-filter>
<action android:name="android.intent.action.MAIN" />
<category android:name="android.intent.category.LAUNCHER" />
</intent-filter>
</activity>
<!--
配置一個自定義的 ContentProvider"
-->
<provider android:name="MyContentProvider" android:authorities="com.webabcd.MyContentProvider" />
</application>
<uses-permission android:name="android.permission.WRITE_CONTACTS"></uses-permission>
<uses-permission android:name="android.permission.READ_CONTACTS"></uses-permission>
<uses-sdk android:minSdkVersion="3" />
</manifest>

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系出名門Android(9) - 數(shù)據(jù)庫支持(SQLite),