以下是一个使用查询方法进行插入、删除和更新的Android内容提供程序的解决方法,包含了代码示例。
首先,创建一个自定义的ContentProvider类,继承自ContentProvider,并实现必要的方法。
public class MyContentProvider extends ContentProvider {
// 定义数据库相关的常量
private static final String DATABASE_NAME = "mydb";
private static final int DATABASE_VERSION = 1;
private static final String TABLE_NAME = "mytable";
// 定义URI和URI匹配模式的常量
private static final String AUTHORITY = "com.example.mycontentprovider";
private static final String CONTENT_URI_BASE = "content://" + AUTHORITY;
private static final String CONTENT_URI_STRING = CONTENT_URI_BASE + "/" + TABLE_NAME;
public static final Uri CONTENT_URI = Uri.parse(CONTENT_URI_STRING);
// 定义数据库操作的常量
private static final int URI_MATCH_ALL = 1;
private static final int URI_MATCH_ITEM = 2;
// 定义数据库操作的帮助类
private DatabaseHelper databaseHelper;
// 创建数据库操作的帮助类
private static class DatabaseHelper extends SQLiteOpenHelper {
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
// 创建数据库表
String createTable = "CREATE TABLE " + TABLE_NAME + " (_id INTEGER PRIMARY KEY, name TEXT)";
db.execSQL(createTable);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
// 升级数据库表
String dropTable = "DROP TABLE IF EXISTS " + TABLE_NAME;
db.execSQL(dropTable);
onCreate(db);
}
}
@Override
public boolean onCreate() {
// 初始化数据库操作的帮助类
databaseHelper = new DatabaseHelper(getContext());
return true;
}
@Override
public Cursor query(Uri uri, String[] projection, String selection, String[] selectionArgs, String sortOrder) {
// 根据URI匹配模式进行不同的查询操作
SQLiteDatabase db = databaseHelper.getWritableDatabase();
Cursor cursor;
switch (URI_MATCHER.match(uri)) {
case URI_MATCH_ALL:
cursor = db.query(TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
break;
case URI_MATCH_ITEM:
String id = uri.getLastPathSegment();
String where = "_id=" + id + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
cursor = db.query(TABLE_NAME, projection, where, selectionArgs, null, null, sortOrder);
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;
}
@Override
public Uri insert(Uri uri, ContentValues values) {
// 插入数据
SQLiteDatabase db = databaseHelper.getWritableDatabase();
long rowId = db.insert(TABLE_NAME, null, values);
if (rowId > 0) {
Uri insertUri = ContentUris.withAppendedId(CONTENT_URI, rowId);
getContext().getContentResolver().notifyChange(insertUri, null);
return insertUri;
}
throw new SQLException("Failed to insert row into " + uri);
}
@Override
public int delete(Uri uri, String selection, String[] selectionArgs) {
// 删除数据
SQLiteDatabase db = databaseHelper.getWritableDatabase();
int count;
switch (URI_MATCHER.match(uri)) {
case URI_MATCH_ALL:
count = db.delete(TABLE_NAME, selection, selectionArgs);
break;
case URI_MATCH_ITEM:
String id = uri.getLastPathSegment();
String where = "_id=" + id + (!TextUtils.isEmpty(selection) ? " AND (" + selection + ')' : "");
count = db.delete(TABLE_NAME, where, selectionArgs);
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
getContext().getContentResolver().notifyChange(uri, null);
return count;
}
@Override
public int update(Uri uri, ContentValues values, String selection, String[] selectionArgs) {
// 更新数据
SQLiteDatabase db = databaseHelper.getWritableDatabase();
int count;
switch (URI_MATCHER.match(uri)) {
case URI_MATCH_ALL:
count = db.update(TABLE_NAME, values, selection, selectionArgs);
break;
case URI_MATCH_ITEM:
String id = uri.getLastPathSegment();