ContentProvider实现跨程序数据共享，实例如下：
数据库基于数据存储中的使用的数据库，点击Here
1】ContentProvider类
public class ContentProvider extends android.content.ContentProvider {
private static final int BOOK_DIR = 0;
private static final int BOOK_ITEM = 1;
private static final int CATEGORY_DIR = 2;
private static final int CATEGORY_ITEM = 3;
private static final String AUTHORITY = "com.example.android.provider";
private static UriMatcher mUriMatcher;
private MyDatabaseHelper mHelper;
static {
mUriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
mUriMatcher.addURI(AUTHORITY, "book", BOOK_DIR);
mUriMatcher.addURI(AUTHORITY, "book/#", BOOK_ITEM);
mUriMatcher.addURI(AUTHORITY, "category", CATEGORY_DIR);
mUriMatcher.addURI(AUTHORITY, "category/#", CATEGORY_ITEM);
}
@Override
public boolean onCreate() {
mHelper = new MyDatabaseHelper(getContext(), "BookStore.db", null, 4);
return true;
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection, @Nullable String[] selectionArgs, @Nullable String sortOrder) {
SQLiteDatabase db = mHelper.getWritableDatabase();
Cursor cursor = null;
switch (mUriMatcher.match(uri)) {
case BOOK_DIR:
cursor = db.query("Book", projection, selection, selectionArgs, null, null, sortOrder);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
cursor = db.query("Book", projection, "id=?", new String[]{
bookId}, null, null, sortOrder);
break;
case CATEGORY_DIR:
cursor = db.query("Category", projection, selection, selectionArgs, null, null, sortOrder);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
cursor = db.query("Category", projection, "id=?", new String[]{
categoryId}, null, null, sortOrder);
break;
default:
break;
}
return cursor;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
switch (mUriMatcher.match(uri)) {
case BOOK_DIR:
return "vnd.android.cursor.dir/vnd.com.example.android.provider.book";
case BOOK_ITEM:
return "vnd.android.cursor.item/vnd.com.example.android.provider.book";
case CATEGORY_DIR:
return "vnd.android.cursor.dir/vnd.com.example.android.provider.category";
case CATEGORY_ITEM:
return "vnd.android.cursor.item/vnd.com.example.android.provider.category";
default:
break;
}
return null;
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
SQLiteDatabase db = mHelper.getWritableDatabase();
Uri uriRe = null;
switch (mUriMatcher.match(uri)) {
case BOOK_DIR:
case BOOK_ITEM:
long newBookId = db.insert("Book", null, values);
uriRe = Uri.parse("context://" + AUTHORITY + "/book" + newBookId);
break;
case CATEGORY_DIR:
case CATEGORY_ITEM:
long newCategoryId = db.insert("Category", null, values);
uriRe = Uri.parse("context://" + AUTHORITY + "/category" + newCategoryId);
break;
default:
break;
}
return uriRe;
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
SQLiteDatabase db = mHelper.getWritableDatabase();
int deleteRows = 0;
switch (mUriMatcher.match(uri)) {
case BOOK_DIR:
deleteRows = db.delete("Book", selection, selectionArgs);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
deleteRows = db.delete("Book", "id=?", new String[]{
bookId});
break;
case CATEGORY_DIR:
deleteRows = db.delete("Category", selection, selectionArgs);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
deleteRows = db.delete("Category", "id=?", new String[]{
categoryId});
break;
}
return deleteRows;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
SQLiteDatabase db = mHelper.getWritableDatabase();
int updateRows = 0;
switch (mUriMatcher.match(uri)) {
case BOOK_DIR:
updateRows = db.update("Book", values, selection, selectionArgs);
break;
case BOOK_ITEM:
String bookId = uri.getPathSegments().get(1);
updateRows = db.update("Book", values, "id=?", new String[]{
bookId});
break;
case CATEGORY_DIR:
updateRows = db.update("Category", values, selection, selectionArgs);
break;
case CATEGORY_ITEM:
String categoryId = uri.getPathSegments().get(1);
updateRows = db.update("Category", values, "id=?", new String[]{
categoryId});
break;
}
return updateRows;
}
}
2】实现增删改查
查询数据
private void queryData() {
Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY);
Cursor cursor = getContentResolver().query(uri, null, null, null, null, null);
if (cursor != null) {
while (cursor.moveToNext()) {
// 遍历Cursor对象，取出数据并打印
String category_name = cursor.getString(cursor.getColumnIndex("category_name"));
String category_code = cursor.getString(cursor.getColumnIndex("category_code"));
Log.d(TAG, "book name is " + category_name);
Log.d(TAG, "book author is " + category_code);
}
}
cursor.close();
}
更新数据
private void updateData() {
Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY);
ContentValues values = new ContentValues();
values.put("category_name", "科幻类");
values.put("category_code", 66);
getContentResolver().update(uri, values, "category_name=?", new String[]{
"科幻类"});
}
删除数据
private void deleteData() {
Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY + "/" + newId);
getContentResolver().delete(uri, null, null);
}
添加数据
private void InsertData() {
Uri uri = Uri.parse(AGREE + AUTHORITY + CATEGORY);
ContentValues values = new ContentValues();
values.put("category_name", "科幻类");
values.put("category_code", 11);
Uri newUri = getContentResolver().insert(uri, values);
newId = newUri.getPathSegments().get(1);
}
运行结果，查询数据pass，其他操作failed