深入分析 Android ContentProvider (一) - IT评测·应用市场-qidao123.com技术社区

public class DatabaseHelper extends SQLiteOpenHelper {
private static final String DATABASE_NAME = "example.db";
private static final int DATABASE_VERSION = 1;
public static final String TABLE_NAME = "example";
public static final String COLUMN_ID = "_id";
public static final String COLUMN_NAME = "name";
private static final String TABLE_CREATE =
"CREATE TABLE " + TABLE_NAME + " (" +
COLUMN_ID + " INTEGER PRIMARY KEY AUTOINCREMENT, " +
COLUMN_NAME + " TEXT);";
public DatabaseHelper(Context context) {
super(context, DATABASE_NAME, null, DATABASE_VERSION);
}
@Override
public void onCreate(SQLiteDatabase db) {
db.execSQL(TABLE_CREATE);
}
@Override
public void onUpgrade(SQLiteDatabase db, int oldVersion, int newVersion) {
db.execSQL("DROP TABLE IF EXISTS " + TABLE_NAME);
onCreate(db);
}
}

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public class ExampleProvider extends ContentProvider {
private static final String AUTHORITY = "com.example.provider";
private static final String BASE_PATH = "example";
public static final Uri CONTENT_URI = Uri.parse("content://" + AUTHORITY + "/" + BASE_PATH);
private SQLiteDatabase database;
private static final String CONTENT_TYPE = "vnd.android.cursor.dir/vnd.example.example";
private static final String CONTENT_ITEM_TYPE = "vnd.android.cursor.item/vnd.example.example";
private static final int EXAMPLES = 1;
private static final int EXAMPLE_ID = 2;
private static final UriMatcher uriMatcher = new UriMatcher(UriMatcher.NO_MATCH);
static {
uriMatcher.addURI(AUTHORITY, BASE_PATH, EXAMPLES);
uriMatcher.addURI(AUTHORITY, BASE_PATH + "/#", EXAMPLE_ID);
}
@Override
public boolean onCreate() {
DatabaseHelper helper = new DatabaseHelper(getContext());
database = helper.getWritableDatabase();
return true;
}
@Nullable
@Override
public Cursor query(@NonNull Uri uri, @Nullable String[] projection, @Nullable String selection,
@Nullable String[] selectionArgs, @Nullable String sortOrder) {
Cursor cursor;
switch (uriMatcher.match(uri)) {
case EXAMPLES:
cursor = database.query(DatabaseHelper.TABLE_NAME, projection, selection, selectionArgs, null, null, sortOrder);
break;
case EXAMPLE_ID:
cursor = database.query(DatabaseHelper.TABLE_NAME, projection, DatabaseHelper.COLUMN_ID + "=?",
new String[]{String.valueOf(ContentUris.parseId(uri))}, null, null, sortOrder);
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
cursor.setNotificationUri(getContext().getContentResolver(), uri);
return cursor;
}
@Nullable
@Override
public String getType(@NonNull Uri uri) {
switch (uriMatcher.match(uri)) {
case EXAMPLES:
return CONTENT_TYPE;
case EXAMPLE_ID:
return CONTENT_ITEM_TYPE;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
}
@Nullable
@Override
public Uri insert(@NonNull Uri uri, @Nullable ContentValues values) {
long id = database.insert(DatabaseHelper.TABLE_NAME, null, values);
if (id > 0) {
Uri returnUri = ContentUris.withAppendedId(CONTENT_URI, id);
getContext().getContentResolver().notifyChange(returnUri, null);
return returnUri;
}
throw new SQLException("Failed to insert row into " + uri);
}
@Override
public int delete(@NonNull Uri uri, @Nullable String selection, @Nullable String[] selectionArgs) {
int rowsDeleted;
switch (uriMatcher.match(uri)) {
case EXAMPLES:
rowsDeleted = database.delete(DatabaseHelper.TABLE_NAME, selection, selectionArgs);
break;
case EXAMPLE_ID:
rowsDeleted = database.delete(DatabaseHelper.TABLE_NAME, DatabaseHelper.COLUMN_ID + "=?",
new String[]{String.valueOf(ContentUris.parseId(uri))});
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
if (rowsDeleted > 0) {
getContext().getContentResolver().notifyChange(uri, null);
}
return rowsDeleted;
}
@Override
public int update(@NonNull Uri uri, @Nullable ContentValues values, @Nullable String selection, @Nullable String[] selectionArgs) {
int rowsUpdated;
switch (uriMatcher.match(uri)) {
case EXAMPLES:
rowsUpdated = database.update(DatabaseHelper.TABLE_NAME, values, selection, selectionArgs);
break;
case EXAMPLE_ID:
rowsUpdated = database.update(DatabaseHelper.TABLE_NAME, values, DatabaseHelper.COLUMN_ID + "=?",
new String[]{String.valueOf(ContentUris.parseId(uri))});
break;
default:
throw new IllegalArgumentException("Unknown URI: " + uri);
}
if (rowsUpdated > 0) {
getContext().getContentResolver().notifyChange(uri, null);
}
return rowsUpdated;
}
}

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<provider
android:name=".ExampleProvider"
android:authorities="com.example.provider"
android:exported="true" />

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Uri uri = Uri.parse("content://com.example.provider/example");
Cursor cursor = getContentResolver().query(uri, null, null, null, null);
if (cursor != null) {
while (cursor.moveToNext()) {
String name = cursor.getString(cursor.getColumnIndexOrThrow("name"));
// 处理数据
}
cursor.close();
}

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ContentValues values = new ContentValues();
values.put("name", "Example Name");
Uri uri = Uri.parse("content://com.example.provider/example");
Uri newUri = getContentResolver().insert(uri, values);

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ContentValues values = new ContentValues();
values.put("name", "Updated Name");
Uri uri = Uri.parse("content://com.example.provider/example/1");
int rowsUpdated = getContentResolver().update(uri, values, null, null);

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Uri uri = Uri.parse("content://com.example.provider/example/1");
int rowsDeleted = getContentResolver().delete(uri, null, null);

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