Gson fails to convert ContentValues with Android 10

The internal implementation of ContentValues changed from using a Hashmap to using an ArrayMap in Android 10. I’ve included some sample code below to demonstrate how it fails now.

ContentValues values = new ContentValues();
values.put("Key 1", "Key 1 value");
values.put("Key 2", "Key 2 value");
values.put("Key 3", "Key 3 value");
String json = new Gson().toJson(values);
Log.d("XXX", String.format("Content values json: '%s'", json));

On Android 10 the output looks like: Output: XXX: Content values json: ‘{}’

On Android 9 the output looks like: Output: XXX: Content values json: {“mValues”:{“Key 1”:“Key 1 value”,“Key 2”:“Key 2 value”,“Key 3”:“Key 3 value”}}

[lyubomyr-shaydariv]

@tethridge

I’m not into the Android API, but I don’t really believe using Gson for this case is a good choice. (Except probably an attempt of nesting/packing some data as string values, however Parcelable looks like a (de)serialization tool already.) If you still need using Gson, you probably might fine-tune the example below (avoid intermediate maps, avoid the map type adapter and use readers/writers directly, etc):

@SuppressWarnings("all")
class FakeContentValues {

	private final Map<String, Object> mValues = new LinkedHashMap<>();

	FakeContentValues() {
	}

	// @formatter:off
	void putNull(final String key) { mValues.put(key, null); }
	void put(final String key, final Short value) { mValues.put(key, value); }
	void put(final String key, final Long value) { mValues.put(key, value); }
	void put(final String key, final Double value) { mValues.put(key, value); }
	void put(final String key, final Integer value) { mValues.put(key, value); }
	void put(final String key, final String value) { mValues.put(key, value); }
	void put(final String key, final Boolean value) { mValues.put(key, value); }
	void put(final String key, final Float value) { mValues.put(key, value); }
	void put(final String key, final byte[] value) { mValues.put(key, value); }
	void put(final String key, final Byte value) { mValues.put(key, value); }
	Object get(final String key) { return mValues.get(key); }
	Set<String> keySet() { return mValues.keySet(); }
	// @formatter:on

	@Override
	public boolean equals(final Object o) {
		if ( this == o ) {
			return true;
		}
		if ( o == null || getClass() != o.getClass() ) {
			return false;
		}
		final FakeContentValues that = (FakeContentValues) o;
		return mValues.equals(that.mValues);
	}

	@Override
	public int hashCode() {
		return mValues.hashCode();
	}

	@Override
	public String toString() {
		return "{mValues=" + mValues + "}";
	}

}

private static final Gson gson = new GsonBuilder()
	.disableHtmlEscaping()
	.disableInnerClassSerialization()
	.registerTypeAdapterFactory(new TypeAdapterFactory() {
		@Override
		@SuppressWarnings("ReturnOfNull")
		public <T> TypeAdapter<T> create(final Gson gson, final TypeToken<T> typeToken) {
			final Class<? super T> rawType = typeToken.getRawType();
			if ( !FakeContentValues.class.isAssignableFrom(rawType) ) {
				return null;
			}
			final TypeAdapter<LinkedHashMap<String, Object>> delegateTypeAdapter = gson.getDelegateAdapter(this, mapStringToObjectTypeToken);
			final TypeAdapter<FakeContentValues> typeAdapter = new TypeAdapter<FakeContentValues>() {
				@Override
				public void write(final JsonWriter out, final FakeContentValues contentValues)
						throws IOException {
					final LinkedHashMap<String, Object> intermediate = new LinkedHashMap<>();
					for ( final String key : contentValues.keySet() ) {
						intermediate.put(key, contentValues.get(key));
					}
					delegateTypeAdapter.write(out, intermediate);
				}

				@Override
				@SuppressWarnings("IfStatementWithTooManyBranches")
				public FakeContentValues read(final JsonReader in)
						throws IOException {
					final Map<String, Object> intermediate = delegateTypeAdapter.read(in);
					final FakeContentValues contentValues = new FakeContentValues();
					for ( final Map.Entry<String, Object> e : intermediate.entrySet() ) {
						final String k = e.getKey();
						final Object v = e.getValue();
						// @formatter:off
						if ( v == null ) { contentValues.putNull(k); }
						else if ( v instanceof Short ) { contentValues.put(k, (Short) v); }
						else if ( v instanceof Long ) { contentValues.put(k, (Long) v); }
						else if ( v instanceof Double ) { contentValues.put(k, (Double) v); }
						else if ( v instanceof Integer ) { contentValues.put(k, (Integer) v); }
						else if ( v instanceof String ) { contentValues.put(k, (String) v); }
						else if ( v instanceof Boolean ) { contentValues.put(k, (Boolean) v); }
						else if ( v instanceof Float ) { contentValues.put(k, (Float) v); }
						else if ( v instanceof byte[] ) { contentValues.put(k, (byte[]) v); }
						else if ( v instanceof Byte ) { contentValues.put(k, (Byte) v); }
						else { throw new UnsupportedOperationException(String.valueOf(v.getClass())); }
						// @formatter:on
					}
					return contentValues;
				}
			};
			@SuppressWarnings("unchecked")
			final TypeAdapter<T> castTypeAdapter = (TypeAdapter<T>) typeAdapter;
			return castTypeAdapter;
		}
	})
	.create();

final FakeContentValues before = new FakeContentValues();
before.put("Key 1", "Key 1 value");
before.put("Key 2", "Key 2 value");
before.put("Key 3", "Key 3 value");
System.out.println("before=" + before);
final String json = gson.toJson(before);
System.out.println(json);
final FakeContentValues after = gson.fromJson(json, FakeContentValues.class);
System.out.println("after=" + after);
System.out.println("equals=" + before.equals(after));

gives

before={mValues={Key 1=Key 1 value, Key 2=Key 2 value, Key 3=Key 3 value}}
{"Key 1":"Key 1 value","Key 2":"Key 2 value","Key 3":"Key 3 value"}
after={mValues={Key 1=Key 1 value, Key 2=Key 2 value, Key 3=Key 3 value}}
equals=true

[tethridge]

Thanks for the feedback. I’ll close this issue. I resolved the issue in my app by implementing my own serialization code.