const testData =  [{
    label: 'kabel1',
    id: 1,
  },
  {
    label: 'label2',
    id: 2,
  },
  {
    label: 'label3',
    id: 3,
  }]

<AlphabetFlatList
          renderItem={this.renderItem}
          data={testData}
          getItemLayout={this.getItemLayout}
          keyExtractor={(item, index) => {
            return item.id;
          }}
          matchFieldName='label'
          mainFlatListContainerStyle={{ flex: 1 }}
          alphabetListProps={{
            selectedAlphabetTextStyle: {
              color: '#fff'
            },
            selectedAlphabetButtonStyle: {
              backgroundColor: '#312783',
              height: 50,
              width: 50,
              borderRadius: 25,
              shadowOpacity: 0.5,
              shadowOffset: { width: 2, height: 2 },
              elevation: 4
            },
            alphabetButtonStyle: {
              backgroundColor: '#fff',
              height: 50,
              width: 50,
              borderRadius: 25,
              shadowOpacity: 0.5,
              shadowOffset: { width: 2, height: 2 },
              elevation: 4
            },
            alphabetListContainerStyle: {
              flex: 0.2
            },
            showsVerticalScrollIndicator: false
          }}
        />