this.state = {text: ""};

<TextInput
                    style={{
                        height: 200,
                        width: 250,
                        fontSize: 15,
                        backgroundColor: 'white',
                    }}

                    editable = {true}
                    multiline = {true}
                    numberofLines = {4}
                    onChangeText={(text) => this.setState({text})}
                    value={this.state.text}
                />